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Letter to the Editor

by Robert D. Phillips, DPM1

1 – Orlando Veterans Administration Medical Center


Dear Sir,

I read with interest in the March issue the article by Glaser and Fleming, “Foot Posture Biomechanics and MASS Theory.”  If this article had appeared in a non-refereed magazine, I probably would not have said much, however since The Foot and Ankle Online Journal purports to be a refereed journal, with peer review of submitted articles, I am going to have to chide the reviewers for allowing an article with such sloppy scholarliness slip by them.  The article with riddled with gross misstatements about what Dr. Merton Root taught, poor interpretation of the limited literature it presented as references, and poor thought logic and reasoning, and statements of authoritative opinion that have less research to back them up than the opinions of Root they supposedly tear down.

Let’s first of all look at some of the outright misstatements about the theories of Merton L. Root

  1. In the very first paragraph, the authors state, “He [Root] discovered that by placing the patient prone while holding the off weight bearing foot in a palpated, “neutral” position, it was observed that most heels were inverted; rearfoot varus.”  

Nowhere in the cited reference does Root make such a statement, though he does say that rearfoot varus is one of the common causes of excessive subtalar joint pronation (p.298) and also that compensation for rearfoot varus did not usually produce highly pathological conditions as the subtalar joint would still resupinate after heel off (p 313) [1].

Now, it is true that some of Root’s contemporaries have taught that most people have rearfoot varus.  This particular writer has heard many times such theory from colleagues, e.g. Dr. Chris Smith, however Root himself did not did not teach this. Phillips and Phillips (1983) found in the average patient in their series had 1.5° of subtalar varus [2]. McPoil et al. (1988) reported that 84% of young females had subtalar varus, with 41% less than 4° and 41% between 4°-8° [3]. On the other hand Åström and Arvidson (1995) reported the average person had 2° of subtalar valgus [4].  

It should be pointed out that Root never believed that the average person represented the normal foot.  A full and most scholarly discussion of Root’s concept of normal can be found in the historical treatise by Lee of the Root concepts (2001) [5].

  1. The authors go on to state, “Root recommended taking 17 measurements called the Static Biomechanical Exam [2]”.

Root did not call the examination “the Static Biomechanical Exam”.  He called the form, “Biomechanical Exam of Lower Extremities.”  The exam is broken into 7 basic areas, the metatarsus, the midfoot, the rearfoot, the ankle joint, the lower leg, the hip, and a static functional test.  The word ‘static’ could possibly be applied to three fixed measurements, i.e. the malleolar torsion, the forefoot to rearfoot relationship and the tibial angulation with the ground.  The others are ranges of motion wherein the joints have capability to function.  Therefore we could state that part of the exam is static, part is functional ranges and part is measure of function.  In addition to taking goniometric measurements, he also advocated extensive and complete muscle testing.

  1. The authors state, “Treatment was aimed at correcting what was viewed as a frontal plane deformity with frontal plane correction of the rearfoot and forefoot, called posts, designed to encourage the foot into a more neutral rotational position around the subtalar joint (STJ) axis.”

There are several errors in this one sentence.  First of all treatment was aimed at stabilizing the midtarsal joint by capturing the plantar foot shape in a nonweightbearing state, and using a “rigid” material to push the midtarsal joint toward this state.  The stable state of the midtarsal joint is based on the twisted plate theory, first advocated by Steindler (1929) [6]. This twisted plate theory of function was rejected by Schuster (1976) [7] The orthotic did not correct the forefoot or rearfoot, it merely tried to support either the medial or lateral side of the forefoot off the floor when the subtalar joint was in neutral.  This support platform is called the forefoot post. The rearfoot post was added much later to make the orthotic more stable in the shoe, not to make any corrections.

The authors try to confuse the reader with their last phrase, utilizing terminology that is redundant jargon. All researchers of subtalar joint motion papers have maintained that there is an axis for the joint to move around.  Variations in methodology have disagreed as to whether the motion is a strict axis motion [8], a moving joint axis [9] or a helical motion [10]. Whichever it is, it is unknown what a “neutral rotational position is.”  Root did state that a majority (not all) orthotics should push the subtalar joint closer to its neutral position, not because the heel was more stable, but because the midtarsal joint is more stable when the subtalar joint is in neutral position.

  1. The authors state, “Neutral position, which Root defined as “neither pronated nor supinated”, is simply a rotational position around a singular axis; the subtalar joint axis.  Pronation and supination are defined in both the open and closed chains as rotations around this singular axis.”

The authors are very imprecise in their discussion of Root theory, and in doing so they muddy the reader’s minds as to what Root stated.  Root stated that there is a neutral position of the subtalar joint.  He also stated that there were neutral positions of other foot joints, including the hip joint, the ankle joint and the first ray.  He discussed pronation around the subtalar joint during gait, as well as pronation around the oblique axis of the midtarsal joint and the long axis of the midtarsal joint.  It is important to realize that pronation of the subtalar joint in closed kinetic chain is passively accompanied by pronation around the oblique axis of the midtarsal joint and supination around the long axis of the midtarsal joint.  These three motions are seen as a single motion, which Nester described as motion around a single axis that moves (1997) [11].

  1. The authors make the following statements regarding what Root taught about how many axes there are in the foot: “The extreme of single axis theory is to imagine that the foot only has one axis and consider the foot as just two rigid bodies teetering around this singular axis.  This model concerns itself with the distribution of kinetic forces and their perpendicular distance to this one axis.  This describes the Subtalar Axis Location and Rotational Equilibrium (SALRE) theory of Kevin Kirby, DPM.” …  “The basic difference between single axis models, such as the STJ Neutral Model, and a postural model is that single axis models, by definition, ignore the rest of the foot” …. “The basic difference between single axis models, such as the STJ Neutral Model, and a postural model is that single axis models, by definition, ignore the rest of the foot.  You can find STJ neutral in a broad range of foot postures both in the open and closed kinetic chain.”

These statements are a gross misrepresentation of both Root and Kirby.  As noted above, Root never described motion of the foot as occurring around a single axis.  Root described motion of the foot as occurring around multiple joint axis, including motion around the subtalar joint, the midtarsal joint, the ankle joint, the first and fifth ray joints and motion around the metatarsophalangeal joints. Kirby likewise never said that the foot rotates around one axis, though he most often writes and talks about the subtalar joint axis, so that the casual reader or listener may believe that he believes there is only one axis of motion for the entire foot.

  1. The authors somehow believe they have discovered something unique with these statements.  “Posture is simply stepping back and looking at the foot as a whole and observing the way elevation of the longitudinal arches causes bones to nest into each other in a more closed pack position.  Paul Jones attributes this to a generalized spiral twisting of the forefoot on the rearfoot, The Wring Theory [11].  Sarrafian described the frontal plane forefoot to rearfoot relationship as a twisted plate. All of these models are posture based [13].  Posture is the All Axis Model.”

Root was very much a twisted plate theorist, though he may not have ever used those exact words.  Forefoot varus had been described in the literature before Root, however this writer has not found any previous author who described forefoot valgus [12].  Root was the one who proposed that a pathology of the forefoot to the rearfoot could be only be diagnosed if the entire range of midtarsal joint motion had been utilized in the pronation direction.  Posture of the foot in static stance and also function of the foot was partially dictated by these forefoot to rearfoot relationships and available motions.

  1. The authors then make the following statement: “The small amount of STJ rotation is where Merton Root and Kevin Kirby concentrated their attention [4].  According to Root’s own measurements the total range of STJ rotation in ideal gait is only six degrees (+2 to -4).”

First of all, Root never took measurements of the foot motion in ideal gait, though he did measure range of motion available for the subtalar joint to move within and also the static subtalar joint position in stance.  As to gait, Root looked to the best literature of his time for information about the range of motion of the subtalar joint during gait [13,14]. Since then, multiple authors have shown that Root’s proposal of the range of subtalar joint motion that the foot utilizes during gait is basically correct [15-19]. All authors, including Root, have agreed that subtalar joint motion when the heel is on the ground is small, but that once the heel comes off the ground, during propulsion, it is significantly more.

  1. The authors make the following statements: “Traditional orthotics based on the single axis models tend to be rather low in posture.  The cast is taken in a partially pronated position and then the arch is further lowered to varying degrees to make the orthotic tolerable.   Filling in, or lowering the arch of the orthotic, is often called ‘cast correction’ even though it divorces the geometry of the foot from the geometry of the orthoses and allows for greater postural collapse before the orthotic is contacted by the arch.”

What do the authors mean that the cast is taken in a partially pronated position?  The Root technique takes a typical cast with the subtalar joint in neutral position and the midtarsal joint in its fully pronated position.  This was the truly innovative idea that Root proposed, that the orthotic should have a supinatory effect on the subtalar joint and a pronatory effect on the midtarsal joint [20].  I haven’t read of anybody advocating taking a partially pronated cast.  It is true that many orthotic laboratories excessively lower the arches of the orthotic casts they receive.  This is not “cast correction” as the authors maintain.  

I recommend to the authors the following text by Dr. Root:  “Plaster modifications for the standard functional orthosis consist of the balance platforms beneath the first and fifth metatarsal heads, a filler between these platforms, a lateral expansion, and a medial arch filler….” “The lateral expansion of plaster is designed to accommodate the slight bulging of soft tissue all along the lateral side of the foot and around the lateral and posterior aspect of the heel. This prevents the orthosis from pinching this soft tissue, which occurs in a significant percentage of feet if a lateral expansion is not used”…. “The plaster medial arch filler is designed to flare the medial edge of the orthosis away from the medial arch of the foot to prevent the edge of the orthosis from cutting into the foot. It initially was used only on feet with a fairly large angle of forefoot adductus because such feet have a sharp angle in the medial arch in the area of the midtarsal and tarso-metatrasal joint. It was not possible to train technicians or new practitioners to recognize when this medial arch filler would be necessary. As a result, a filler was standardized that could be used on any foot without interfering with function of the orthosis.  The medial arch filler should extend form about mid-shaft of the first metatarsal and no farther posteriorly than the midtarsal joint. The filler should extend laterally in the arch of the foot to a line slightly lateral to where the medial edge of the finished orthosis will sit when placed on the cast” [21].

We can see from Root’s own description, the medial expansion was not intended to lower the medial arch but rather to flare only the very medial aspect of the medial edge away from the soft tissue. Many laboratories use the medial expansion as an accommodation for practitioners who send a tremendous number of casts taken with the long axis of the midtarsal joint supinated, or the first ray dorsiflexed or the lateral column plantarflexed.  This is a business decision by these companies to accept casts that are of poor quality and then produce a device that does not hurt the patient.  It does reflect on the poor practices of a great many clinicians in this country.

This writer has also made some observations about the advantages of the true Root orthotic flaring the orthotic away from the most medial edge of the arch of the foot.  One of these is that the orthotic must allow normal pronation to occur during the contact period of gait.  Second is that the lateral column is more flexible than the medial column.  Therefore when the orthotic is made of uniform thickness, the lateral column of the orthotic flexes more than the medial column, which supinates the long axis of the midtarsal joint and makes the orthotic more uncomfortable on the medial side.  If the clinician makes the lateral column thicker than the medial column, then equal flexes of both columns can be achieved and the orthotic lab does not have to artificially lower the medial arch.  Again it should be emphasized that the Root orthotic is not an arch support — it is a dynamic torsional device, intended to provide an inversion force on the rearfoot, with support under the sustentaculum tali, and to evert the forefoot against the rearfoot.

Let’s look at some of the poor representation of the literature used to support the authors’ contentions that the theories of Root should be discarded.

  1. The authors state the following: “Root et al, called Royal Whitman’s observation the phenomena of midtarsal locking and unlocking and attributed it to Elftman’s theory, that the talonavicular and calcaneocuboid axis deviated as the foot supinated [9].  Thus, this decreased the range of motion and parallelism of the axes, results in increased range of motion.”

The authors correctly state that in 1971, at the publication of their first book, Root et al did believe in the “locking” position mechanism proposed by Elftman, however by the time of their 1977 seminal publication, Root et al. had discarded the theory of Elftman as why the midtarsal joint had a smaller range of motion when the subtalar joint was in a supinated position than when it was in a pronated position.  The authors would find a detailed account of first the acceptance and then the rejection of the Manter theory by Root in the exhaustive work by Lee on the history of Root’s ideas (2001) [5].

  1. The authors make the following argument: “The STJ axis exits the foot at the same point; the momentum down the leg similarly point; the momentum down the leg similarly passes its force vector down the center of the dome of the talus thereby intersecting the STJ axis..  The ground reactive force enters the foot ideally on the plantar posterior lateral aspect of the heel asses its force vector down the center of the dome of the talus thereby intersecting the STJ axis.  The STJ axis is placed in an orientation that passes through the major forces entering the foot at heel contact, other than the force of friction which is horizontal and causes the forward roll of the calcaneus.”

The authors seem to be oblivious to the paper by Phillips and Lidtke (1992) that shows that the subtalar joint axis does not exit the foot at the posterior-lateral-inferior edge of the calcaneal fat pad, but instead intersects the posterior calcaneus between 4-5 cm above the inferior edge, and it intersects the ground approximately 5 cm posterior to the heel.  This means that the actual point of contact at the initiation of the gait cycle is actually lateral to the subtalar joint axis.  What the authors also fail to realize is that there is a significant shear force, directed laterally during contact, created by the internal rotation of the leg.  While this shear force may be only about 10% of the vertical force, it has between 5-10 times the lever arm with the subtalar joint axis, so that it has an angle that is more perpendicular to the subtalar joint axis than the vertical ground force.  This means that the horizontal, laterally directed shear force produces at least 50% of the total pronation torque around the subtalar joint axis.  The authors try to confuse the reader with their description of what the shear forces do.  The posterior shear force rolls the calcaneus forward at the ankle joint, not the subtalar joint.  Readers will find a detailed description of what how the vertical, the medial-lateral and the anterior-posterior ground forces affect each joint of the lower extremity, from the hip to the toe through the entire gait cycle, in the chapter on biomechanics by this writer in the text, Principles and Practices of Podiatric Medicine (2007) [23].

  1. The authors make the following statement: “Tom McPoil’s Tissue Stress Theory states that when microtrauma occurs faster than a person’s ability to heal, they experience a symptom.  During the last few degrees of postural collapse tissue stresses are highest.  Microtrauma occurring in this zone of foot posture causes symptoms.”

Those who claim to be “Tissue-Stress Theory” advocates, fail to recognize that Root was also a tissue stress advocate. Just a couple of quotes from his major work demonstrate this.  For example on page 229 we find, “The everted calcaneal position, which results from pronation that compensates a forefoot varus deformity, causes … a significant everting rotary moment that causes further pronation of the subtalar joint … The inherent arch structure of the foot begins to collapse, and ligamentous stretching and strain ensues.  The entire rearfoot becomes unstable.”   Later on page 326 we find, “The weightbearing forces move the joint either beyond its normal range of motion, or in a direction other than its normal plane of motion.  In either event, the ligaments are immediately placed under tension.  Since ligaments are elastic, they continue to elongate as long as the subluxing force is unresisted, and the articular surfaces separate slightly or may even dislocate with time.”

This writer often personally heard Root say that one only had block the last 1°-2° of subtalar joint pronation to alleviate a patient’s symptoms.  Certainly a great many papers have shown that a great many “Root-type” orthotics only prevent about 2°-3° of calcaneal eversion [24-27]. Therefore it is evident that the majority of the studies on the “Root” orthotics are documenting a marked decrease in symptoms with only small changes in kinematics, which supports the idea that symptoms are caused by plastic deformation of ligaments.  McPoil should not be considered to have introduced a new theory of biomechanics, but instead to give added definition and clarity to the basic Root principles.

  1. The authors contend that different types of activities require different orthotics with the following argument: “Momentum (mass times velocity) is the third factor that affects the magnitude of the downward force of the body.  Running over a force plate produces more impact force than walking. Therefore, we must consider a range of forces to resist called, ADL or activities of daily living, and calibrate the orthotic to deliver an equal and opposite range.  Athletes may have a different range of forces, these can be referred to as training or competing ranges, which are much higher.  A power lifter, for example, may want an orthotic calibrated to resist his entire weight plus the weight he is deadlifting or squatting.  That same athlete will need a different pair of orthotics for his ADL.”

