The Foot and Ankle Online Journal 3 (3): 2
Introduction: Ankle equinus is a hereditary or acquired contracture of the triceps surae or shortening of the connective tissue causing inability of the foot to dorsiflex during gait. For the patient population with diabetes mellitus, this high plantar pressure from contracture often results in ulceration. This is frequently treated by Achilles tendon lengthening which helps to avoid infection and amputation. The purpose of this study is to examine the effect of dynamic splinting in reduction of ankle equinus contracture for patients with diabetes mellitus.
Methods: A retrospective analysis was accomplished by reviewing the history of 48 patients following treatment with an ankle dorsiflexion dynamic splint. This dynamic splinting modality delivers low-load prolonged duration stretching while one sleeps. In this home therapy study, dynamic splinting was used for a mean 240 hours in the first month (5 weeks).
Results: Patients showed a statistically significant change in maximal ankle dorsiflexion (P < 0.0001). The patients mean, maximal active range of motion in dorsiflexion increased by 9º in the first month.
Conclusion: This modality proved effective as home therapy and should be examined in further research so that it may be employed as standard of care in treating ankle equinus contracture.
Key words: Bilateral tension, Dynasplint, Home therapy, Rehabilitation.
Accepted: February, 2010
Published: March, 2010
Ankle equinus is defined as the failure to achieve 10° of dorsiflexion during the gait cycle. [1-10] This disability is the result of contracture and has a significant prevalence in patients who have also been diagnosed with Diabetes Mellitus (DM), both Type 1 and Type 2. [1-4]
Contracture by definition is the molecular shortening of connective tissue and is considered to be the underlying cause of this equinus. [2,3] Contracture of connective tissue is also evident in other pathologies causing other limitations in active range of motion (AROM). [13-19]
Diabetic neuropathy is an underlying neurological condition of ankle equinus contracture when the peroneal nerve is involved. Peroneal nerve atrophy allows the posterior muscle group to overpower the weakened anterior muscles. 
In addition, plantar nerve neuropraxia or neurotemesis affecting the posterior tibial nerve (medial and lateral plantar nerves) causes a severe muscle imbalance between the larger and more powerful leg muscles and the intrinsic foot muscles. This contributes to the Lisfranc’s dislocation typically seen in the Charcot diabetic foot. This is similar to the neuromuscular hypertonicity following a stroke which is commonly treated with Botulinium Toxin-A (tone management) and dynamic splinting (for contracture reduction). 
A study by Van Gils and Roeder showed the incidence of equinus deformity was present in 91% of patients with DM (n = 151, ages 51-95),1 and a study of 1,666 DM patients by Lavery, et. al., showed 50.3% incidence of ankle equinus (All male; mean age 69 +/- 11 years).  National estimates from the American Diabetes Association list the current population of both diagnosed and undiagnosed DM to be 23.7 million Americans and the current “Diabetes-related spending” is $133 billion dollars in the USA. 
The current standard of care in treating ankle equinus includes shoe modification,1 ankle mobilization therapy including passive stretching [1-4] and surgery (Achilles tendon lengthening, gastrocnemius recession, or tendon advancement procedures). [1,5,6,11]
The goal of all of these treatments is to prevent the need for amputation following uncontrollable infection from ulceration. The purpose of this study is to examine the effect of dynamic splinting in reduction of ankle equinus contracture for patients with DM.
The Ankle Dorsiflexion Dynasplint® (AFD) (Dynasplint Systems, Inc., Maryland, USA) achieves a low-load, prolonged stretch to reduce contracture through increased time at end range (of motion). [13-19] The Dynasplint® units are worn at night (for 6-8 hours of continuous wear) while sleeping. The Dynasplint® modality has bilateral tension rods that allow for a tissue specific stretch. The device permits dynamic tension settings to be changed, which allow tension to be increased as the end range progresses and the deformity is reduced The AFD used in this study has been shown effective for treating excessive plantar flexion in stroke patients  and has shown similar efficacy for treating other conditions requiring contracture reduction. [14-19]
Records of patients with diagnosed ankle equinus, secondary to DM were used for this retrospective study. Patients’ records who were treated with AFD were retrieved from multiple ankle and foot clinics in Georgia, Texas, and California. Maximal ankle dorsiflexion measurements were the dependent variable and these measurements taken with goniometry while the patient was lying supine with the knee fully extended. The 48 enrolled patients included 25 females and 23 males (mean age of 66 ± Standard deviation 11). The ethnic distribution included 7 African Americans, 4 Asians, 27 Caucasians, and 10 Hispanic patients.
