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Case study: Schwannoma of the tibial nerve in a patient with a history of neurofibromas

Posted on September 30, 2019 | Comments Off on Case study: Schwannoma of the tibial nerve in a patient with a history of neurofibromas

by Zachary T. Ritter, DPM, MS, FACFAS1*, Amy Kruger, DPM2

The Foot and Ankle Online Journal 12 (3): 6

A schwannoma is a common benign tumor of the peripheral nerve sheath.  Schwannomas are rarely found in the foot and typically do not elicit any painful symptoms. We report the case of a large schwannoma eliciting tarsal tunnel like symptoms in a patient with a previous history of neurofibromatosis within the spine. The patient had previously undergone lumbar laminectomy for neurofibromas of the lumbar spine that went on to develop pain in the right foot.  She then underwent extensive workup of this persistent right foot pain. She was treated for plantar fasciitis for several years, until presenting to our clinic. At that time, EMG findings showed tibial neuropathy and medial plantar nerve degeneration; accompanied by MRI findings consistent with a schwannoma of the tibial nerve. The patient underwent surgical excision of the mass. The pathology report revealed an encapsulated biphasic tumor composed of compact hypercellular areas and mixed hypocellular areas with foci of hyalinization with no malignant features measuring 3.7 x 2.5 x 2.0 cm, consistent with a diagnosis of schwannoma.  The patient had an uneventful postoperative course. At one year follow up, she was pain free but had persistent neuropathic changes to the distal forefoot. Currently, there are few reports in the literature of schwannomas arising the tibial nerve eliciting the symptoms of tarsal tunnel syndrome. The incidence of such a schwannoma in association of a patient with a history of neurofibromas is even more rare.

Keywords: neuroma, schwannoma, neurofibromatosis, plantar fasciitis

ISSN 1941-6806
doi: 10.3827/faoj.2018.1203.0006

1 – Chief of Podiatric Surgery. UPMC Susquehanna. Williamsport, PA.
2 – PGY-3. St. Luke’s University Hospital. Bethlehem, PA.
* – Corresponding author: ztritter@msn.com

A schwannoma is a benign soft tissue tumor of the peripheral nerve sheath. These slow-growing tumors can be difficult to distinguish from other benign tumors based on clinical findings [1]. The principal diagnosis is made histologically by by identifying the principle cellular elements—Schwann cells. This tumor was first described in the thorax [2], and is typically found in the head, neck, and flexor surfaces of the extremities [3]. The most common nerve affected is the eighth cranial nerve; however, the spinal roots as well as the sympathetic, vagus , ulnar, and peroneal nerves are commonly affected as well [3,4]. This tumor is rarely found in the tibial nerve in the region of the tarsal tunnel [5-9]. Finally it is highly uncommon to find this tumor in association with a neurofibroma, with only one report of a schwannoma of the posterior nerve accompanied by a neurofibroma in the tarsal tunnel itself [10]. There are currently no other reports of a patient with a schwannoma eliciting secondary tarsal tunnel syndrome in a patient with a history of symptomatic neurofibromas elsewhere in the literature.

We report a case of a large schwannoma of the tibial nerve located in the tarsal tunnel in a patient with a previous history of neurofibromas in the spine.

Case Report

A 69-year-old female presented to UPMC Susquehanna Foot and Ankle Clinic in July 2015 with right-sided plantar fascial pain accompanied by plantar foot numbness and tingling.  On clinical exam, her foot was neutrally positioned and demonstrated no clinically palpable abnormality. She did have a positive Tinel and Valleix sign. There was mild tenderness along the plantar fascial ligament origin. The patient had been treated by an outside physician for over 5 years with plantar fasciitis.  She had tried various conservative treatment methods including custom orthotics, physical therapy, and a series of corticosteroid injections, all of which provided only temporary relief. She additionally had a history of a prior lumbar laminectomy secondary to pain, after which she began to notice increasing right foot pain and paresthesias.  Her previous spine MRI (June 2014) revealed extramedullary enhancing masses and nerve sheath tumors leading to a diagnosis of neurofibromas.