This paragraph assumes that all ADLs require the same amount of pronation or supination.  If this were true, then the authors’ argument would be correct, however we know that when running, the foot has to pronate more [28].  Therefore to make an orthotic thicker for running, would limit the runner to less than the desired amount of pronation.  The Root orthotic, on the other hand, says that with increasing vertical braking force of the ground, such as what the runner encounters with every foot strike, the orthotic will allow greater amounts of pronation. Just as the Modulus of Elasticity is the same for the foot when it is walking as when it is running (assuming a nonviscoelastic model), so the same orthotic can often be used for many different activities, as it will flex more when running, thus allowing for more pronation, than when walking.

  1. The following statement about practitioner testing the patient is made by the authors: “Foot flexibility can be measured in different ways.  One way to grade foot flexibility is to rotate the forefoot around the fifth metatarsal.  This is called the Gib Test or forefoot flexibility Forefoot Flexibility Test.  The foot can be graded from one to five [20].”

The reference is to the primary author’s own article in a non-refereed magazine article.  Inspection of this article shows nowhere in it is there anything about the Gib Test or the Forefoot Flexibility Test.  A search of the NHI library likewise turns up no article that discusses the Gib Test.  The only place that a practitioner can learn anything about this test is a Youtube video [29].

  1. In regards to some limited research that has been done with the MASS orthotic, the authors state the following:  “Higby measured the force distribution on the metatarsal heads at toe off [23]. What are these forces? Initially, MASS posture orthotics transferred 44% more force to the first metatarsal head at toe off than neutral position orthotics with posts. At six weeks this difference grew to 61% (p=.006) [24]. This means that when the arch is raised, the first ray not only comes down and lateral, but additionally increases its purchase.”

First the editors should have noticed that reference 23 and reference 24 are the same, to a paper by Hodgson, Tis, Cobb, McCarthy and Higbie (not Higby) [30].  So let’s look at the paper quoted by Hodgson.  Glaser and Fleming have totally misrepresented the paper.  The paper looked at two groups, both with greater than 7° forefoot varus.  One was assigned to be treated with a 3/16” polypropylene orthotic manufactured by PAL Labs of Pekin, Ill., and the other by Sole Orthotic Lab.  The “Root” orthotic in this study differed from classic Root techniques in that cast was taken using a prone non-weightbearing casting technique, and the material was more flexible than what Root advocated.

When one looks at the two groups, we see some glaring differences before wearing orthotics.  The “Root” group showed an initial condition in which the first metatarsal head was bearing 71 KPa less pressure than the central metatarsal head area, and the SOLE group had an initial difference of the first metatarsal head having 41 KPa less pressure than the central metatarsal head area.  This is a very significant difference showing that the Root group had significantly more hypermobility of the first ray than the SOLE group.  This is an interesting statistical aberration, where random assignment to two groups does not always produce two groups of equality.

When we look at the end results (6 weeks of wearing the orthotics), the hypermobility of the first ray had not changed with either group.  The first group still shows the first metatarsal head area to be averaging 73 KPa less than the central metatarsal head area, and the second group still shows the first metatarsal head averaging 40 KPa less than the central metatarsal head area.  Therefore the claims by the authors that the SOLE orthotic increased the pressure under the first metatarsal more than the Root orthotic is not an accurate interpretation of the data.

There is an assumption here that the more force one produces under the first metatarsal head, the better the foot is functioning. Actually the Hodgson study is measuring pressure, not force, and in this writer’s eyes, the average pressure under the metatarsal heads over the entire gait cycle should be equal for all five.

Finally the following examples are ways that authors make outlandish assumptions, demonstrate poor reasoning, and write what can be best called “mechano-babble”.

  1. The authors make the following statement: “I propose that the locking mechanism of the midfoot is multifaceted.  When the talar head is directly on top to the anterior facet, sagittal plane motion between the talus and calcaneus is blocked.  Thus, when the gastroc-soleus complex fires, rotation occurs at the ankle joint.”

Not quite sure why the personal pronoun is utilized at the beginning of the article.  Who is the “I”, Dr. Glaser or Dr. Fleming?  This is just one of many editorial errors in the article.  Nevertheless, the assumption that the anterior facet blocks sagittal plane motion between the talus and the calcaneus is faulty reasoning.  First of all, a great many people show the anterior and middle and anterior facet to be one continuous surface [31-33]. The authors fail to mention how the middle facet plays into the equation in blocking subtalar joint motion.  It is well recognized that the middle facet is larger than the anterior facet, so why doesn’t the middle facet block sagittal plane motion, especially since it is further from the subtalar joint axis than the anterior facet?  And what about people with no anterior facet, is there anything blocking subtalar joint motion [34]?

Second of all, the subtalar joint moves around an axis.  It is true that that the facet morphology determines the direction of the subtalar joint axis.  It is important to remember that when we talk about subtalar joint motion being tri-planar, we are not talking about three different motions, we are only saying that angular motion can be measured in three different planes.  Therefore, the more horizontal the facets are with the ground, the greater will be the angular displacement measured in the transverse plane rather than in the sagittal or frontal plane.  In other words, the subtalar joint axis will be more vertical, and therefore the lower will be the torque around subtalar joint axis exerted by vertical ground forces, and the greater will be the torque exerted by shear ground forces.  Since there are strong transverse plane rotational forces occurring in the lower leg during gait, no one can say that a subtalar joint axis that is more vertical will demonstrate less total motion, though a person that has only the capability to measure the frontal plane component of motion may erroneously conclude that less motion may be occurring [35].

Finally, the authors try to confuse the situation with a statement about rotation around the ankle joint occurring when the gastroc-soleus fires.  It is important to remember that when the gastrocnemius-soleus fires, it primarily produces a plantarflexion torque of the calcaneus against the tibia.  Since the ankle joint axis is almost perpendicular to the Achilles tendon, the major torque is around the ankle joint.  The axis of the subtalar joint has a lower angle with the Achilles and a shorter lever arm, therefore the supination torque is lower around the subtalar joint axis than the ankle. The greater the pitch of the subtalar joint axis with the transverse plane, the less will be the torque exerted by the Achilles on the subtalar joint.  Now in closed kinetic chain, when the firing of the gastrocnemius produces a first class lever effect, creating ground reaction force against the metatarsal heads.  This ground reaction force creates a strong dorsiflexion torque around the midtarsal joint.  This dorsiflexion torque is resisted by the ligaments of the plantar foot.  A simple geometrical construct shows that the lower the arch, the greater will be the tension on the plantar ligaments.

  1. The authors make the following statements: “As the foot goes into further elevation of its posture, there is a zone where, according to Hammel, there is no significant rotation around the STJ axis in any plane [17]. Foot orthoses that attempt to elevate posture into this zone often cause medial longitudinal arch pain as the foot repeatedly drops down to impact the orthotic.  Hammel showed that from 25% to 90% of the stance phase of gait, no rotation in any plane occurs between the talus and the calcaneus.”  

First of the use of the paper from Hammel to back up this statement is bogus.  An examination of the paper shows that cadaver feet were utilized to try to simulate gait and the simulator had no transverse plane simulation of the leg.  Without the ability to simulate transverse plane motion of the lower leg, of course they will not be able to pick up the motion of the subtalar joint between 25%-90% of the stance phase of gait. There are many other papers Glaser and Fleming could have picked to discuss the subtalar joint motion that have in vivo multisegment data on all three body planes, including Carson (2001), Hunt (2001), Simon (2006), Stebbins (2006), Leardini (2007), Nester (2007), Pohl (2007), Nester (2014) [36-43].  While all of these authors used slightly different marking systems of the foot when walking, none of them grossly contradicted the original gait cycle motions of the ankle, subtalar or midtarsal joints described by Root and all of these papers, plus many more, contradict the statement of Hammel that Glaser and Fleming rely on.

The statement that subtalar rotation and postural collapse are independent events occurring at different times in the gait cycle is not really a valid statement.  Root stated that subtalar joint pronation occurs before the forefoot hits the ground.  The moment the lateral side of the forefoot touches the ground, the pronation of the midfoot in the sagittal plane starts to occur.  The problem is that the force is transferred gradually to the forefoot from the heel.  Thus the dorsiflexion moment across the midfoot increases throughout the midstance period of gait.  It is the pronation of the subtalar joint that increases the midtarsal joint range of motion in the pronation direction.  Limited data exists in this regard as to the exact mechanism by which the STJ position changes the mobility of the MTJ, and many theories have been proposed [44,45].

At the end of this section in the paper, the readers are still scratching their heads as to what the writers mean by the “Dysfunctional Zone”.  It is even more nebulous and ill-defined than Root’s “neutral position.”

  1. The authors make the following statement: “As foot posture elevates beyond the Dysfunctional Zone the anterior facet of the STJ approaches level in the transverse plane.  This allows subtalar rotation to occur.  This is where the talar head slides posterior and rotates its six degrees around the STJ axis.  The closer the anterior facet is to level, the easier the subtalar rotation occurs and the rearfoot locks in the sagittal plane facilitating efficient propulsion.”

It should be noted that the authors are relying on their own study published in this same edition of the journal on his measurements of facet deviations from each of the planes.  Unfortunately, this paper appears at first to have some real data, however a close read of the paper shows that it is mathematical gibberish.  The quoted article fails to define the reference coordinate system and what directions are positive and negative.  Also the deviation between two planes is determined by the angle between the normals  of the two planes.  If one says that the angle between a facet and the transverse plane is 10°, it could mean that the facet is tilted forward or it could mean that the facet is tilted medially or laterally.  What the author should have done is set up his reference coordinate system and then expressed the normals to the planes of the facets in either spherical or cylindrical terms.  It is noted that most podiatric texts express axes in cylindrical terms.  So with no definitions in the quoted article, the data is useless.

To define the ease of movement on the orientation of one portion of the total joint surfaces that comprise it, and on no ligamentous restraints is totally to ignore mechanics.  As Phillips and Lidtke pointed out, the subtalar joint can be clinically modeled to move around a single axis that is fixed to the talus.  As the talus dorsiflexes in the ankle joint, the subtalar joint becomes more vertical, therefore vertical ground forces produce less torque around the subtalar joint axis and horizontal forces produce more torque.  Therefore transverse plane leg rotations produce stronger subtalar joint torques, and these rotational forces are being generated by the movement of the swing leg.  Also as the talus abducts, the subtalar joint axis moves laterally, producing longer lever arms for the vertical forces medial to the subtalar joint axis and shorter lever arms for the vertical forces under the lateral foot.  So the ease of subtalar joint supination with the foot in a more supinated position can be fully explained without any need for the horizontal position of the anterior facet.

  1. The authors make the following claim: “A MASS Posture composite leaf spring applies an even distribution of force per unit of area by remaining in full contact with the foot throughout the gait cycle.  The foot never has to drop down to hit the orthotic because it is already touching it, which minimizes impact and thus tissue stresses.   It is the combination of full contact  (redistribution of force per unit area) eliminating hot spots and the lack of repetitive impact that allow such a spring to apply a rather large corrective force while remaining comfortable to most patients.  Once you have the correct geometry of the spring, it is time to adjust the spring constant.”

The authors have never demonstrated how their orthotic is constructed like a leaf spring, or why his orthotic is a leaf spring and the Root orthotic is not.  Leaf springs are laminar with the thickest part of the spring in the middle, where the highest load area is.  The MASS theory orthotic is a single lamina and is ground thinner in the middle.

All orthotics remain in full contact with the foot throughout the gait cycle as the foot will mold itself to fit the orthotic shape, which is also a basic tenet of Root orthotic therapy.  A Root orthotic starts pushing against the bottom of the foot when the foot makes contact with it when the STJ is in neutral and the MTJ is pronated.  The more the foot tries to deform from STJ neutral and MTJ pronated, the harder the orthotic pushes against the bottom of the foot.  Blake and Kirby have both proposed modifications of the Root orthotic that initiates the orthotic producing a supinatory force against the heel before the subtalar joint tries to pronate beyond neutral [46-49].

How do the authors know there are no hot spots on the MASS orthotic?  You have to have a pedobarograph to measure that, and there is no literature that has measured the force that the MASS orthotic puts against the bottom of the foot.  This writer’s personal experience with the MASS orthotic is that it produces an extreme hot spot under the medial arch.  If the orthotic is casted with the forefoot maximally plantarflexed against the rearfoot, then there will be a very high hot spot under the arch, unless the orthotic is flexible enough to lower under normal weightbearing to that point where tension develops in the plantar ligaments.  Since there is no quantitative measures taken by the clinician before prescribing a MASS theory orthotic, neither goniometric nor pedobarographic nor kinematic measurements, only a qualitative judgement of the frontal plane mobility of the forefoot to the rearfoot, there is no way that the laboratory has any information about how much the forefoot plantarflexing mobility the patient has.

In conclusion, MASS theory has little to any support for its validity in the literature.  There is only very limited literature on the use of the MASS orthotic.  Currently there is only one source of MASS orthotics, and the authors of the reviewed article have a definite conflict of interest in the proposals offered.  This writer will admit that there are definite problems in the classic “Root” approach that is commonly taught, and many authors since the original Root writings have definitely made valuable additions, clarifications and corrections to the Root approach.  However, this writer, through study of the literature and clinical practice maintains that the literature better supports Root concepts, and therefore MASS theory cannot be accepted as a replacement for currently accepted practices and theories.

Thank you,

Robert D. Phillips, D.P.M.

Orlando Veterans Administration Medical Center

Disclaimer:  the opinions in this paper are those of the writer alone, and do not represent the opinions of the U.S. Department of Veterans Affairs nor any other branch of the U.S. government.