Patients’ initial introduction to the AFD, included customized fitting with consideration for the patient’s foot size and varying degrees of edema which may be present. Patient training was instituted by the technician trained on the Dynasplint systems. Verbal and written instructions were provided throughout the duration of treatment for safety, general wear and care, and tension setting goals based on patient tolerance. (Fig. 1)
Figure 1 Ankle Dorsiflexion Dynasplint®.
Each patient was instructed to start by wearing the AFD for a few hours before sleeping for one day, and then for 6-8 hours while sleeping using an initial tension setting of #1 (2.0 foot pound of torque). This initial frequency, intensity, and duration are used for patient acclimatization to the system. The patients were then instructed to increase the tension one increment every two weeks as tolerated. If the new tension gave the patient “prolonged soreness or pain” (defined as greater soreness than would occur after one hour of intense manual therapy), the patient was instructed to reduce the tension one half increment for a few days before returning to the new setting.
The duration for this study was five weeks. This period was selected to ensure 100% patient compliance and to avoid what one study reported as “difficult (prolonged) follow up.”  However the AFD is routinely prescribed for six or more months in treating this condition.
A paired t-test was calculated to determine if a statistically significant difference existed between the initial, maximal AROM and the final, maximal AROM. The calculations were done independently by an outside biostatistician, Dr Ram Shanmugam from Texas State University, San Marcos, TX.
There was a statistically significant difference in the pre vs. post measurements of patients’ maximal, AROM in dorsiflexion, (p< 0.0001, t = 6.469, df = 47, n = 48). The mean improvement was 20% in just one month. (Fig. 2)
Figure 2 Mean change in active range of motion.
The purpose of this study is to examine the effect of dynamic splinting in reduction of ankle equinus contracture for patients with diabetes mellitus. Burke, et al., described hypomobility and diabetic ulcers saying “plantar-flexed first ray deformity (contracture) has been shown to increase pressure on the first metatarsal head and is associated with ulceration.”  The AFD used in this trial reduced contracture using passive stretching similar to one component used in the study by Danaberg, et al. The Danaberg study included manual therapy “Mobilization” and passive stretching or “assisted stretching”. The findings show an instant 4.9º improvement in maximal dorsiflexion.  Comparable passive stretching was delivered by the AFD but for substantially longer durations as it was worn for 6-8 hours wear during sleep. The AFD wear averaged 6.9 hours per night equaling a total of 241 hours of end range stretching. AROM measurements were taken several hours after awakening which showed stable improvement in contracture reduction.
Literature has shown a direct relationship between mechanical stress (positioning), foot ulceration, and surgery. [3,4,9] Research has also described connective tissue elongation from prolonged stretching  and sarcomere changes from limb lengthening.  The current standard of care, surgical resolution of ankle equinus contracture, has been established. [1-12] However, use of a modality like the AFD could prevent the need for surgery in a significant number of patients. A previous protocol of using serial casting has been discontinued for DM patients due to the great frequency of skin breakdown and ulcerations from the casting itself. There were no incidences of skin breakdown reported in this retrospective AFD study.
The limitations on this study include lack of a control group, but this study did have high external validity due to the retrospective design which recruited patient records completed before initialization of the study.  The study was also limited by its short duration. However, the study by Danaberg, et al., described that a shorter duration study was more likely to display results from the highest patient compliance. This five week study had 100% compliance in wear and tracking of this modality. 
Use of the biomechanically correct AFD® with bilateral, dynamic tension has proven effective in this study achieving a mean 9º increase in maximal, active range of motion in one month. This treatment method of dynamic splinting as a home therapy should be considered before surgery is implemented to reduce ankle equinus contracture. In addition, awareness by the physician of these potential damaging equinus factors would suggest early and immediate use of the device for prophylaxis. The normal prescription of this system is six months. A future experiment measuring changes from six month duration in a randomized, controlled trial would prove the efficacy of this modality.
1. Van Gils CC, Roeder B. The effect of ankle equinus upon the diabetic foot. Clin Pod Med Surg 2002 Jul; 19(3): 391-409.
2. Lavery LA, Armstrong DG, Boulton AJM. Ankle equinus deformity and its relationship to high plantar pressure in a large population with diabetes mellitus. JAPMA 2002 92: 479-482.
3. Frykberg RG. The high risk foot in diabetes mellitus. New York: Churchill Livingstone, 1991.
4. Dananberg HJ, Shearstone J, Guillano M. Manipulation method for the treatment of ankle equinus. JAPMA 2000 90: 385-389.