During her first visit to our clinic in July 2015, an EMG from the previous month was reviewed.  On EMG, there was evidence of tibial neuropathy and degenerative changes of the medial plantar nerve leading to a diagnosis of tarsal tunnel syndrome.  After her first visit, the patient was recommended an additional course of physical therapy, given a script for new custom orthotics, and prescribed a nonsteroidal anti-inflammatory drug, meloxicam (Mobic). Following this course of treatment, the patient’s symptoms did not improve (Figure 1). An MRI was then ordered of the area which revealed a well-encapsulated oval lesion measuring 4.2 x 2.2 x 2.1 cm, appearing hypointense on T1 and hyperintense on T2 consistent with a diagnosis of schwannoma (Figure 2). 

At this point, surgical excision of the mass was recommended to the patient. An oncology referral was discussed, but deferred until after the procedure in the event that surgical pathology findings did not indicate malignancy. She underwent surgical excision of the mass and decompression of the tarsal tunnel in October 2015. 

Figure 1 Preoperative lateral weight bearing radiograph.

Figure 2 Preoperative MRI T1 and T2 images.

The patient was brought into the operating room and placed on the table in a supine position and general anesthesia was administered. Local anesthesia was then administered to the area utilizing a 1:1 mixture of 1% lidocaine plain and 0.5% bupivacaine plain.  A pneumatic calf tourniquet was applied and inflated.  

Attention was then directed to the medial hindfoot, where a curvilinear incision was made just posterior to the medial malleolus and extended to the medial aspect of the glabrous junction at the level of the porta pedis. The incision was then deepened over the tarsal canal. The flexor retinaculum was then identified and released. Extensive tortuous veins were noted within the tarsal tunnel and were gently mobilized. 

Figure 3 Intraoperative image of the soft tissue mass.

 

Figure 4 Intraoperative specimen of the soft tissue mass after removal from tarsal tunnel.

The tibial nerve was then identified and the proximal portion was mobilized. The dissection was then carried distally exposing a large, swollen tibial nerve just proximal to its bifurcation into the medial and lateral plantar nerves.  

A longitudinal incision was then made in the epineurium and the marginal nerve fibers were mobilized  and retracted in an extra capsular fashion. The tumor was then fully exposed. The plane of the tumor capsule was gently dissected from the epineural layers and the tumor was then separated without significant damage to the surrounding nerve fascicles, though there were several small fascicles noted to be entering the tumor at the distal and proximal poles (Figure 3). These fascicles were isolates in an effort to minimize nerve damage, but due to local ingrowth they were impossible to separate from the tumor and were transected.  

Once the tumor was completely removed, the area was thoroughly flushed with sterile saline solution.  The remaining tibial nerve at the level of the lesion was examined and found to demonstrate significant degenerative changes. As there was no obvious tissue to repair, an amniotic graft was then wrapped around the degenerative portion of the nerve in order to promote healing and prevent adhesions.

The incision was then closed in a layered fashion utilizing monocryl suture for the subcutaneous tissues and nylon suture for skin closure. The operative site was then infiltrated with an additional 10 cc of 1:1 mixture of 1% lidocaine plain 0.5% bupivacaine plain.   The incision was then dressed with xeroform and covered with a dry sterile dressing. A modified Jones compression dressing was then applied. The tourniquet was then deflated and a prompt hyperemic response was noted to all digits. 

The pathology report revealed an encapsulated biphasic tumor composed of compact hypercellular areas and mixed hypocellular areas with foci of hyalinization with no malignant features measuring 3.7 x 2.5 x 2.0 cm, consistent with a diagnosis of schwannoma (Figure 4).

The patient was permitted to immediately weight bear postoperatively in a surgical boot. At two weeks postoperative, she underwent suture removal and was transitioned to a street shoe as tolerated. She was followed until one year postoperatively, and found to have no functional limitations, but did continue to notice sensory changes in the plantar foot. 

Discussion

Schwannomas are benign, encapsulated peripheral nerve sheath tumors. They are commonly described throughout the literature by a variety of names: neurilemoma, neuroschwannoma, peripheral glioma, perifibroma, and schwannoma [11,12]. Typically these tumors are found elsewhere in the body (trunk, head, neck, upper extremities) and even more rarely in the lower extremities [2-3, 13].  The foot is noted only to be affected in approximately 10% of cases [3]. There are even fewer noted in the literature to be associated with the tibial nerve and eliciting tarsal tunnel syndromes [5-9].  