References

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  2. Phillips, R. D., and R. L. Phillips. “Quantitative Analysis of the Locking Position of the Midtarsal Joint.” Journal of the American Podiatric Medical Association 73, no. 10 (1983): 518-522.
  3. McPoil, Thomas G., Harry G. Knecht, and Dale Schuit. “A Survey of Foot Types in Normal Females between the Ages of 18 and 30 Years*.” Journal of Orthopaedic & Sports Physical Therapy 9, no. 12 (1988): 406-409.
  4. Åström, Mats, and Tina Arvidson. “Alignment and Joint Motion in the Normal Foot.” Journal of Orthopaedic & Sports Physical Therapy 22, no. 5 (1995): 216-222.
  5. Lee, William Eric. “Podiatric biomechanics. An Historical Appraisal and Discussion of the Root Model As A Clinical System of Approach in the Present Context of Theoretical Uncertainty.” Clinics in Podiatric Medicine and Surgery 18, no. 4 (2001): 555-684.
  6. Steindler, Arthur. “The Supinatory, Compensatory Torsion of the Fore-Foot in Pes Valgus.” Journal of Bone and Joint Surgery Am 11, no. 2 (1929): 272-276.
  7. Schuster, R. O. “Neutral plantar impression cast: method and rationale.” Journal of the American Podiatry Association 66, no. 6 (1976): 422-426.
  8. Hicks, J. H. “The mechanics of the foot: I. The joints.” Journal of Anatomy 87, no. Pt 4 (1953): 345.
  9. Lundberg, A., and O. K. Svensson. “The axes of rotation of the talocalcaneal and talonavicular joints.” The Foot 3, no. 2 (1993): 65-70.
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  14. Inman, Verne T. “The influence of the foot-ankle complex on the proximal skeletal structures.” Artificial Limbs 13, no. 1 (1969): 59-65.
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  17. Leardini, A., M. G. Benedetti, L. Berti, D. Bettinelli, R. Nativo, and S. Giannini. “Rear-foot, mid-foot and fore-foot motion during the stance phase of gait.” Gait & Posture 25, no. 3 (2007): 453-462.
  18. Lundgren, P., C. Nester, A. Liu, A. Arndt, R. Jones, A. Stacoff, P. Wolf, and A. Lundberg. “Invasive in vivo measurement of rear-, mid-and forefoot motion during walking.” Gait & Posture 28, no. 1 (2008): 93-100.
  19. Nester, Christopher J., Hannah L. Jarvis, Richard K. Jones, Peter D. Bowden, and Anmin Liu. “Movement of the human foot in 100 pain free individuals aged 18-45: implications for understanding normal foot function.” Journal of Foot Ankle Research 7, no. 1 (2014): 51.
  20. Root, Merton L., John H. Weed, and William Phillip Orien. Neutral position casting techniques. Los Angeles, Clinical Biomechanics Corporation, 1971.
  21. Root, M. L. “Development of the Functional Orthosis.” Clinics in Podiatric Medicine and Surgery 11, no. 2 (1994): 183-210.
  22. Phillips, Robert D., and Roy H. Lidtke. “Clinical determination of the linear equation for the subtalar joint axis.” Journal of the American Podiatric Medical Association 82, no. 1 (1992): 1-20.
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  24. McCulloch, Marina U., Denis Brunt, and Darl Vander Linden. “The effect of foot orthotics and gait velocity on lower limb kinematics and temporal events of stance 1.” Journal of Orthopaedic & Sports Physical Therapy 17, no. 1 (1993): 2-10.
  25. Genova, Jean Massé, and Michael T. Gross. “Effect of foot orthotics on calcaneal eversion during standing and treadmill walking for subjects with abnormal pronation.” Journal of Orthopaedic & Sports Physical Therapy 30, no. 11 (2000): 664-675.
  26. Kitaoka, Harold B., Zong-Ping Luo, Hideji Kura, and Kai-Nan An. “Effect of foot orthoses on 3-dimensional kinematics of flatfoot: a cadaveric study.” Archives of Physical Medicine and Rehabilitation 83, no. 6 (2002): 876-879.
  27. Zifchock, Rebecca Avrin, and Irene Davis. “A comparison of semi-custom and custom foot orthotic devices in high-and low-arched individuals during walking.” Clinical Biomechanics 23, no. 10 (2008): 1287-1293.
  28. Rodgers, Mary M. “Dynamic biomechanics of the normal foot and ankle during walking and running.” Physical therapy 68, no. 12 (1988): 1822-1830.
  29. https://www.youtube.com/watch?v=OapU4rr2WUM&index=2&list=PL3DF1D76572D6C26A
  30. Hodgson, Brad, Laurie Tis, Steven Cobb, Shawn McCarthy, and Elizabeth Higbie. “The effect of 2 different custom-molded corrective orthotics on plantar pressure.” Journal of Sport Rehabilitation 15, no. 1 (2006): 33-44.
  31. Bunning, P. S. C., and C. H. Barnett. “A comparison of adult and foetal talocalcaneal articulations.” Journal of Anatomy 99, no. Pt 1 (1965): 71.
  32. Bruckner, Jan. “Variations in the human subtalar joint.” Journal of Orthopaedic & Sports Physical Therapy 8, no. 10 (1987): 489-494.
  33. Uygur, Mujde, Funda Atamaz, Servet Celik, and Yelda Pinar. “The types of talar articular facets and morphometric measurements of the human calcaneus bone on Turkish race.” Archives of Orthopaedic and Trauma Surgery 129, no. 7 (2009): 909-914.
  34. Ragab, Ashraf A., Susan L. Stewart, and Daniel R. Cooperman. “Implications of subtalar joint anatomic variation in calcaneal lengthening osteotomy.” Journal of Pediatric Orthopaedics 23, no. 1 (2003): 79-83.
  35. Phillips, R. D., R. Christeck, and R. L. Phillips. “Clinical measurement of the axis of the subtalar joint.” Journal of the American Podiatric Medical Association 75, no. 3 (1985): 119-131.
  36. Carson, M. C., M. E. Harrington, N. Thompson, J. J. O’connor, and T. N. Theologis. “Kinematic analysis of a multi-segment foot model for research and clinical applications: a repeatability analysis.” Journal of Biomechanics 34, no. 10 (2001): 1299-1307.
  37. Hunt, Adrienne E., Richard M. Smith, Marg Torode, and Anne-Maree Keenan. “Inter-segment foot motion and ground reaction forces over the stance phase of walking.” Clinical Biomechanics 16, no. 7 (2001): 592-600.
  38. Simon, J., L. Doederlein, A. S. McIntosh, D. Metaxiotis, H. G. Bock, and S. I. Wolf. “The Heidelberg foot measurement method: development, description and assessment.” Gait & Posture 23, no. 4 (2006): 411-424.
  39. Stebbins, J., M. Harrington, N. Thompson, A. Zavatsky, and T. Theologis. “Repeatability of a model for measuring multi-segment foot kinematics in children.” Gait & Posture 23, no. 4 (2006): 401-410.
  40. Leardini, A., M. G. Benedetti, L. Berti, D. Bettinelli, R. Nativo, and S. Giannini. “Rear-foot, mid-foot and fore-foot motion during the stance phase of gait.” Gait & Posture 25, no. 3 (2007): 453-462.
  41. Nester, C., Richard K. Jones, A. Liu, David Howard, A. Lundberg, A. Arndt, P. Lundgren, A. Stacoff, and P. Wolf. “Foot kinematics during walking measured using bone and surface mounted markers.” Journal of Biomechanics 40, no. 15 (2007): 3412-3423.
  42. Pohl, Michael B., Neil Messenger, and John G. Buckley. “Forefoot, rearfoot and shank coupling: effect of variations in speed and mode of gait.” Gait & Posture 25, no. 2 (2007): 295-302.
  43. Nester, Christopher J., Hannah L. Jarvis, Richard K. Jones, Peter D. Bowden, and Anmin Liu. “Movement of the human foot in 100 pain free individuals aged 18-45: implications for understanding normal foot function.” Journal of Foot and Ankle Research 7, no. 1 (2014): 51-60
  44. Kitaoka, Harold B., Tae-Kun Ahn, Zong Ping Luo, and Kai-Nan An. “Stability of the arch of the foot.” Foot & ankle international 18, no. 10 (1997): 644-648.
  45. Blackwood, C. Brian, Tracy J. Yuen, Bruce J. Sangeorzan, and William R. Ledoux. “The midtarsal joint locking mechanism.” Foot & ankle international 26, no. 12 (2005): 1074-1080.
  46. Blake, Richard L. “Inverted functional orthosis.” Journal of the American Podiatric Medical Association 76, no. 5 (1986): 275-276.
  47. Kirby, Kevin A. “The medial heel skive technique. Improving pronation control in foot orthosis”. Journal of the American Podiatric Medical Association 82 (1992): 177-188.
  48. Williams, Dorsey S., Irene McClay Davis and Stephen P. Baitch. “Effect of inverted orthoses on lower-extremity mechanics in runners.” Medicine & Science in Sports & Exercise 195, no. 9131/03 (2003): 2060-2068.
  49. Bonanno, Daniel R., Cheryl Y. Zhang, Rose C. Farrugia, Matthew G. Bull, Anita M. Raspovic, Adam R. Bird, and Karl B. Landorf. “The effect of different depths of medial heel skive on plantar pressures.” Journal of Foot and Ankle Research 5, no. 1 (2012): 1-10.

 

September 2016


9 (3), 2016


Persistent distal sciatic neuropathy following popliteal nerve block in foot and ankle surgery
by Spencer J. Monaco DPM, Alissa Toth DPM, Dane K. Wukich MD


Posterior dislocation of the subtalar joint: A case report
by Vijay Kumar Kulambi, MBBS, MS (ORTHO), Deepak. A, MBBS, (D. ORTHO)


Application of the distally pedicled peroneus brevis: Technique, case study, and pearls
by Chad Seidenstricker DPM, Megan L. Wilder DPM, Byron L. Hutchinson DPM, FACFAS


Fibromatosis of the soleus muscle presenting as pes equinus: A case report
by Hirofumi Bekki MD, Jun-ichi Fukushi MD PhD, Hideki Mizu-uchi MD PhD, Makoto Endo MD PhD, Yoshinao Oda MD PhD, Yukihide Iwamoto MD PhD


Differences in the degree of stretching applied to Achilles tendon fibers when the calcaneus is pronated or supinated
by Mutsuaki Edama, Masayoshi Kubo, Hideaki Onishi, Tomoya Takabayashi, Takuma Inai, Hiroshi Watanabe, Satoshi Nashimoto, Ikuo Kageyama


The application of generic CAD/CAM systems for the design and manufacture of foot orthoses
by Alfred Gatt PhD, Cynthia Formosa PhD, Nachiappan Chockalingam PhD


Prematurely symptomatic tarsal coalition with peroneal spasm in a 2-year-old
by Robert L. van Brederode, DPM, FACFAS


Neglected Achilles tendon rupture and repair with cadaver allograft, extracellular matrix, and platelet enriched plasma
by Al Kline, DPM


Prospective study of plantar fascia thickness correlated to efficacy of conservative treatment for plantar fasciitis using ultrasonography
by Gerald Kuwada, DPM, NMD


Letter to the Editor
by Robert D. Phillips, DPM


Posterior dislocation of the subtalar joint: A case report

by Vijay Kumar Kulambi, MBBS, MS (ORTHO)1, Deepak. A, MBBS, (D. ORTHO)2*pdflrg

The Foot and Ankle Online Journal 9 (3): 2

Dislocation of the talocalcaneonavicular or subtalar joint is a rare occurrence. Posterior subtalar dislocations are even rarer among subtalar dislocations. The injury is characterized by a simultaneous dislocation of talocalcaneal and talonavicular joints while tibiotalar and calcaneocuboid articulations remain intact. Although many of these dislocations result from a high-energy injury, such as a fall from a height or RTA, a significant number of these injuries occur as a result of athletic injuries. Closed reduction and immobilization remains the treatment of choice. Early anatomical reduction is the key to preventing long term complications such as midtarsal joint arthritis and faulty foot mechanics.  However, if closed reduction is unsuccessful in some patients, open reduction is required. A variety of bone and soft tissue structures may become entrapped, resulting in obstruction of closed reduction. This is a unique case report which presents an unsuccessful closed reduction of a closed posterior subtalar dislocation that required open reduction.

Key words: subtalar joint dislocation, foot trauma, STJ, joint dislocation

ISSN 1941-6806
doi: 10.3827/faoj.2016.0903.0002

1 – Professor of Department of Orthopaedics. JJM Medical College, Davangere, Karnataka State, India 577004.
2 – Postgraduate student, Dept. of Orthopaedics, J.J.M. Medical College, Davangere, Karnataka State, India 577004.
* – Corresponding author: deepus_7891@yahoo.co.in / deepus.7891@gmail.com


Subtalar joint (STJ) dislocation is a rare injury of the foot and ankle with most reported cases occurring after major trauma. The rarity of this injury can be attributed to the presence of strong ligament connecting the talus and the calcaneus, the strong biomechanical properties of the ankle and the tight joint capsule. When a dislocation occurs to this joint, it is considered a serious injury due to the instability that can occur across Chopart’s joint [1].

Main and Jowett described this dislocation type injury occurring at the midtarsal joints with a classification system to help the physician decide the best course of treatment (Table 1) [2].

The dislocation results in substantial distortion of the foot shape. Fractures of the fifth metatarsal, the talus, anterior process of calcaneus and the malleoli are often a result of with subtalar dislocations [3]. Subtalar dislocations without associated fracture are rare because of the inherent instability of these types of injuries (the talus has two articular surfaces which contribute in the formation of talonavicular and talocalcaneal joints) [4].

It has also been demonstrated that injury in this area can easily dislocate the subtalar joint. In most of the cases the calcaneus and the rest foot is dislocated medially. Dislocation can be reduced spontaneously [5].

The purpose of this study is to report a rare case of a posterior subtalar dislocation with associated fractures in which closed reduction failed, and ultimately open reduction and internal fixation was done. We also describe the mechanical patterns resulting in subtalar dislocation, s-pitfalls that arise during closed reduction, choosing the right patient for open reduction.

Case Report

A 48 years old male presented with a history of one day old injury to right ankle following an accidental fall by slipping on a slope, with the right foot being forced mainly into hyperplantar flexion and eversion. He presented with complaints of pain, swelling, deformity just distal to the ankle and proximal foot, and was unable to bear weight on right foot.

Table 1 Main and Jowett classification for midtarsal joint injuries [2].

Clinical examination showed the foot being fixed in plantar flexion, mild eversion with diffuse swelling and tenderness in midfoot and proximal 3rd shaft of right fibula region without any type of external wound. A prominent rounded bony prominence was palpated at the talonavicular articulation, suggestive of talonavicular dislocation with palpable talar head. Skin over the dorsum was stretched and edematous. All movement (passive and active) of the right ankle was painful and restricted completely. There was no distal neurovascular deficit. The plain radiographs of right ankle and right leg in AP and lateral views showed posterior talonavicular dislocation with a very mild lateral displacement in the right foot with fracture of anterior process of the right calcaneum and plain radiographs of leg showed fracture of proximal 1/3rd shaft of right fibula (Figures 1 and 2). Initial closed reduction under spinal anaesthesia failed and thus resulting in open reduction with a dorsolateral approach. The talus was explored through a dorsolateral incision and the tendon of tibialis anterior was found to be interposed between the talus and calcaneus. The head of the talus was impacted onto the navicular bone, hindering the attempt for closed reduction.  Tibialis anterior tendon was retracted and talar head had to be levered back into anatomical position after opening the talonavicular joint capsule (Figure 3). The reduction was confirmed under C – arm (Figure 4) and then a thick Kirschner wire was inserted from the calcaneus into the talus to hold the reduction (Figure 5). A below knee splint was applied after placing a sterile dressing at the operative site.

Figure 1 Subtalar dislocation, fibula fracture.

Figure 2 Preoperative x- rays of the patient injured foot.

    

Figure 3 Intraoperative pictures from left to right;  i) tibialis anterior tendon interposing between the talar head; ii) tendon retracted and joint capsule opened exposing the talar head; iii) talar being lever back into anatomical position; iv) post reduction of subtalar joint; v) K – wire fixation post reduction of subtalar joint.

 

Figure 4 Intraoperative images showing talonavicular joint i) pre reduction, ii) post reduction.

 

Figure 5 Intraoperative images showing stabilisation of the talonavicular joint using K-wires.

Discussion
Subtalar joint dislocations were first described in 1811 and have also be referred to as peritalar or subastragalar [6,7]. A more accurate term for subtalar joint dislocations would be talocalcaneal navicular (TCN) dislocations.

The most widely used classification has been described by Broca in 1852 [5], who distinguished 3 types of subtalar dislocation (Table 2): (1) the medial dislocation; (2) the lateral; and (3) the posterior dislocation. Direction of the rest foot in relation to the talus was the determinant element to classify dislocation as medial, lateral or posterior [5]. Subtalar dislocations are rare accounting for approximately 1% of all dislocations; 85% are medial dislocations with the other 15% accounting for lateral and the very rare anterior and posterior dislocations [9].
The incidence of posterior dislocation which was first described by Luxembourg in 1907 and it ranges from 0.8% to 2.5% of all TCN dislocations in different studies [3,4]. Posterior dislocation occurs when forces applied on the dorsum of the foot result in forceful extreme plantar flexion of the forefoot. It is hypothesized that pure hyperplantar flexion could lead to a progressive subtalar ligament weakening that may result in a complete ligament rupture if the plantar flexion force is prolonged [3]. This excessive hyperplantar flexion is normally the result of either a fall from a height or direct blunt force and trauma.

Direction of Dislocation Frequency of Dislocation
Medial 65-80%
Lateral 15-35%
Posterior 0.8-2.5%
Anterior 1%

Table 2 Broca and Malgaigne’s classification of talocalcaneal navicular joint dislocation with frequency [16].

This could be observed in the presence of good bone quality and if the force is applied distally at the navicular bone. The interosseous ligament and medial and lateral ligaments of the ankle joint are torn [9]. Generally there is no rotational component to posterior displacements of the TCN joint. The instances of posterior dislocations with rotational components were open injuries [10].

The diagnosis of posterior TCN dislocation can be confirmed with lateral and anteroposterior radiographs (Figure 3). On lateral radiographs, the head of the talus is atop the navicular, and the posterior portion of the talus will be in contact with the posterior subtalar facet of the calcaneus [11]. According to Inokuchi et al, the frontal view should show no significant medial-lateral displacement or rotation of the foot [3].

Immediate reduction under general or spinal anesthesia is recommended to avoid soft tissue complications and reduce the chances of avascular necrosis of the talus. Posterior dislocations are also very unstable due to the fact that the talus is balancing on two points, the navicular and the facets of the calcaneus, respectively. With posterior TCN dislocation, reduction can be achieved with no fixation by manual traction [9]. A radiograph should be performed to ensure the reduction of the dislocation and to exclude any iatrogenic fracture.