5. Birke JA, Patout CA, Foto JG. Factors associated with ulceration and amputation in the neuropathic foot. JOSPT 2000 30(2): 91-97.
6. Menz HB, Dananberg HJ. Manipulation method for the treatment of ankle equinus. JAPMA 2001 91: 105-106.
7. Wallny T, Brackmann H, Kraft C, Nicolay C, Pennekamp P. Achilles tendon lengthening for ankle equinus deformity in hemophiliacs: 23 patients followed for 1-24 years. Acta Orthop 2006 Feb;77(1):164-168.
8. Grady JF, Saxena A. Effects of stretching the gastrocnemius muscle. J Foot Surg 1991 Sep-Oct; 30(5): 465-469.
9. Bowers AL, Castro MD. The mechanics behind the image: foot and ankle pathology associated with gastrocnemius contracture. Semin Musculoskelet Radiol 2007 Mar; 11(1): 83-90.
10. Mullaney MJ, McHugh MP, Tyler TF, Nicholas SJ, Lee SJ. Weakness in end-range plantar flexion after Achilles tendon repair. Am J Sports Med 2006 Jul; 34(7): 1120-1125.
11. Chen L, Greisberg J. Achilles lengthening procedures. Foot Ankle Clin 2009 Dec; 14(4): 627-637.
12. Orendurff MS, Rohr ES, Sangeorzan BJ, Weaver K, Czerniecki JM. An equinus deformity of the ankle accounts for only a small amount of the increased forefoot plantar pressure in patients with diabetes. JBJS 2006 Jan; 88B (1): 65-68.
13. Lai J, Jones M, Willis B. Effect of Dynamic splinting on excessive plantar flexion tone/contracture: A controlled, cross-over study. Proceedings of the 16th European Congress of Physical and Rehabilitation Medicine. Minerva Medica pubs, Italy. 2008 August: 106-109.
14. John MM, Willis FB, Portillo A. Runner’s hallux rigidus reduction and gait analysis, JAPMA 2009 99(4): 367-370.
15. Lundequam P, Willis FB. Dynamic splinting as home therapy for toe walking: A case report. Cases J 2009 Nov 2: 188.
16. Willis FB, John MM, Perez A. Plantar fasciopathy treated with dynamic splinting. PM&R 2009 Sep 1; 9: S169.
17. Sheridan L, Lopez AL, Perez A, John MM, Willis FB. Plantar fasciopathy treated with dynamic splinting: A randomized controlled trial. JAPMA In press.
18. John MM, Kalish SR, Perns SV, Willis, FB. Dynamic splinting for hallux limitus: A randomized controlled trial. JAPMA. In press.
19. Kalish SA, Willis FB. Hallux limitus and dynamic splinting: a retrospective series. The Foot & Ankle Online Journal 2009 Apr; 2 (4): 1.
20. Huang ES, Basu A, O’Grady M, Capretta CJ. Projecting the future diabetes population size and related costs for the U.S. Diabetes Care 2009 Dec; 32 (12): 2225-2229.
21. Kooistra B, Dijkman B, Einhorn TA, Bhandari M. How to design a good case series. JBJS 2009 May; 91A Suppl 3: 21-26.
22. Usuba M, Akai M, Shirasaki Y, Miyakawa S. Experimental joint contracture correction with low torque-long duration repeated stretching. Clin Orthop Relat Res 2007 Mar; 456: 70-78.
23. Makarov M, Birch J, Samchukov M. The role of variable muscle adaptation to limb lengthening in the development of joint contractures: an experimental study in the goat. J Pediatr Orthop 2009 Mar; 29(2):175-181.
Address correspondence to: F. Buck Willis, PhD University of Phoenix: Axia College, Adjunct Professor of Health Sciences, and Dynasplint Systems, Inc. PO Box 1735 San Marcos TX 78667 (512) 297-1833
1 Podiatry; Ft Worth, Texas 910 W North Side Dr Ft Worth, TX 76164. (817) 625-1103 .
2 Atlanta Foot and Leg Clinic, P.A. 6911 Tara Blvd #A Jonesboro, GA 30236-1548 (770) 477-9535
3 Ankle & Foot Centers 2790 Sandy Point Rd. #300 Marietta, GA 30066 (770) 977-3668
4 University of Phoenix: Axia College, Adjunct Professor of Health Sciences, and Dynasplint Systems, Inc. PO Box 1735 San Marcos TX 78667 (512) 297-1833
© The Foot and Ankle Online Journal, 2010