Neurofibromas are not typically found in with the foot and ankle.  In a study by Bakotic and Borkowski of primary soft tissue neoplasms of the foot, schwannomas and neurofibromas were noted to account for only 5.4% and 2.7% of all benign soft tissue tumors, and 2.0% and 1.0% of all total neoplasms respectively in the foot and ankle [14].  It is rarely reported to find these two types of tumors in association with one another, with only one report of a schwannoma associated with a neurofibroma in the tarsal tunnel [10]. 

There are currently no other reports of a patient with a schwannoma eliciting secondary tarsal tunnel syndrome and a history of spinal neurofibromas. Currently the recommended treatment for schwannomas of the foot and ankle is open surgical resection [15]. Fortunately, surgical resection has positive results with minimal morbidity and recurrence if resected entirely [16,17]. It is recommended to remove the lesion in total with great care not to damage the nerve through excessive violation of the nerve sheath or compromising the marginal neural fibers. 

We report a case of successful excision of a schwannoma of the tibial nerve located within the tarsal tunnel, eliciting symptoms leading to a diagnosis of tarsal tunnel secondary to tumor. The patient did have a significant medical history of painful neurofibromas of the lumbar spine confirmed on MRI with a subsequent lumbar laminectomy. While the patient did have EMG findings positive for tibial neuropathy and degeneration of the medial plantar nerve, we cannot effectively determine whether the patient’s symptoms were solely related to compression from the longstanding mass within the tarsal tunnel or if they were possibly exacerbated by the patient’s history of lumbar neurofibromas with subsequent surgical intervention. 

The patient’s postoperative course was uneventful.  She did regain some hindfoot and midfoot sensation, while completely eliminating her preoperative pain.  However, parasthesias persisted within the forefoot. 

References

  1. Graviet S, Sinclair G, Kajani N. Ancient schwannoma of the foot. J Foot Ankle Surg. 1995;34(1):46-50.
  2. Ackerman LV, Taylor FH. Neurogenous tumors within the thorax; a clinicopathological evaluation of forty-eight cases. Cancer. 1951;4(4):669-91.
  3. Odom RD, Overbeek TD, Murdoch DP, Hosch JC. Neurilemoma of the medial plantar nerve: a case report and literature review. J Foot Ankle Surg. 2001;40(2):105-9.
  4. Weiss S, Goldblum J, Folpe AL. Schwannoma. In: Enzinger and Weiss’s Soft Tissue Tumors, ed 5, Elsevier Mosby, Maryland Heights MO, 2008, pp. 853-862
  5. Hallahan K, Vinokur J, Demski S, Faulkner-jones B, Giurini J. Tarsal tunnel syndrome secondary to schwannoma of the posterior tibial nerve. J Foot Ankle Surg. 2014;53(1):79-82.
  6. Grossman MR, Mandracchia VJ, Urbas WM, Mandracchia DM. Neurilemmoma of the posterior tibial nerve with an uncommon case presentation. J Foot Surg. 1992;31(3):219-24.
  7. Mangrulkar VH, Brunetti VA, Gould ES, Howell N. Unusually large pedal schwannoma. J Foot Ankle Surg. 2007;46(5):398-402.
  8. Judd T, Jones T, Thornberry L. Schwannoma of the posterior tibial nerve: case study. J Am Podiatr Med Assoc. 2014;104(5):539-43.
  9. Nawabi DH, Sinisi M. Schwannoma of the posterior tibial nerve: the problem of delay in diagnosis. J Bone Joint Surg Br. 2007;89(6):814-6.
  10. Tladi MJ, Saragas NP, Ferrao PN, Strydom A. Schwannoma and neurofibroma of the posterior tibial nerve presenting as tarsal tunnel syndrome: review of the literature with two case reports. Foot (Edinb). 2017;32:22-26.
  11. White NB. Neurilemomas of the extremities. J Bone Joint Surg Am 49:1605-1610, 1967.
  12. Spiegel PV, Cullivan T, Reiman HM. Neurilemoma of the lower extremity. Foot Ankle 6:194-8, 1986.
  13. Jacobson JM, Felder JM, Pedroso F, Steinberg JS. Plexiform schwannoma of the foot: a review of the literature and case report. J Foot Ankle Surg. 2011;50(1):68-73.
  14. Bakotic BW, Borkowski P. Primary soft-tissue neoplasms of the foot: the clinicopathologic features of 401 cases. J Foot Ankle Surg. 2001;40(1):28-35.
  15. Kellner CP, Sussman E, Bar-david T, Winfree CJ. Schwannomas of the foot and ankle: a technical report. J Foot Ankle Surg. 2014;53(4):505-10.
  16. Carvajal JA, Cuartas E, Qadir R, Levi AD, Temple HT. Peripheral nerve sheath tumors of the foot and ankle. Foot Ankle Int. 2011;32(2):163-7.
  17. Kim DH, Ryu S, Tiel RL, Kline DG. Surgical management and results of 135 tibial nerve lesions at the Louisiana State University Health Sciences Center. Neurosurgery. 2003;53(5):1114-24.