Associated fractures as cited in the literature include, talar neck and body fractures, anterior process of the calcaneus, posterior process of the talus, posterior malleolus chip fractures of the navicular, cuboid fractures, and associated osteochondral fractures [3,4,10,12]. A recent case report by Budd et al, showed that a posterior displacement was irreducible due to an anterior process fragment [12].

In general posterior dislocations do not require internal or external fixation. Fixation of associated fractures is required depending on the type of fracture, displacement, and timing of the injury. In general posterior dislocations do not require internal or external fixation. Fixation of associated fractures is required depending on the type of fracture, displacement, and timing of the injury. Good functional outcomes for closed posterior TCN dislocation have been uniformly reported in the literature [3]. Post-reduction immobilization in a non-weight bearing cast is required for TCN dislocation. In general we follow the protocol set forth by Jungbluth et al in 2010, consisting of six weeks in a short-leg cast with aggressive rehabilitation and full weight bearing thereafter [12]. Radiographs at 6-8 weeks are a usual protocol to ensure no vascular necrosis of the talus. This can also be done with the use of CT and MRI.

Most commonly, subtalar dislocation is an injury resulting from high energy trauma and, more frequently, it involves active young men. Between 10% and 40% of subtalar dislocations are open [7]. Open injuries tend to occur more commonly with the lateral subtalar dislocation pattern and probably as the result of a more violent injury. Long term follow – up demonstrated very poor results with open subtalar dislocation [7].

The duration of immobilization remains controversial. Lasanianos et al [13] suggested that for uncomplicated medial subtalar dislocations, if passive and active range of motion exercises and partial weight bearing are started earlier, the outcomes regarding functionality are better when compared to those of longer immobilization periods [14].
In our case presentation, the patient had sustained a high-energy trauma leading to a posterior subtalar dislocation. Following the initial failed closed reduction attempt under spinal anaesthesia and hence open reduction was required. We identified the tibialis anterior tendon and the impaction of the talar head on the navicular bone obstructing the possible closed reduction. This case report shows successful open reduction of a posterior subtalar dislocation with Kirschner wire fixation.

References

  1. Powell E, LaBella M. Swivel-type Dislocation of the Talonavicular Joint: A case report. The Foot and Ankle Online Journal 2011:4(6):3
  2. Main BJ, Jowett RL. Injuries of the midtarsal joint. JBJS 1975 57B: 89-97
  3. Inokuchi S, Hashimoto T, Usami N. Posterior subtalar dislocation. J Trauma 1997; 42: 310-313
  4. Krishnan KM, Sinha AK. True posterior dislocation of subtalar joint: a case report. J Foot Ankle Surg 2003; 42: 363-365
  5. Zimmer TJ, Johnson KA. Subtalar dislocations. Clin Orthop Relat Res 1989; (238): 190-194
  6. Delee JC, Curtis R. Subtalar dislocation of the foot. J Bone Joint Surg Am 1982;64:433-7
  7. Goldner JL, Poletti SC, Gates HS, et al. Severe open subtalar dislocations. J Bone Joint Surg Am 1995;77-:1075-9
  8. Perugia D, Basile A, Massoni C, Gumina S, Rossi F, Ferretti A. Conservative treatment of subtalar dislocations. Int Orthop 2002;26(1):56-60.
  9. William Yoder, DPM, Patrick Nelson, DPM, Michael Bowen, DPM, Stephen Frania, DPM. Talocalcaneal navicular Dislocation: A review.
  10. Camarda L, Martorana U, D-Arienzo M. Posterior subtalar dislocation. Orthopedics: Case Report. July 2009;32.
  11. Pua U. Subtalar dislocation: rare and often forgotten. In J Emerg Med 2009;2:51-2.
  12. Jungbluth P, Wild M, Hakimi M, et al. Isolated subtalar dislocation. J Bone Joint Surg 2010;92:890-4.
  13. Lasanianos NG, Lyras DN, Mouzopoulos G, Tsutseos N, Garnavos C. Early mobilization after uncomplicated medial subtalar dislocation provides successful functional results. J Orthop Traumatol 2011; 12:37-43
  14. Giannoulis D, Papadopoulos DV, Lykissas MG, Koulouvaris P, Gkiatas I, Mavrodontidis A. Subtalar dislocation without associated fractures: Case report and review of literature. World J Orthop. 2015;6(3):374-9.

 

Persistent distal sciatic neuropathy following popliteal nerve block in foot and ankle surgery

by Spencer J. Monaco DPM1, Alissa Toth DPM2, Dane K. Wukich MD3pdflrg

The Foot and Ankle Online Journal 9 (3): 1

Popliteal nerve blocks are becoming more popular in patients undergoing foot and ankle surgery. The procedure potentially carries fewer complications and is frequently successful while allowing for earlier mobilization when compared with spinal or epidural anesthesia. Reported complications include paresthesias, pain during needle entry and blood aspiration without risk of dural injury or post procedure headache. We present two patients who underwent a popliteal nerve block for a foot and ankle surgery who developed mixed sensory and motor neuropathy that did not fully resolve within their follow up period.

Key words: popliteal nerve block, foot and ankle surgery, sciatic nerve

ISSN 1941-6806
doi: 10.3827/faoj.2016.0903.0001

1,2 – Resident Physician, University of Pittsburgh Medical Center, Podiatric Residency Program, Pittsburgh PA
3 – Professor of Orthopaedic Surgery, Division of Foot and Ankle Surgery, Pittsburgh PA
* – Corresponding author: monacosj2@upmc.edu


Operative and postoperative analgesia has been provided in varying forms which include general anesthesia, spinal or epidural anesthesia, local anesthesia with IV sedation, and peripheral nerve block [1]. Popliteal nerve blocks are becoming more popular in patients undergoing foot and ankle surgery, allowing for earlier mobilization compared with spinal or epidural anesthesia. As a matter of fact, they are being increasingly performed by foot and ankle surgeons rather than by an anesthesia service [5]. The popliteal nerve block was first described by Gaston Labat in 1922 and can be administered from a posterior or lateral approach, with or without the assistance of ultrasound or nerve stimulation. It is believed that the anesthetic interferes with the sodium and potassium channels thus interfering with the action potential [1].

Borgeat et al retrospectively evaluated 1001 patients and reported on complications such as paresthesias, pain during anesthetic administration and blood aspiration [2]. They concluded the procedure is frequently successful and causes few complications.

In 2014, a study reviewing 143 popliteal blocks performed by podiatric surgical residents showed no postoperative complications but an overall success rate of only 76.2% [5]. The purpose of this paper is to present two patients who developed persistent mixed sensory and motor neuropathic syndromes from a popliteal nerve block following a foot and ankle surgical procedure that were still present at final follow up.

Case 1

A 46 year old female presented to our foot and ankle clinic in regards to a right foot drop. She underwent a peroneal tendon repair 8 months prior at an outside facility. She was able to walk with a limp before her surgery however, is now unable to put her foot flat on the ground. During her procedure a calf tourniquet was used for 30 minutes at a setting of 350 mmHg. She received a popliteal nerve block without the use of ultrasound or nerve stimulation. The patient reported the block did not work and she was able to feel her leg and foot before surgery.

1

Figure 1 Clinical photograph of 25 degrees plantarflexion.

Upon presentation to our clinic, she complained of paresthesias including tingling in her entire foot and numbness in the S1 nerve distribution. She tried multiple custom made ankle and foot orthotics with no relief.  She has past medical history of psoriatic arthritis. Past surgical history includes right finger soft tissue mass excision and hysterectomy. Medications include meloxicam and gabapentin.

Physical examination revealed an alert and oriented female with a BMI of 25. Overall her pain was 6 out of 10. She had palpable pedal pulses. Light touch and vibratory sensation were intact. Achilles and patellar deep tendon reflexes were also intact. Her ankle was fixed at 25 degrees of plantarflexion which was non-reducible and did not improve with knee flexion (Figures 1 and 2). Manual muscle testing demonstrated 3/5 inversion and eversion, 4/5 digital plantarflexion and dorsiflexion and 3/5 ankle dorsiflexion.  Mid-calf circumference was six centimeters less than the non-affected side. Electromyography (EMG) and nerve conduction velocity (NCV) studies showed acute axonal degeneration in muscles innervated by the tibial, superficial peroneal, lateral plantar and deep peroneal nerves consistent with a distal sciatic neuropathy.  A 3T MRI scan was completed which showed signal intensity of the posterior tibial muscle and soleus muscles indicating atrophy. She underwent a Z lengthening of the triceps surae and posterior ankle joint capsule release to correct the equinus deformity (Figure 3). At 4-month follow up, the patient’s foot remained at 90 degrees relative to the leg, however, had continued neuropathic symptoms. She was referred to peripheral nerve surgery for possible neurolysis and nerve grafting.

2

Figure 2 Clinical photograph illustrating equinus deformity during weightbearing.

3

Figure 3 Intraoperative photograph of Z lengthening with posterior ankle joint capsule release.

Case 2

A 17-year-old male sustained a 5th metatarsal zone 2 injury of his right foot and was treated with percutaneous intramedullary screw fixation. He received a preoperative regional nerve block by the anesthesia service. Ultrasound or nerve stimulation was also not used.  During his procedure a calf tourniquet was used for 45 minutes at 250 mmHg. During his postoperative course, he developed ipsilateral calf and intrinsic foot muscle atrophy along with pain he described as “pins and needles.” He had an unremarkable past medical history. He had no other past surgical history.

The patient’s BMI was 26.9. Physical examination revealed impaired sensation in the peroneal and tibial nerve distributions at the pedal level. Strength testing revealed 4/5 strength of the tibialis anterior and gastrocnemius muscles. Extensor hallucis longus was 4/5 with full strength to hamstrings, quadriceps, and adductors. EMG/NCV studies showed chronic right sciatic neuropathy distal to the biceps femoris and semimembranosus muscles at 12 months following surgery as well as severe axon loss to intrinsic foot muscles. He was referred to physical medicine and rehabilitation. He was recommended custom orthotics and exercises as well as a home transcutaneous electrical nerve stimulation unit. He was also given B12 vitamin complex and fish oil. His symptoms improved with the exception of intrinsic muscle function and tone, which was persistent at 2 year follow up.

Discussion

Motor and/or sensory neuropathy from a popliteal nerve block is uncommon for patients undergoing foot and ankle surgery with reported incidence of between 1.26% and 5% [1-2]. In a recent retrospective study of 1014 patients who had a popliteal block for foot and/or ankle surgery, the overall success rate was 97.3%. 135 patients reported varying manifestations of neuropathic complications.  Eight of these patients retrospectively reviewed developed exclusively motor deficits, 118 exclusively sensory deficits and the remaining nine patients reported mixed sensory and motor deficits.

At final follow up, 14 patients had residual neuropathic symptoms. No statistical significance was found between tobacco use, diabetes, tourniquet location or time, block procedure techniques, single or continuous blocks, or ultrasound or nerve stimulation [1].

A retrospective study of popliteal nerve blocks for hallux valgus surgery showed an incidence of 1.91% for 157 consecutive hallux valgus surgeries. 44% of the blocks were performed with ultrasound in conjunction with nerve stimulation [4].

In 2012, Gartke et al prospectively studied the effects of continuous rather than single shot popliteal blocks in foot and ankle surgery [3]. The study showed a 41% incidence at 2 weeks that decreased to 24% at 8 months. In this study, only 4% of the patients manifested symptoms to warrant referral to a neurologist or pain specialist.  

Although regional nerve blocks prior to foot and ankle surgery are generally effective and obviate the negative side effects of opioids or other sedation, careful patient counseling should be planned prior to the procedure. Continuous popliteal nerve blocks may have a higher incidence of transient postprocedural neuropathy versus single shot blocks. Although the majority of neuropathies are isolated sensory deficits that resolve in a period of months, we present two cases of mixed sensorimotor deficits that persisted beyond final follow up. Interesting, both patients that developed distal sciatic neuropathy did not have guidance from either an ultrasound or nerve stimulator during the nerve block. Moving forward, all patients at our institution undergoing a popliteal nerve block have either ultrasound guidance and/or nerve stimulation which is performed by the anesthesia service.

References

  1. Anderson JG, Bohay DR, Maskill JD, et al. Complications After Popliteal Block for Foot and Ankle Surgery. Foot Ankle Int. 2015;36(10):1138-43.
  2. Borgeat A, Blumenthal S, Lambert M, Theodorou P, Vienne P. The feasibility and complications of the continuous popliteal nerve block: a 1001-case survey. Anesth Analg. 2006;103(1):229-33.
  3. Gartke K, Portner O, Taljaard M. Neuropathic symptoms following continuous popliteal block after foot and ankle surgery. Foot Ankle Int. 2012;33(4):267-74.
  4. Hajek V, Dussart C, Klack F, et al. Neuropathic complications after 157 procedures of continuous popliteal nerve block for hallux valgus surgery. A retrospective study. Orthop Traumatol Surg Res. 2012;98(3):327-33.
  5. Hegewald K, McCann K, Elizaga A, Hutchinson BL. Popliteal blocks for foot and ankle surgery: success rate and contributing factors. J Foot Ankle Surg. 2014;53(2):176-8.

 

 

 

 

 

 

June 2016

9 (2), 2016


Modified Scarf osteotomy for treatment of hallux valgus
by Saad R. El Ashry, M. S. Sidhu, Abhay Tillu


Lisfranc-like injury involving lateral tarsometatarsal joints: a case report
by Mir Tariq Altaf, Muhammad Haseeb, Varun Narula, Aakash Pandita


Postoperative analgesic efficacy of dexamethasone sodium phosphate versus triamcinolone acetonide in bunionectomy: A prospective, single-blinded pilot randomized controlled trial
by Chris Olivia Ongzalima, Wei Lin Renee Lee, Anh Hoang, Ming Yi Wong, Reza Naraghi


Does shoe midsole temperature affect patellofemoral and Achilles tendon kinetics during running?
by Sinclair J, Atkins S, Shore H


Form determines function: Forgotten application to the human foot?
by Mick Wilkinson, PhD and Lee Saxby, BSc


Lateral and open medial subtalar dislocation: Report of two uncommon cases
by Ganesh Singh Dharmshaktu, Irfan Khan


Steroid intra-articular injections for foot and ankle conditions: How effective are they?
by Mohammed KM Ali, Suhayl Tafazal, CA Mbah, D Sunderamoorthy


Effects of energy boost and springblade footwear on knee and ankle loads in recreational runners
by Jonathan Sinclair


Longitudinal Arch Angle (LAA): Inter-rater reliability comparing Relaxed Calcaneal Stance with Toe Off
by Edward S. Glaser DPM, Stephen Goodman MS, David Fleming BS, Misty Shelby cPed, Raymond Lovato cPed, Eric Tidwell cPed


Longitudinal Arch Angle (LAA): Inter-rater reliability comparing Relaxed Calcaneal Stance with Toe Off

by Edward S. Glaser DPM1, Stephen Goodman MS2, David Fleming BS2*, Misty Shelby cPed2, Raymond Lovato cPed2, Eric Tidwell cPed2pdflrg

The Foot and Ankle Online Journal 9 (2): 9

Purpose:  The purpose of this study is to determine the inter-rater reliability of the LAA taken at the bottom of the foot’s postural range of motion RCSP(Relaxed Calcaneal Stance Posture) as compared with the LAA when the foot is in a toe off posture at forty degrees of heel elevation.
Design:   An investigation into a new technique for capturing Longitudinal Arch Angle in patients.
Samples:  Subjects submitted voluntarily from a heterogeneous sampling of factory workers in rural Tennessee.
Methods:  LAA captured in RCSP and toe off posture using the iOS LAAngle™ App
Main Outcome Measures:  We measured the LAA of 85 sets of feet with the iOS App to obtain the LAA in RCSP and Toe off conditions.
Results:  The IntraClass  Correlation Coefficient (2,1) was 0.7 for RCSP and Toe off.  This was across an age range of 17 to 68 years with 50 male and 35 female subjects.
Conclusions: The  iOS LAAngle™ App is an efficient and reliable method for calculating a patient’s LAA.
Key words: Longitudinal Arch Angle, Foot Posture, MASS Posture,  biomechanics

ISSN 1941-6806
doi: 10.3827/faoj.2016.0902.0009

1 – Founder and CEO of  Sole Supports, Inc.
2 – Sole Supports, Inc.
* Corresponding author: dfleming@solesupports.com


The measurements of static foot positions and motions recommended by Root, Orien and Weed in the static biomechanical examination [1] have been brought into question by several authors. Van Gehluwe et al showed that the inter rater reliability of these measurements was poor [2]. Fifteen of the seventeen measurements demonstrated an inter rater reliability of 0.5 and the remaining two had 0.6 which was still insignificantly clinically.

Additionally McPoil et al studied the relationship of the static biomechanical examination values in relation to calcaneal eversion angles taken in gait as measured with a motion analysis system and found that the values measured in the static biomechanical examination proposed by Root et al did not correlate with dynamic foot function [3]. Measurements of Radiographs have also been used to evaluate the foot biomechanically but these images are taken with the foot in angle and base of gait with the foot in its relaxed calcaneal stance posture [4]. They therefore may give the clinician information on the extent of over pronation that is possible when the foot fully collapses but tell us nothing about the corrected posture.

They do have some value in determining pre-operative collapse as compared to post-operative correction but fail to give any information regarding the extent of correction that is either possible or ideal. We were unable to find a study that supports a test that gives the clinician any information as to how much postural correction is possible with a custom molded prescription foot orthotic.

Donatelli proposed a measurement of the angle between the medial malleolus, the navicular tubercle, and the medial aspect of the first MTP joint [5].  Jonson et al studied a similar angle in young healthy Navy subjects.  In this study, dots were made on the center of the medial malleolus, medial prominence of the navicular bone and medial head of the first metatarsal head.  The angle was measured manually with a goniometer with the patient in the relaxed calcaneal stance posture.  Again, the bottom of the postural range of motion of the foot, was tested giving the clinician no indication as to how much postural correction is possible.  They demonstrated a high inter and intra-rater reliability (0.81) and the test yielded almost identical results of both right and left feet.  Although, they stated their sampling was of relatively lean and physically fit young males with easy to identify boney prominences, subjects from a specific geographical region [6].

McPoil and Cornwell did further testing to determine the correlation of this angle between static stance and walking [7], and showed that the relaxed calcaneal stance posture LAA correlated 90% to the same angle measured at the lowest posture achieved during walking.  McPoil and Cornwell went on to compare this fully collapsed LAA between standing and running and found approximately an 85% correlation[8].  The LAA was further studied by Heidi Burn et al who concluded that the “LAA is been shown to be a good static measure for dynamic foot function and can reliably be implemented in a normal clinical environment to evaluate and assess the efficacy of the prescribed foot orthoses” [9]. Again, the LAA was only tested in its fully pronated or maximally collapsed posture.

We propose an exact protocol for measurement and introduce an iOS App to measure the LAA that may improve the accuracy of this test.  Additionally, the LAA is measured in two different postures.  The relaxed calcaneal stance posture LAA is compared to the LAA when measured at 40 degrees of rear foot elevation.  This angle was selected because it closely approximates MASS posture, as defined by Glaser et al as the Maximal Arch Supination Stabilization Posture which is the most elevated posture the foot can attain at midstance with the heel and forefoot in full contact with the supporting surface with the soft tissues evenly compressed.  Glaser proposes this posture as a corrective geometry for a calibrated leaf spring to apply an equal and opposite range of forces to those imposed by the body during the gait cycle.  Glaser has theorized that this shape leaf spring may assist the foot in resisting the repetitive downward forces of walking and aid the foot in achieving a more functional posture for propulsion and thereby alleviate many foot symptoms and possibly reverse some deformity of the foot as well as improve the passage of center of pressure through the foot during gait.

Higbie et al demonstrated that foot orthotics made in MASS posture initially transferred 44% more force to the first metatarsal head at toe off than any orthotic previously tested at Georgia State University and at 6 weeks the improvement over previous technologies measured 61% [10].  Cobb et al demonstrated a significant improvement in postural sway (movement of the body’s center of gravity from right to left) in patients with greater than 7 degrees of forefoot varus [11].  Piernowski and Trotter tested the inter and intra-rater reliability of the casting with Canadian cPeds.  They found intra-rater reliability to be significantly improved with MASS Posture casting technique [12].  Piernowski and Trotter also tested the Biomechanical Efficiency Quotient(BEQ) on patients wearing MASS posture orthotics and found significant improvements in BEQ using MASS Posture [13] which correlated to patient outcomes in a separate paper [14].  Garbalosa et al showed that foot orthoses that incorporate total contact and direct support of the medial longitudinal arch are clinically significant in their effect on the kinematics of the foot as well as their ability to reduce painful symptoms of the lower extremity [15].

Materials and Methods

Eighty-Five subjects were selected for the study.  Due to the non-invasive nature of the measurements taken no Human Subjects committee approval was deemed necessary but each patient did sign an informed consent form.  Subjects did not receive payment for their participation.   Patients with previous surgical correction were eliminated.  There was 85 subjects total, 50 were male and 35 female and ranged in age from 17 to 68 years with a mean age of 40.7 years.  Three certified pedorthists performed the testing.  A pilot study was performed to determine the protocol.  The testers and authors met to approve final protocol.  An App was written to capture the LAA in real time with automatic capture at the lowest posture of the foot:  Relaxed calcaneal stance posture and the posture the foot will attain at a 40 degree angle between the plane of the plantar aspect of the foot and the ground.  The following protocol for capturing the LAA was used in this experiment:

Figure 1

Figure 1  iOS scanning setup with green adhesive dots placed on key areas. Subjects foot placed in Relaxed Calcaneal Stance Position.

Figure 2

Figure 2  “Mask” mode of LAAngle™ App to set contrast.

  • Green adhesive dots were placed on the center of the medial malleolus and center of the navicular tuberosity off weight bearing.  
  • The patient places the foot on the ground in heel to toe fashion.
  • Dots on the medial aspect of the first metatarsal head and heel are placed parallel to the supporting surface (Figure 1).
  • The IOS camera is positioned approximately 45cm from the foot with the device parallel to the medial aspect of the foot (Figure 1).
  • “Mask” or adjust contrast until only the dots are visible (Figure 2).
  • Select Capture Mode or “Cap”.
  • The patient shifts to full weight bearing onto the foot being measured.
  • Hips and knees positioned in frontal plane with the distal tips of contralateral toes touching the supporting surface.
  • Examiner stabilized knee vertically.
  • Relaxed Calcaneal Stance LAA was recorded automatically by the LAAngle™ app.
  • Subject body weight shifted posteriorly onto opposite foot while lifting the foot into toe off.
  • Heel elevation of 40 degrees LAA was recorded automatically by the LAAngle™ app.
  • The procedure was repeated with the contralateral foot.

Each test was repeated independently and single blind with three different examiners.  Each examiner placed the dots independently and did all recording without knowledge of prior findings.  Examinations were performed consecutively on the same visit.

Data Analysis

Interexaminer reliability were documented for the research subjects by calculating the mean absolute difference and standard deviation between paired measurements for ratio data.  Intraclass correlation coefficient [ICC(2,1)] version of the ICC was used to enable abstraction to other examiners.  Standard deviations, ranges, and mean values for males and females were calculated for each of the variables measured.

Results

Descriptive statistics for the subjects appear in Table 1.  Table 2 lists inter examiner mean absolute differences for measurement variables.   Interexaminer reliability ICC(2,1) values for subject measurement variables are presented in Table 3.  Relaxed Calcaneal Stance Position and forty degree Heel Off reliabilities ICC(2,1) were calculated via the proposed protocol utilizing the LAAngle™ App.  Table 4 lists the mean, standard deviation, and range of all subjects left and right feet absolute values for the measurement variables.

Table 1

Table 1 Descriptive statistics for male and female subjects.

The subjects consisted of fifty (50) male and thirty-five (35) female with an average age of 40.59 years with a standard deviation of 13.06, and a range of 17 to 68 years.  Average height of the subjects was 173.59cm with a standard deviation of 10.48, and a range of 154.94cm to 200.66cm.  Average weight of the subjects was 883.47N with a standard deviation of 221.54, and a range of 467.06N to 1556.88N.

Table 2

Table 2 Interexaminer mean absolute difference for subject measurement variables (N=85).

Average absolute difference between the examiners across all subjects was 8.64° with a standard deviation of 4.35 for the relaxed calcaneal stance position of the left foot, for the right foot the difference was 8.05° with a standard deviation of 4.45.  The 40° Toe off position average absolute difference was 8.08⁰ with a standard deviation of 4.35 for the left foot, right foot had an average of 9.46° with a standard deviation of 4.95.

Table 3

Table 3 Interexaminer reliability ICC(2,1) for subject measurement variables (N=85).

The Inter rater reliability for the LAA test as collected with the iOS LAAngle™ App showed that the Intraclass correlation coefficient [ICC(2,1)] in measurements of the same subject between the three examiners was 0.70 using the described protocol across all feet and genders.  The right foot had an ICC(2,1) of 0.71 for RCSP and 0.66 for 40° Heel Off.  The left foot had an ICC(2,1) of 0.70 for RCSP and .74 for 40° Heel Off.

Table 4

Table 4 Mean values, standard deviations, and ranges for subject measurement variable means (N=85).

The Average measurement values across all subjects and all feet for RCSP was 144.97° with a standard deviation of 8.93, and a range of 127.03° to 168.07°.  The average measurement values across all subjects and all feet for 40° Toe Off was 166.07° with a standard deviation of 9.35, and a range of 139.26° to 184.66°.

Discussion

The subjects came from a diverse sampling of male and female with varying heights, weights, and ages.  The majority of the subjects were born and spend most of their time in Tennessee.  The relatively heterogeneous sample supports the generalizability of the results to other populations.   Additionally, the subjects were of varying body types.  Bony prominences, therefore, may have been palpated with more or less difficulty in this sample than in other samples or populations.

The authors present a clinical test to determine the amount of postural correction possible in each patient reliably and repeatedly by determining the LAA with the foot in RCSP and toe off postures.  This fast and simple examination tool can be used in a clinical setting to determine whether or not a patient will benefit from a prescribed custom foot orthotic.  It can also be used to determine the extent of correction possible.   This affords the practitioner the ability to present third parties with justification for the use of prescription foot orthoses as well as complete documentation.

The reasoning for utilizing custom foot orthoses is that the patient’s foot posture was collapsed to a measurable quantity, the LAA.  The correction of this same foot can be achieved to the anatomical limit as determined by the measurable quantity; the LAA at 40 degrees.  Based on the results of this study, it is further postulated that the clinician or patient can use this test as stated by Heidi Burn et al to “reliably be implemented in a normal clinical environment to evaluate and assess the efficacy of prescribed foot orthoses” [9].  Meaning; the iOS LAAngle™ App can be used as a test to evaluate and assess the efficacy of current and future foot orthoses for the patient.  The degree to which custom prescribed foot orthoses can correct posture can be determined utilizing the LAAngle™ App.

Conclusion

Foot posture can be measured using the LAA and is made easier, faster, and with reliability with the iOS LAAngle™ App.  Since postural collapse, whether attributed to single axis rotation or all axis movement, is responsible for the development of many foot ailments, injuries and deformities seen in clinical practice, it is advisable to take a baseline measurement of LAA in both RCSP and elevated postures and calculate the difference in these postures in a reliable repeatable fashion for most patients with biomechanical related diagnoses.  In this way the clinician can determine the extent to which postural collapse may contribute to the patients’ disease and the extent that postural collapse can be corrected with a custom foot orthotic or surgical procedure.

Additional research is needed to determine if the change in LAA can predict the formation of foot deformity and predict the occurrence of overuse injury, plantar fasciitis, and other symptomatic conditions of the foot, ankle, knee, hip and back as well as prevent injury.

Acknowledgements  

Thanks to the employees of Sole Supports, Inc. for being subjects of the study, Sole Supports, Inc. for funding the study.

References

  1. Root M. Biomechanical examination of the foot. J Am Podiatr Med Assoc 1973;63(1):28–29. doi:10.7547/87507315-63-1-28.
  2. Gheluwe BV, Kirby KA, Roosen P, Phillips RD. Reliability and accuracy of biomechanical measurements of the lower extremities. J Am Podiatr Med Assoc 2002;92(6):317–326. doi:10.7547/87507315-92-6-317.
  3. Mcpoil TG, Hunt GC. Evaluation and management of foot and ankle disorders: present problems and future directions. J Orthop Sports Phys Ther 1995;21(6):381–388. doi:10.2519/jospt.1995.21.6.381.
  4. Bryant A, Tinley P, Singer K. A comparison of radiographic measurements in normal, hallux valgus, and hallux limitus feet. J Foot Ankle Surg 2000;39(1):39–43. doi:10.1016/s1067-2516(00)80062-9.
  5. Donatelli R. The biomechanics of the foot and ankle. Philadelphia: F.A. Davis; 1996.
  6. Jonson LSR, Gross MT. Intraexaminer reliability, interexaminer reliability, and mean values for nine lower extremity skeletal measures in healthy naval midshipmen. J Orthop Sports Phys Ther 1997;25(4):253–263. doi:10.2519/jospt.1997.25.4.253.
  7. Mcpoil TG, Cornwall MW. Use of the longitudinal arch angle to predict dynamic foot posture in walking. J Am Podiatr Med Assoc 2005;95(2):114–120. doi:10.7547/0950114.
  8. Mcpoil TG, Cornwall MW. Prediction of dynamic foot posture during running using the longitudinal arch angle. J Am Podiatr Med Assoc 2007;97(2):102–107. doi:10.7547/0970102.
  9. Burn H, Branthwaite H, Chockalingam N, Chevalier TL, Naemi R. Do foot orthoses replicate the static longitudinal arch angle during midstance in walking? The Foot 2011;21(3):129–132. doi:10.1016/j.foot.2010.12.004.
  10. Hodgson B, Tis L, Cobb S, McCarthy S, Higbie E. The effect of two custom molded orthotics on plantar pressure. J Sport Rehabil. 2006;15(1):33–44.
  11. Cobb SC, Tis LL, Johnson JT. The effect of 6 weeks of custom-molded foot orthosis intervention on postural stability in participants with ≥7 degrees of forefoot varus. Clin J Sport Med 2006;16(4):316–322. doi:10.1097/00042752-200607000-00006
  12. Trotter LC, Pierrynowski MR. Ability of foot care professionals to cast feet using the nonweightbearing plaster and the gait-referenced foam casting techniques.  J Am Podiatr Med Assoc 2008;98(1):14–18. doi:10.7547/0980014.
  13. Trotter LC, Pierrynowski MR. Changes in gait economy between full-contact custom-made foot orthoses and prefabricated inserts in patients with musculoskeletal pain.  J Am Podiatr Med Assoc 2008;98(6):429–435. doi:10.7547/0980429.
  14. Trotter LC, Pierrynowski MR. Changes in gait economy between full-contact custom-made foot orthoses and prefabricated inserts in patients with musculoskeletal pain. J Am Podiatr Med Assoc 2008;98(6):429–435. doi:10.7547/0980429.
  15. Elliott B, Garbalosa J.  The effect of maximum arch subtalar stabilization on flexible flat feet during normal walking: a case report.   Poster session presented at: Annual Fall Conference.  1st Annual  Conference of the Connecticut Physical Therapy Association; 2013; New Haven, Connecticut.

Effects of energy boost and springblade footwear on knee and ankle loads in recreational runners

by Jonathan Sinclair1pdflrg

The Foot and Ankle Online Journal 9 (2): 8

The aim of the current investigation was to comparatively examine the effects of conventional, energy boost and spring footwear on the loads experienced by the patellofemoral joint and Achilles tendon during running. Ten male runners underwent 3D running analysis at 4.0 m/s. Patellofemoral joint and Achilles tendon loads were quantified using a musculoskeletal modelling approach and contrasted between footwear using one-way repeated measures ANOVA. The results showed that peak patellofemoral force and pressure were significantly greater in conventional (force = 31.72 N/kg & pressure = 10.05 MPa) footwear in relation to energy boost (27.80 N/kg & pressure = 9.02 MPa). In addition peak Achilles tendon force was shown to be significantly greater in conventional (54.98 N/kg) compared to springblade (49.92 N/kg) footwear. On the basis that peak patellofemoral and Achilles tendon forces were significantly greater when running in conventional footwear, the findings from the current investigation indicate that utilization of conventional running footwear may place runners at increased risk from knee and ankle pathologies in comparison to energy boost and springblade shoe conditions.

Key words: springblade footwear, knee loads, ankle loads, running

ISSN 1941-6806
doi: 10.3827/faoj.2016.0902.0008

1 – Centre for Applied Sport and Exercise Sciences, School of Sport and Wellbeing, College of Health and Wellbeing, University of Central Lancashire, Preston, Lancashire, UK.
* Corresponding author: jksinclair@uclan.ac.uk


Recreational runners are renowned for their susceptibility to chronic injuries; as many as 80 % of all who participate in running activities will suffer from a chronic pathology over the course of one year [1]. The structures of the knee and ankle joints are the most common injury sites and have been shown to be associated with one-fifth of running-related injuries [1].

Given their high susceptibility to injuries, runners and clinicians/ researchers have investigated a number of different strategies which aim to attenuate the risk of injury. One such strategy is to select running footwear with appropriate mechanical characteristics; the properties of athletic footwear have been linked to the prevention of running injuries and improvement of performance and have thus been extensively investigated in biomechanical/ clinical literature.

In recent years the concept of energy return has been of interest to the footwear biomechanics community. The first footwear to incorporate the energy return principle into their design were the energy boost concept designed by Adidas. These footwear utilize an expanded thermoplastic polyurethane midsole designed to be more compliant and associated with reduced energy loss in comparison to traditional footwear midsoles. There has been only limited published research which has investigated the biomechanics of the energy boost footwear. Sinclair et al [2] examined the kinetics and kinematics of running in conventional and energy return footwear. Their findings showed that the energy boost shoes were associated with significantly increased tibial accelerations and peak eversion angles. Both Woborets et al [3] and Sinclair et al [4] showed that energy boost footwear were able to improve treadmill running economy in comparison to conventional running shoes. In addition Sinclair et al [5] demonstrated that the energy boost footwear improved running economy and reduced the bodies’ reliance on carbohydrate as a fuel source compared to minimalist footwear. In addition to the energy boost footwear a further footwear design the springblade has been introduced by Adidas which also aims to improve energy return through 16 curved blades designed to compress and release energy with each footstrike. There has yet to be any published research concerning the biomechanics of the springblade footwear, nor has there been any investigations examining knee and ankle loading in energy return footwear. Given the high incidence of knee and ankle pathologies in runners and the popularity of these new footwear models research of this nature would be of both practical and clinical significance.

Therefore, the aim of the current investigation was to comparatively examine the effects of conventional, energy boost and spring footwear on the loads experienced by the patellofemoral joint and Achilles tendon during running. Given the high incidence of knee and ankle pathologies in runners, a study of this nature may provide important clinical information to runners regarding the selection of appropriate footwear.

Methods

Participants

Ten male participants volunteered to take part in the current investigation. The mean ± SD characteristics of the participants were; age 23.59 ± 2.00 years, height 177.05 ± 4.58 cm and body mass 77.54 ± 5.47 kg. All were free from musculoskeletal pathology at the time of data collection and provided written informed consent. The procedure utilized for this investigation was approved by the University of Central Lancashire, ethical committee in accordance with the principles outlined in the Declaration of Helsinki.

Procedure

The runners completed five successful trials in which they ran through a 22 m walkway at an average velocity of 4.0 m/s in each running shoe condition. The participants struck an embedded piezoelectric force platform (Kistler Instruments) with their right foot [6]. The force platform was collected with a frequency of 1000 Hz. Running velocity was controlled using timing gates (SmartSpeed Ltd UK) and a maximum deviation of 5% from the pre-determined velocity was allowed. Kinematic information from the stance phase of the running cycle were obtained using an eight camera motion capture system (Qualisys Medical AB, Goteburg, Sweden) with a capture frequency of 250 Hz. The order in which participants performed in each footwear condition was counterbalanced. The stance phase was delineated as the duration over which > 20 N of vertical force was applied to the force platform.

Lower extremity segments were modelled in 6 degrees of freedom using the calibrated anatomical systems technique [7]. To define the segment co-ordinate axes of the foot, shank and thigh, retroreflective markers were placed bilaterally onto 1st metatarsal, 5th metatarsal, calcaneus, medial and lateral malleoli, medial and lateral epicondyles of the femur. To define the pelvis segment further markers were posited onto the anterior (ASIS) and posterior (PSIS) superior iliac spines. Carbon fiber tracking clusters were positioned onto the shank and thigh segments. The foot was tracked using the 1st metatarsal, 5th metatarsal and calcaneus markers and the pelvis using the ASIS and PSIS markers. The centers of the ankle and knee joints were delineated as the mid-point between the malleoli and femoral epicondyle markers [8,9], whereas the hip joint centre was obtained using the positions of the ASIS markers [10]. Static calibration trials were obtained allowing for the anatomical markers to be referenced in relation to the tracking markers/ clusters.

Footwear

The footwear used during this study consisted of conventional footwear (New Balance 1260 v2), energy boost (Adidas energy boost) and spring (Adidas springblade drive 2) footwear, (shoe size 8–10 in UK men’s sizes).

Processing

Dynamic trials were digitized using Qualisys Track Manager in order to identify anatomical and tracking markers then exported as C3D files to Visual 3D (C-Motion, Germantown, MD, USA). Ground reaction force and kinematic data were smoothed using cut-off frequencies of 25 and 12 Hz with a low-pass Butterworth 4th order zero lag filter. 3D kinematics of the knee and ankle were calculated using an XYZ cardan sequence of rotations (where X = sagittal plane; Y = coronal plane and Z = transverse plane). Kinematic curves were normalized to 100% of the stance phase then processed trials were averaged. Joint kinetics were computed using Newton-Euler inverse-dynamics. To quantify net joint moment anthropometric data, ground reaction forces and angular kinematics were used.

A previously utilized musculoskeletal model was used to determine patellofemoral contact force and pressure [11]. This method has been successfully utilized to resolve differences in patellofemoral contact force and pressure when wearing different footwear [12-14]. Patellofemoral joint contact force (N/kg) during running was then estimated as a function of knee flexion angle (Kfa) and knee extensor moment (ME) according to the biomechanical model described by Ho et al [15]. Firstly, the moment arm of the quadriceps muscle (mq) was calculated as a function of knee flexion angle using non-linear equation, which is based on cadaveric information presented by van Eijden et al [16]:

mq = 0.00008 Kfa3 – 0.013 Kfa2 + 0.28 Kfa + 0.046

Quadriceps force (QF) was then calculated using the below formula:

QF = ME / mq

PTF was estimated using the QF and a constant (K):

PTF = QF K

The constant was described in relation to the fa using a curve fitting technique based on the non-linear equation described by Eijden et al [16]:

K = (0.462 + 0.00147 Kfa2 – 0.0000384 fa2) / (1 – 0.0162 Kfa + 0.000155 Kfa 2 – 0.000000698 Kfa 3)

Patellofemoral pressure (MPa) was calculated as a function of the patellofemoral contact force divided by the patellofemoral contact area. The contact area was described in accordance with the Ho et al [15] recommendations by fitting a second-order polynomial curve to the data of Powers et al [17] who documented patellofemoral contact areas at varying levels of knee flexion.

Patellofemoral pressure = patellofemoral contact force / contact area

Achilles tendon force (N/kg) was determined using a previously utilized musculoskeletal model. This model has been used previously to resolve differences in Achilles tendon force between footwear [14,18].  Achilles tendon force was quantified as the plantarflexion moment (MPF) divided by the estimated Achilles tendon moment arm (mat). The moment arm was quantified as a function of the ankle sagittal plane angle (ak) using the procedure described by Self and Paine [19]:

Achilles tendon force = MPF / mat

mat = -0.5910 + 0.08297 ak – 0.0002606 ak2

Average patellofemoral contact force and Achilles tendon load rate were quantified as the peak patellofemoral contact force / Achilles tendon force divided by the time over which the peak force occurred. Instantaneous patellofemoral/ Achilles tendon load rate were also determined as the peak increase in patellofemoral contact force/ Achilles tendon force between adjacent data points. In addition to this we also calculated the total patellofemoral contact force/ Achilles tendon force impulse (N/kg·s) during running by multiplying the patellofemoral contact force/ Achilles tendon force estimated during the stance phase by the stance time.

Analyses

Means and standard deviations were calculated for each outcome measure for all footwear conditions. Differences in Achilles tendon force and patellofemoral contact force parameters between footwear were examined using one-way repeated measures ANOVAs, with significance accepted at the P≤0.05 level. Effect sizes were calculated using partial eta2 (pη2). Post-hoc pairwise comparisons were conducted on all significant main effects. The data was screened for normality using a Shapiro-Wilk which confirmed that the normality assumption was met. All statistical actions were conducted using SPSS v22.0 (SPSS Inc., Chicago, USA).

Results

Tables 1-2 and figure 1 present the knee and ankle loads during the stance phase of running, as a function of the different experimental footwear. The results indicate that footwear significantly influenced both knee and ankle kinetic parameters.

Fig1

Figure 1 Knee and ankle loads as a function of footwear; a. = Patellofemoral contact force, b. = Patellofemoral pressure, c. = Achilles tendon force (black = energy boost, grey = springblade, dash = conventional).

Conventional Energy return Spring
Mean SD Mean SD Mean SD
Peak patellofemoral contact force (N/kg) 31.72 6.37 27.80 5.70 30.17 4.73
Time to patellofemoral contact force (s) 0.09 0.01 0.08 0.01 0.08 0.01
Patellofemoral load rate (N/kg/s) 372.34 53.13 334.11 60.83 356.99 34.94
Patellofemoral instantaneous load rate (N/kg/s) 1470.35 561.44 1435.06 529.05 1532.02 372.51
patellofemoral contact force impulse (N/kg·s) 2.84 0.90 2.26 0.68 2.58 0.82
Patellofemoral pressure (MPa) 10.05 1.87 9.02 1.71 9.70 1.38

Table 1 Knee loads as a function of footwear.

Conventional Energy return Spring
Mean SD Mean SD Mean SD
Peak Achilles tendon force (N/kg) 54.98 7.73 52.40 8.50 49.92 7.21
Time to Achilles tendon force (s) 0.13 0.02 0.13 0.02 0.13 0.01
Achilles tendon load rate (N/kg/s) 449.21 110.49 436.33 138.79 381.65 88.49
Achilles tendon instantaneous load rate (N/kg/s) 1316.78 387.07 1114.70 342.44 1377.57 570.81
Achilles tendon force impulse (N/kg·s) 6.23 1.26 5.82 1.22 5.88 1.06

Table 2 Ankle loads as a function of footwear.

Knee loads

A main effect (P<0.05,2=0.32) was found for peak patellofemoral contact force. Post-hoc analyses indicated that peak patellofemoral contact force was significantly greater in conventional footwear compared to energy boost (Table 1; Figure 1a). A main effect (P<0.05,2=0.29) was similarly for peak patellofemoral pressure. Post-hoc analyses indicated that peak patellofemoral pressure was significantly greater in conventional footwear compared to energy boost (Table 1; Figure 1b). There was also a main effect for (P<0.05,2=0.33) patellofemoral load rate. Post-hoc analyses indicated that peak patellofemoral load rate was significantly greater in conventional footwear compared to energy boost (Table 1). A main effect (P<0.05,2=0.31) was shown for patellofemoral impulse. Post-hoc analyses indicated that patellofemoral impulse was significantly greater in conventional footwear compared to energy boost (Table 1).

Ankle loads

A main effect (P<0.05,2=0.30) was found for peak Achilles tendon force. Post-hoc analyses indicated that peak Achilles tendon force was significantly greater in conventional footwear compared to springblade (Table 2; Figure 1c).

Discussion

The aim of the current investigation was to comparatively examine the effects of conventional, energy boost and spring footwear on the loads experienced by the patellofemoral joint and Achilles tendon during running. To the authors knowledge this represents the first investigation to comparatively investigate knee and ankle loads when running in energy boost and spring footwear.

The first key finding from the current study is that patellofemoral contact force and contact pressure were shown to be significantly greater in the conventional footwear in relation to the energy boost condition. This finding is in agreement with the findings of Sinclair, [14] and Bonacci et al [12] who confirmed that different footwear can significantly influence patellofemoral loading magnitude. This observation may be important clinically with regards to the aetiology of patellofemoral disorders in runners. Patellofemoral pain syndrome is is considered to be caused by repeated high loads that are imposed too frequently to the patellofemoral joint itself [15]. Therefore the findings this study indicate that the energy boost footwear may be the most efficacious for runners who are susceptible to patellofemoral joint conditions.

A potential limitation of previous research investigating the effects of different running footwear on the forces experienced by the musculoskeletal system when running is that only the peak forces experienced per step have been reported. Therefore the potential effects that alterations in stance time/ stride frequency may have on the summative loads experienced by the body are not accounted for. The findings from the current investigation can be further contextualized by examining the patellofemoral impulse associated with each footwear. The findings for patellofemoral impulse mirror those in relation to peak patellofemoral force in that energy boost footwear significantly reduced impulse, giving further support to the earlier proposition that these footwear may be able reduce the likelihood of experiencing patellofemoral pain symptoms in runners.   

A further important finding from the current study is that Achilles tendon load was shown to be significantly larger in the conventional footwear in comparison to the springblade shoes. This observation similarly concurs with the findings of Sinclair, [14] who showed that different footwear significantly influenced Achilles tendon force. This observation may also be relevant clinically with regards to the aetiology of Achilles tendon pathologies in runners. The aetiology of Achilles tendinosis relates to repeated high loads applied too frequently to the tendon itself without sufficient rest [20]. Loads exceeding the tendons physiological threshold mediate collagen degradation which ultimately leads to injury [21]. Therefore the findings from the current investigation indicate that the springblade footwear may be most appropriate for runners who are susceptible to Achilles tendon pathologies.

In conclusion, although energy return footwear have been investigated extensively in biomechanics research, the current knowledge regarding the effects of energy boost and springblade footwear on patellofemoral contact and Achilles tendon forces is limited. The present investigation therefore adds to the current knowledge by providing a comprehensive evaluation of patellofemoral and Achilles tendon force parameters when running energy boost, springblade and conventional footwear. On the basis that patellofemoral and Achilles tendon force were significantly greater when running in conventional footwear, the findings from the current investigation indicate that utilization of conventional running footwear may place runners at increased risk from knee and ankle pathologies in comparison to energy boost and springblade shoe conditions.

References

  1. van Gent, R, Siem DD, van Middelkoop M, van Os TA, Bierma-Zeinstra SS, Koes, BB. Incidence and determinants of lower extremity running injuries in long distance runners: a systematic review. British Journal of Sports Medicine 2007: 41: 469-480. (PubMed)
  2. Sinclair, J, Franks, C, Goodwin, JF, Naemi, R, Chockalingam, N. Influence of footwear designed to boost energy return on the kinetics and kinematics of running compared to conventional running shoes. Comparative Exercise Physiology 2014; 10: 199-206. (Link)
  3. Worobets, J, Wannop, JW, Tomaras, E, Stefanyshyn, D. Softer and more resilient running shoe cushioning properties enhance running economy. Footwear Science 2014; 6: 147-153. (Link)
  4. Sinclair, J, Mcgrath, R, Brook, O, Taylor, PJ, Dillon, S. Influence of footwear designed to boost energy return on running economy in comparison to a conventional running shoe. Journal of Sports Sciences, 2016; 34: 1094-1098. (PubMed)
  5. Sinclair, J., Shore, H., Dillon, S. (2016). The effect of minimalist, maximalist and energy return footwear of equal mass on running economy and substrate utilization. Comparative Exercise Physiology (In press).
  6. Sinclair J, Hobbs SJ, Taylor PJ, Currigan G, Greenhalgh A. The Influence of Different Force and Pressure Measuring Transducers on Lower Extremity Kinematics Measured During Running. Journal of Applied Biomechanics 2014 30: 166–172. (PubMed)
  7. Cappozzo A, Catani F, Leardini A, Benedeti MG, Della CU. Position and orientation in space of bones during movement: Anatomical frame definition and determination. Clinical Biomechanics 1995; 10: 171-178. (PubMed)
  8. Graydon, R, Fewtrell, D, Atkins, S, Sinclair, J. The test-retest reliability of different ankle joint center location techniques. Foot Ankle Online J. 2015; 8: 1-11. doi: 10.3827/faoj.2015.0801.0011
  9. Sinclair, J, Hebron, J, Taylor, PJ. The Test-retest Reliability of Knee Joint Center Location Techniques. Journal of Applied Biomechanics 2015; 31: 117-121. doi: 10.1123/jab.2013-0312
  10. Sinclair, J, Taylor, PJ, Currigan, G, Hobbs, SJ. The test-retest reliability of three different hip joint centre location techniques. Movement & Sport Sciences. 2014; 83: 31-39. doi: (Link)
  11. Ward SR, Powers CM. The influence of patella alta on patellofemoral joint stress during normal and fast walking. Clinical Biomechanics 2004; 19: 1040–1047. (PubMed)
  12. Bonacci J, Vicenzino B, Spratford W, Collins P. Take your shoes off to reduce patellofemoral joint stress during running. British Journal of Sports Medicine, (In press). (Link)
  13. Kulmala JP, Avela J, Pasanen K, Parkkari J. Forefoot strikers exhibit lower running-induced knee loading than rearfoot strikers. Medicine & Science in Sports & Exercise 2013; 45: 2306-2313. (PubMed)
  14. Sinclair J. Effects of barefoot and barefoot inspired footwear on knee and ankle loading during running. Clinical Biomechanics 2014; 29: 395-399. (PubMed)
  15. Ho, KY, Blanchette MG, Powers CM. The influence of heel height on patellofemoral joint kinetics during walking. Gait & Posture 2012; 36: 271-275. (PubMed)
  16. van Eijden TM, Kouwenhoven E, Verburg J, Weijs WA. A mathematical model of the patellofemoral joint. Journal of Biomechanics 1986; 19: 219–229, 1986. (PubMed)
  17. Powers CM, Lilley JC, Lee TQ. The effects of axial and multiplane loading of the extensor mechanism on the patellofemoral joint. Clinical Biomechanics 1998; 13: 616–624. (PubMed)
  18. Sinclair, J, Taylor, PJ, Atkins, S. Influence of running shoes and cross-trainers on Achilles tendon forces during running compared with military boots. Journal of the Royal Army Medical Corps 2015; 161: 140-143. (PubMed)
  19. Self, BP, Paine, D. Ankle biomechanics during four landing techniques. Medicine & Science in Sports & Exercise 2001; 33: 1338–1344.
  20. Selvanetti, ACM, Puddu, G. Overuse tendon injuries: basic science and classification. Operative Techniques in Sports Medicine 1997; 5: 110–17. (Link)
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Steroid intra-articular injections for foot and ankle conditions: How effective are they?

by Mohammed KM Ali1*, Suhayl Tafazal1, CA Mbah1, D Sunderamoorthy1pdflrg

The Foot and Ankle Online Journal 9 (2): 7

Purpose: Intra–articular steroid injection is commonly given for the non-operative management of foot and ankle arthritis; however, there is little evidence in the literature about the effectiveness of these injections. The aim of our study was to assess the effectiveness of injections given for the treatment of foot and ankle arthritis.
Methods: We retrospectively reviewed the prospectively collected data of 64 foot and ankle injections done over a period of 12 months. 0.5% Chirocaine and 40 mg of Kenalog was used for the injection. A visual analogue score was used to determine the efficacy of the injection.
Results: The mean follow up was 12 months. 84% (54/64) patients had significant pain relief following the foot and ankle injection. 16% (10/64) went on to have further procedures at six months.  There were 6 patients with ankle arthritis in whom the injection effect did not last more than six months. Two had arthroscopic debridement, two had fusion and of the remaining two patients, one was not fit for surgery and the last one declined surgical intervention. Additionally at six months there were two patients with midfoot OA and two with hindfoot OA, who required further procedures. Patients with no remaining  symptoms were either discharged or given an open appointment.
Conclusions: Our study has shown that patients receiving an intra-articular steroid injection for forefoot conditions have positive outcomes following the injection for six months. Whereas 22% of patients having an intra-articular steroid injection for the ankle, hindfoot and midfoot arthritis have failed to maintain the symptom relief at six months and required further intervention.. This information is useful when obtaining an informed consent from the patient receiving an  intra-articular injection for foot and ankle conditions.

Key words: steroid injections, arthritis, intra-articular injection, foot, ankle

ISSN 1941-6806
doi: 10.3827/faoj.2016.0902.0007

1 – Trauma and Orthopaedics, Royal Derby Hospital, United Kingdom.
* Corresponding author: Mohammedkhider84@hotmail.com


Intra-articular injections into foot and ankle joints are used for therapeutic and diagnostic purposes. Injection of local anaesthetic may provide temporary relief of pain and suggests the joint as the source of symptoms; inclusion of a corticosteroid in the injection may diminish inflammation from various causes to alleviate pain [1]. Mitchell et al. reported selective intra-articular injections afford a direct method of confirming the site of hindfoot pain and may aid in surgical planning [2].

Osteoarthritis (OA) is the most common form of joint disease and a leading cause of disability in the elderly. The etiology is multi-factorial, with  a variety of risk factors such as aging, genetics, trauma, malalignment, and obesity, which interact to cause this disorder [3]. Foot and ankle arthritis can cause substantial pain and functional limitation and intra–articular corticosteroids are commonly used as a non-operative treatment for pain relief [4].

Intra-articular corticosteroids have previously been shown to offer good pain relief in patients with knee, hip or shoulder OA; however there is little evidence in the literature about the effectiveness of foot and ankle injections [5-8]. The aim of this study is to evaluate the efficacy of intra-articular corticosteroid injection in patients with Foot and ankle OA.

Materials and Methods

We performed a retrospective review of prospectively collected data of 64 patients who had foot and ankle injections between July 2013 to June 2014. The most common indication for injection was osteoarthritis of the joint involved. Each patient was evaluated clinically and radiologically by the Senior Author (DS) to determine the need for the intra-articular injection. We also recorded age, sex, diagnosis, symptoms duration and any relevant co-morbidities.
0.5% Chirocaine and 40 mg of Kenalog (Triamcinolone) was used for the injections. All the injections were performed by the Senior Author (Foot & Ankle Consultant) in the operative theatre using Image Intensifier guidance. Patients were then seen at 12 weeks and  six months. Based on their symptoms at six months, patients either had further procedures, discharged or given an open appointment. The primary efficacy outcomes were a reduction in global pain. A 0–10 Visual Analog Scale (VAS) was used for global pain measurement. VAS was recorded along the different visits (Figure 1).

fig1

Figure 1 Visual analogue score

Injection site Number of patient Joints involved
Ankle 28/64 (44%) Ankle joint (28)
Hindfoot 10/64 (16%) Talonavicular (7),

Calcaneocuboid (3)

Midfoot 10/64 (16%) Tarsometatarsal (10)
Forefoot 16/64 (28%) Metatarsophalangeal (11)

Interphalangeal joints (5)

 

Table 1 Demonstrating the number of patient in each group arranged by injection site location.

Results

Sixty four patients were studied: twenty four males and forty females. The average age was fifty four years (range 37 to 79 yrs). Mean follow up was 12 months. Patients had mean duration of symptoms of three years (range one to five years). Patients were put into four groups, according to the site of the injections (Table 1).

The initial VAS average was nine, with a range from six to 10. 84% (54/64) of patients had significant pain relief following the foot and ankle injection with a VAS below five that lasted more than six months. In 16% (10/64) of the patient’s symptoms remained and they went on to have further intervention (surgery/ arthroscopy) (Table 2).

Pre op pain score  average 9 (6-10)
Post op pain score  84% <5 average 3

 16% >5 average 8

Table 2 Overall pain score; pre and post injections.

Injection site

(No of pts)

VAS pre-inj

Mean (range)

VAS at 12 weeks Mean (range) Patients had more injections VAS at 6 months  Mean (range) Patients needed further Procedure
Ankle joint

28

8 (6-10) 5 (3-9) 5 patients 6 (4-10) 6 patients

5 had inj at 6 months+ 1 new)

Hind-foot

10

9 (8-10) 4 (0-8) 3 patients 6 (4-8) 2 patient

(both had inj at 6 months)

Mid –foot

10

9 (7-10) 3 (3-5) 1 patients 5 (3-10) 2 patients

(1 had inj at 6 months)

Fore-foot

16

9 (8-10) 3 (0-4) none 3 (0-5)

4 did not attend

None

Table 3 Pre and post injections VAS

At 12 weeks; the injections failed to provide pain relief in nine patients and they all were provided further injections. At six months; eight out of those nine patients continued to have symptoms after the second injections and required surgical interventions. Additionally  there were  two patients who had one injection initially and presented after six months with worsening symptoms (Table 3).

There were six patients with ankle arthritis in whom the injection effect did not last more than six months. Two had arthroscopic debridement, two had fusions (Figures 2 and 3), one was not fit for surgery and the last one declined it. Additionally t 6 months 2 patients with midfoot OA and two  with hindfoot OA, who required further intervention (Table 4).

Age sex Duration of symptoms

Months

Co-morbidities Investigation Diagnosis Pre inj

VAS

12 weeks post inj VAS 6 mo

VAS

More injections Further surgery?
48 F 18 RA MRI 2, 3rd TMTJ

Arthritis

10 06 10 No Fusion
49 F 24 None X rays Ankle OA 10 09 09 No Arthroscopic

Debridement

60 M 60 Pilon Fracture CT

X rays

Ankle OA

Post-traumatic

10 03 10 No Fusion
70 F 48 None CT 2, 3rd TMTJ

Arthritis

10 05 10 No Fusion
79 M 120 Cardiac problems X rays Ankle OA 08 10 10 No Not fit for surgery
39 M 36 Calcaneus fracture CT

X rays

Subtalar OA 09 09 09 No Fusion
54 F 30 None X rays Ankle OA 10 08 10 No Arthroscopic

Debridement

67 M 60 None X rays Talo-Nav, Calc-Cub OA 08 06 08 No Fusion
63 M 36 Hip OA X rays Ankle OA 08 08 08 No Declined surgery
72 M 36 None CT

X rays

Ankle OA 10 03 10 No Fusion

Table 4  Patients who required further intervention at six months post injection.

fig2

Figure 2 Second and third tarsometatarsal joint fusion.

Discussion

Cortisone was first used in the treatment of rheumatoid arthritis in the late 1940s [3] and in 1950; Thorn was the first to inject steroids into the knee of a patient with rheumatoid arthritis [4]. In the beginning, the results were somewhat disappointing, however, it later became clear that cortisone is dependent for its action on hydroxylation to hydrocortisone in the liver. Direct injection of hydrocortisone gave better results, but the effect was only transient. The development of less soluble esters provided steroids with longer half-lives and long term effectiveness [5]. The rate of systemic absorption of an intra-articular corticosteroid is related to the solubility of the compound, and it is understood that more insoluble corticosteroid compounds are better suited to intra-articular use as the local duration of action may be prolonged and effects due to systemic absorption are kept to a minimum [6]. Triamcinolone Acetonite (Kenalog) has an extended duration of effect which may be sustained over a period of several weeks and for reasons related to availability and cost, as well as pharmacokinetics, was the  steroid used in this clinical investigation.

fig3

Figure 3  Ankle OA intraoperatively during fusion procedure.

Intra-articular corticosteroids remain widely used for symptomatic treatment of peripheral joint osteoarthritis, although the duration of the effect can be highly variable depending on many factors,  such as type of  joint involved and the use of image guidance or not [7-11].

Kevin et al suggest experienced surgeons may be able to place intra-articular injections without fluoroscopy in a normal posterior subtalar joint with a 97% accuracy rate [1]. Fluoroscopy may not be necessary for injections used solely for therapeutic purposes. However, if the injection is intended for diagnostic purposes and surgical decision making for potential arthrodesis or if the joint is abnormal, they recommend fluoroscopy to ensure accurate placement without extension or extravasations into nearby structures that also might be potential sources of pain. Concerns for surrounding soft tissues may warrant use of fluoroscopy in cases of arthrosis and indwelling hardware [1]. Similarly Khoury et al. reported injections performed under fluoroscopic control allowed confirmation of the painful joint, which in turn led to successful patient outcomes after arthrodesis [12]. All our patients had the intra-articular steroid injection under fluoroscopy guidance as suggested in the literature to improve the accuracy of the injections.

Ward et al in a prospective one year follow up of intra-articular steroid injection of the foot and ankle has shown a statistically significant foot and ankle score improvement following corticosteroid injection up to and including six months post-injection. No independent clinical factors were identified that could predict a better post-injection response.

The magnitude of the response at two months was found to predict a sustained response at nine months and one year. Intra-articular corticosteroids improved symptom scores in patients with foot and ankle arthritis. The duration of this response was varied and patient factors affecting the response remain unclear. Response to the injection at two months can be used to predict the duration of beneficial effects up to at least one year [13].

In our study, there was a statistically significant improvement in foot and ankle scores above the starting point using the visual analogue score.  84% (54/64) of the patients had an appreciable pain relief up to six months post injection. Only 16% (10/84) of the patients needed further procedures at six months and in the majority of them. At 12 weeks; the injections failed to provide pain relief in nine patients and they all were provided further injections. At six months; eight out of those nine patients continued to have symptoms after the second injections and required surgical interventions. Similar to Ward et al findings our study has shown a similar result in a poor outcome at 12 weeks correlates well with the long term outcome resulting in further injection or surgical intervention.

Furthermore, our study has shown that patients having forefoot injections had a good outcome with none of them requiring surgical intervention at one year. Whereas the ankle, hindfoot and midfoot injections had a failure rate of 22% resulting in surgical intervention.  There is no evidence in the literature of the failure rate of the injections and the percentage of patients requiring surgical intervention for the injection failure. Our study is the first one to show that failure rate for the different regions of the foot and ankle over a one year period.

The above evidence would be a useful tool when it comes to obtaining  informed consent for patients having foot and ankle injections.
This study was limited by a number of weaknesses. Our sample size, although sufficient to identify statistically significant differences for some of the factors that we measured, was possibly too small for us to detect other statistically significant factors, should they have presented.

We assumed that the joints identified by the foot and ankle surgeon as the source of symptoms, in fact, were the cause of our patients’ foot pain. If this diagnosis was inaccurate, or if other unidentified joints or pathology were contributing to the participant’s symptoms, this would have biased our results toward the null.

Conclusion

Our study has shown that patients having intra-articular steroid injection for forefoot conditions have good outcome following the injection and they maintain it at six months. Whereas approximately 22% of patients receiving intra-articular steroid injection for arthritis of the ankle, hindfoot or  midfoot,  have failed to remain free of symptom sat six months and required further intervention. This information is useful when obtaining an informed consent from the patient receiving  an intra-articular injection for foot and ankle conditions, in order to provide them with realistic expectations for treatment.

References

  1. Kirk KL, Campbell JT, Guyton GP, Schon LC. Accuracy of posterior subtalar joint injection without fluoroscopy. Clin Orthop Relat Res. 2008;466(11):2856-60.
  2. Mitchell MJ, Bielecki D, Bergman AG, Kursunoglu-brahme S, Sartoris DJ, Resnick D. Localization of specific joint causing hindfoot pain: value of injecting local anesthetics into individual joints during arthrography. AJR Am J Roentgenol. 1995;164(6):1473-6.
  3. Hench PS, Slocumb CH. The effects of the adrenal cortical hormone 17-hydroxy-11-dehydrocorticosterone (Compound E) on the acute phase of rheumatic fever; preliminary report. Proc Staff Meet Mayo Clin. 1949;24(11):277-97.
  4. Hollander JL. Intra-articular hydrocortisone in arthritis and allied conditions; a summary of two years’ clinical experience. J Bone Joint Surg Am. 1953;35-A(4):983-90.
  5. Grillet B, Dequeker J. Intra-articular steroid injection. A risk-benefit assessment. Drug Saf. 1990;5(3):205-11.
  6. Derendorf H, Möllmann H, Grüner A, Haack D, Gyselby G. Pharmacokinetics and pharmacodynamics of glucocorticoid suspensions after intra-articular administration. Clin Pharmacol Ther. 1986;39(3):313-7.
  7. D’agostino MA, Ayral X, Baron G, Ravaud P, Breban M, Dougados M. Impact of ultrasound imaging on local corticosteroid injections of symptomatic ankle, hind-, and mid-foot in chronic inflammatory diseases. Arthritis Rheum. 2005;53(2):284-92.
  8. Peterson CK, Buck F, Pfirrmann CW, Zanetti M, Hodler J. Fluoroscopically guided diagnostic and therapeutic injections into foot articulations: report of short-term patient responses and comparison of outcomes between various injection sites. AJR Am J Roentgenol. 2011;197(4):949-53.
  9. Friedman DM, Moore ME. The efficacy of intraarticular steroids in osteoarthritis: a double-blind study. J Rheumatol. 1980;7(6):850-6.
  10. Gaffney K, Ledingham J, Perry JD. Intra-articular triamcinolone hexacetonide in knee osteoarthritis: factors influencing the clinical response. Ann Rheum Dis 1995;54:379-81.
  11. Dieppe P, Cushnaghan J, Jasani MK, McCrae F, Watt I. A two-year, placebo-controlled trial of non-steroidal anti-inflammatory therapy in osteoarthritis of the knee joint. Br J Rheumatol 1993;32(7):595-600.
  12. Khoury NJ, el-Khoury GY, Saltzman CL, Brandser EA. Intraarticular foot and ankle injections to identify source of pain before arthrodesis. AJR Am J Roentgenol. 1996;167:669–673.
  13. Ward ST, Williams PL, Purkayastha S. Intra-articular corticosteroid injections in the foot and ankle: a prospective 1-year follow-up investigation. J Foot Ankle Surg. 2008;47(2):138-44.
  14. Kumar N, Newman RJ. Complications of intra- and peri-articular steroid injections. Br J Gen Pract. 1999;49(443):465-6.

Lateral and open medial subtalar dislocation: Report of two uncommon cases

by Ganesh Singh Dharmshaktu1* , Irfan Khan2pdflrg

The Foot and Ankle Online Journal 9 (2): 6

Subtalar or peritalar dislocation is a rare injury and limited to a small number of reported cases. The proper and early diagnosis and judicious management is paramount to good functional outcome. The documentation of other associated injuries and respective management is also crucial. We present two cases describing each of the two variants i.e. medial and lateral subtalar dislocation. These cases add value to existing literature by strengthening the knowledge about early identification and appropriate management of such uncommon pattern of injuries.

Key words: subtalar joint, dislocation, medial subtalar dislocation, lateral subtalar dislocation, closed reduction.

ISSN 1941-6806
doi: 10.3827/faoj.2016.0902.0006

1* – Assistant Professor , Department of Orthopaedics, Government Medical College, Haldwani , Uttarakhand. drganeshortho@gmail.com
2 – Senior Residnt , Department of Orthopaedics, Government Medical College, Haldwani , Uttarakhand.


Subtalar dislocation, also referred as peritalar dislocation, is an uncommon injury pattern and may or may not involve associated talar fracture. The incidence has been reported to be 0.9% (42 cases in a series of 4215 dislocations) in one series [1]. Another series reported its incidence of 15% of all talar injuries[2]. Initially regarded as a traumatic event in young adults, recent observations reveal sizeable number of patients beyond forty years of age [3]. The injury usually presents with deformed anatomy, and medial dislocation is more common[4]. Lateral dislocation are associated with higher energy injuries and carry a worse prognosis of the two. Motor vehicle accidents, fall from height, and sports injury are common mechanisms of these injuries. Apart from the primary dislocation, the frequent presence of open injuries requires careful soft tissue handling and asepsis in the treatment [5]. Two cases of both types of dislocation including one with small a open wound is presented here with appropriate management and good outcomes.

Case Reports

Case 1  

A 26-year-old male patient presented to us with history of road traffic accident two hours prior to presentation, after getting hit by a moving car while cycling, and his right foot got stuck under the bike after falling to the ground. The exact mechanism and position of the foot at the time of impact could not be recalled by the patient and he noticed a deformity and inability to bear weight since the injury. The deformity involved the foot to be appearing lateral. There was mild swelling at presentation and active toe movement along with an intact distal neurovascular status. A small 2cm open wound at lateral aspect of the ankle was present that was apparently uncontaminated (Figure 1). Prompt radiological evaluation was ordered to reveal a medial subtalar dislocation without noticeable fracture (Figure 2). Urgent reduction under anesthesia was planned.

The talus appeared to remain at normal location while the structures below it were displaced medially along with talonavicular dislocation. A through copious lavage was done through the wound. The reduction was done by traction and initially accentuating the deformity and reducing by digital pressure over the talus and giving lateral force to the foot for a smooth reduction. The reduction was confirmed on image intensifier for restoration of normal foot anatomy in biplanar views before applying a plaster protection splint (Figure 3). The limb was elevated and pain medications were given as active toe movements were encouraged throughout treatment.

fig1

Figure 1 Clinical picture of case with medial dislocation and small lateral wound.

fig2

Figure 2 The radiograph of medial subtalar dislocation of right foot in both planes.

fig3

Figure 3 Post-reduction radiograph showing good reduction stabilized with plaster slab.

Case 2

A 53-year-old male patient hit and twisted his right foot after fall from a height of six feet into hard ground five hours prior to presentation. The weight of the body was concentrated on ankle and foot region at ground strike. His foot was everted as he fell followed by body weight over the area leading to deformity and pain. There was painful restriction of ankle movement and unable to ambulate. He was taken to a local clinic where a cardboard make-do splint was provided before consultation. There was no open wound or distal neurovascular deficit present. His radiograph showed a lateral subtalar dislocation with a small bony fragment between the navicular and talus in lateral view, suggestive of probable osteochondral fracture of talus (Figure 4). He was posted for urgent reduction under anaesthesia following informed consent. Slight traction and accentuation of deformity by eversion followed by inward foot pressure with counter-pressure at navicular bone resulted in successful reduction.

The reduction was assessed under image intensifier followed by plaster back-slab (Figure 5). The further management and the results were similar to the first case and uncomplicated recovery and follow up period was noted. The patient was lost to follow up after ten months.

fig4

Figure 4 The radiograph of lateral subtalar dislocation of right foot in both planes, and a small osteochondral fragment from navicular is also noted.

fig5

Figure 5 Post-reduction radiograph showing good reduction stabilized with plaster slab.

Results

The follow up period was uneventful and there were no recurrence noted. The patients gradually started protected weight bearing after rest of four weeks for optimal soft tissue healing and reduction of swelling. Supervised physiotherapy was instrumental in regain of function and ambulation. The follow up of fourteen weeks was unremarkable and patients were pursuing activities of daily living.

Discussion

The characteristic deformities following subtalar dislocation resemble an ‘acquired clubfoot’ and ‘acquired flatfoot’ in cases of medial and lateral dislocation respectively [6]. Other regional or remote injuries including small osteochondral fractures need to be searched and treated accordingly as they involve a large portion of cases[3-5,7]. Skin tenting should be relieved by prompt reduction to avoid complication. Open wounds should be thoroughly lavaged and debrided before closure [8]. Reduction is preferably done with complete muscle relaxation and often accentuation of deformity by either inversion or eversion maneuver for medial and lateral dislocations respectively. This reduction maneuver is well described in the literature and was followed by us to an uneventful outcome [9]. The reduction usually is achieved in closed manner but adjacent tissue and other structures might impede reduction at times and require open reduction. Shortest possible immobilization has been advocated followed by physical therapy to regain subtalar and midtarsal mobility. Conservative management has been an excellent modality with good results in previous studies[4,10]. Both of our cases had a successful result of uneventful closed reduction and satisfactory functional outcome.

References

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Form determines function: Forgotten application to the human foot?

by Mick Wilkinson, PhD1* and Lee Saxby, BSc1pdflrg

The Foot and Ankle Online Journal 9 (2): 5

There has been and continues to be much debate about the merits and detriments of barefoot and minimal-shoe running. Research on causes of running-related injury is also characterised by equivocal findings. A factor common to both issues is the structure and function of the foot. Comparatively, this has received little attention. This perspective piece argues that foot function and in particular, how foot structure determines function, has largely been overlooked, despite basic principles of physics dictating both the link between structure and function and the importance of function for stability in locomotion. We recommend that foot shape and function be considered in the interpretation of existing findings and be incorporated into future investigations interested in running mechanics, injury mechanisms and the effects of footwear on both.

Key words: human foot, mechanics, barefoot, locomotion

ISSN 1941-6806
doi: 10.3827/faoj.2016.0902.0005

1 – Sport, Exercise and Rehabilitation, Northumbria University, UK.
* Correspondence – Mic.wilkinson@northumbria.ac.uk


As stated by evolutionary biologist EO Wilson, “everything in biology is subject to the laws of physics and chemistry and has arisen through evolution by natural selection” [1]. Applying this logic to the study of human locomotion, and in particular the structure and role of the foot, can bring clarity to the interpretation of many past and recent studies on barefoot-versus-shod-and minimal-shoe locomotion, and the associated benefits and risks. Using laws and undisputed theories as filters through which to interpret study outcomes can provide a context to equivocal findings and also suggest fruitful lines of future inquiry.

The ‘purpose’ of the foot

Assigning a purpose to a biological structure is often criticised as teleological. However, as Nobel Laureate Albert Szent-Gyorgyi [2] wrote “teleology resembles an attractive lady of doubtful repute whose company we cherish but in whose company we do not like to be seen”. Purpose provides the context without which many observations in nature make no sense. A teleological view is therefore adopted in this piece.
In an upright biped, the purpose of the foot is to support and control the direction of the body weight as it falls forwards during the stance phase of locomotion [3-5]. With this and fundamental physics in mind, a reverse-engineering approach suggests a larger base of support, that is widest at the front, would serve both purposes.

It is not surprising therefore, that comparisons of habitually-unshod with habitually-shod populations consistently show wider (particularly at the front) feet in unshod populations, in agreement with that predicted by fundamental principles [6-10]. Studies on habitually-barefoot populations also demonstrate the benefits of a wide base of support in the form of more uniform distribution of pressure through the entire plantar surface during walking [9], and reduced peak pressure and pressure-time integral under the forefoot in running [11].

Structure determines function

There has been recent attention on the role of intrinsic foot musculature [12] and how barefoot / minimal footwear use might influence their strength and function [13]. However, it must be remembered that these muscles simply respond to the forces acting on them [3,12]. In the foot, the magnitude and direction of these forces will be partly determined by the shape of the foot, and in particular by the position of the hallux [14,15]. It has been suggested that the thickness, length and position of the hallux represents evolutionary adaptation to terrestrial-bipedal locomotion [14,16-19]. The effect of foot shape on control of the path of body weight through the foot has long been established and is explained by simple physics [14]. This questions a research focus on the strength and /or training of intrinsic-foot musculature without consideration of foot shape, as it is unlikely that strength of muscles in a structurally-compromised foot could overcome gravity and the ground-reaction force as effectively as a structurally-sound foot.

A logical prediction from an engineering view of an ideal foot is that a wider foot would offer a more stable base over which to pass the body weight, and a larger surface area over which to distribute pressure. Here, the hallux is of special importance [15]. Morton [14] demonstrated that the hallux position, secondary to a correctly aligned first metatarsal, directed body weight in the sagittal plane through the axis of leverage between the first and second metatarsal heads.

He also demonstrated that a valgus position of the hallux resulted in excessive pronation, as the hallux was not mechanically positioned to control and direct the path of the body weight in the sagittal plane. This resulted in transfer of motion into the transverse and frontal planes. Chou et al [15] reported impaired single-leg balance and directional control of weight shifting when hallux use was constrained by a purpose-made splint. A recent study also highlighted that separation of the hallux from the second toe characterised the feet of a habitually-unshod Indian population [10] and differentiated them from a habitually-shod- Chinese population. A relationship between Morton’s toe and peak pressure under the first metatarsal head in walking has also been demonstrated, providing support for the assertion that static-foot structure is an important determinant of foot function, specifically, the ability to direct body weight in the sagittal plane in locomotion [20]. More recently, Mei et al [11] demonstrated the importance of an abducted-hallux position in habitually-barefoot participants while running, showing the hallux to share and therefore reduce forefoot loading, possibly due to a wider surface area of support .

Given the mechanical effects of static foot shape, it is worthy of consideration as a mechanism underlying overuse injury in tissues and joints further up the kinetic chain. If force is not appropriately directed in the sagittal plane at the foot, it follows from basic physics that compensations and additional muscular work will have to ensue to counteract unwanted transverse-and frontal-plane motion. The knee joint in particular might be at risk, given its small capacity for non-sagittal-plane movement. Given that walking and running are derived capabilities in humans, and that humans are adapted to perform both activities with minimal energy expenditure [21], it is logical to suggest that a sagittal-plane joint, such as the knee, is best supported with a wide foot that controls and directs the body weight, such that motion at the knee is in the plane for which the joint has evolved.

The effects of footwear on foot structure and function

The plasticity of foot structure was well known and exploited by the Chinese in the ancient cultural practice of footbinding [6,22]. The timescale of structural alterations appears to be rapid, particularly in the young, where bones have yet to fully ossify. Hoffman [6] observed hallux deformation in a habitually-barefoot teenager required to wear shoes for just six weeks. In an adult-case-study patient, Knowles [23] showed reversal of hallux valgus after two years wearing anatomically-shaped shoes (i.e. tip of shoe medial to the medial border of the hallux). Other observational research [7] reported a highly-significant relationship between years of shoe wear and hallux-valgus angle in shoe-wearing communities, with hallux-valgus angle increasing in a linear fashion with years of shoe wear. The observed adaptation of foot structure to shoe wear is in accord with Wolfe’s law, as is the reversal of deformity observed by Knowles [23].

The effect of footwear on foot structure and function will largely depend on the nature of the footwear. The oldest record of footwear dates back some 10000 years [24] with the footwear being a type of sandal. Open sandals have been and continue to be commonly used by hunter-gatherer populations [25]. Such footwear is unlikely to interfere with foot function and shape, but rather simply offers some protection for the plantar surface. In contrast, the highly cushioned, narrow, stiff-soled and toe-sprung footwear characteristic of the modern-running shoe is likely to compromise foot structure and function. Indeed, altered gait patterns, increased maximum impact force, reduced arch deformation and toe flexion have been reported in children running in conventional-running shoes compared to barefoot [26, 27]. Moreover, a comparison of shod and barefoot populations suggested that habitual-western-footwear use leads to stiffer feet with impaired function [28]. There is a dearth of longitudinal studies examining the effects of long-term shoe wear on foot function. A controlled-longitudinal study of the effect of footwear on foot structure and function would be valuable, but is certainly not without methodological challenges. In the absence of such data, the ‘if-you-don’t-use-it-you-lose-it’ principle would suggest that reduced use of the arch and toes would lead to impaired function over time.

The relationship between loss of function and change in foot shape would be of particular interest, but again, previous observational data and simple mechanical principles suggest such a relationship. From an evolutionary perspective, footwear makes sense, particularly given the range of environments in which humans thrive. However, the mechanics and evolution of the foot dictate that such footwear should be anatomically shaped to allow natural-hallux position and function, and also flat and flexible enough to allow unimpeded movement of the foot and toes during locomotion. Such characteristics have been previously recommended [22].

Summary and recommendations

Fundamental physical and mechanical laws and evolutionary biology provide a context to understand structure and function of the human foot, and how both might be compromised by inappropriate footwear. The characteristics that a foot ought to possess to perform load bearing, cushioning and stability roles are observed in the feet of habitually-barefoot populations. Likewise, deformed structure and impaired function have been observed with habitual shoe wear. Future studies on factors related to both performance and injury, and acute-and chronic biomechanical investigations of barefoot-versus-shod running, should attempt to examine data in light of measures of foot structure. Furthermore, care should be exercised in footwear choice, particularly in children, where the effects of conventional footwear on locomotive patterns and foot function have been demonstrated. Interpreting research in light of physical laws and from an evolutionary perspective, might add clarity to a field of investigation that is characterized by equivocal findings.

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