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Longitudinal plantar approach for excision of interdigital perineural fibroma of the foot: A case series and literature review

Posted on March 1, 2016 | Comments Off on Longitudinal plantar approach for excision of interdigital perineural fibroma of the foot: A case series and literature review

by George Flanagan1, Ian Reilly1,2*pdflrg

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

Background:  There is an array of clinically and academically derived opinion as to the correct surgical approach to the intermetatarsal space, most frequently to excise a symptomatic interdigital perineural fibroma (aka Morton’s Neuroma).  The purpose of this retrospective case series was to evaluate the patient outcomes, and sequelae following a longitudinal plantar incision for excision of interdigital perineural fibroma.
Method: This is a retrospective case series of forty-two patients who underwent excision of interdigital perineural fibroma utilizing a longitudinal plantar incision between 2012-2014.  All patients were reviewed at two weeks, four weeks and six months post operatively.  Patient and clinician outcome measures were captured by means of the Manchester-Oxford Foot Questionnaire (MOXFQ) and Patient Satisfaction Questionnaire 10 (PSQ-10).
Results: Forty two patients (forty eight excisions) were assessed both pre operatively and post operatively.  95.2 percent of patients felt their foot was better or much better at six months post operatively.  The average post-operative PSQ-10 score was 85.05 (SD +/- 14.3).  A significant reduction in all three MOXFQ domains was observed.  Four patients had surgical sequelae; only one patient reported no improvement in pain post operatively.  No patients reported worsening symptoms.
Conclusion:  Producing excellent patient outcomes with only minimal complications, this case series substantiates the growing literature showing that excision of interdigital perineural fibroma through a longitudinal plantar incision is both safe and effective.

Key words: interdigital perineural fibroma, soft tissue mass, neuroma, fibroma

ISSN 1941-6806
doi: 10.3827/faoj.2016.0901.0001

1 – Department of Podiatric Surgery, Northamptonshire Healthcare Foundation Trust, England
2 – Private Practice, Northamptonshire, England
* – Correspondence: pod.surgeon@virgin.net

Interdigital perineural fibroma (Morton’s neuroma, interdigital neuroma, Morton’s metatarsalgia) is both a commonly described pathology as well as a frequently encountered affliction.  Although commonly affiliated with Thomas Morton’s description of 1876 (Morton, 1876), of only the third intermetatarsal space, arguably historic precedence can be attributed to either Civinini, (1835), Durlacher, (1845) or Tubby, (1912).

The incidence of interdigital perineural fibroma (IPF) is three-fold in the middle aged female population in comparison to their male counterparts (Naraghi et al, 2014). Symptoms commonly include paroxysmal pain and paresthesia of the pedal web space (most commonly the third) and adjacent digits.  The preferred description of an ‘entrapment neuropathy’ is now frequently utilized (Hassouna & Singh, 2005).  Despite the plethora of literature which exists for this common condition, a continuum of disparity regarding its etiology remains.

Diagnosis is by a thorough mixture of both symptomology and clinical examination.  Musculoskeletal ultrasound and magnetic resonance imaging have been shown to be sensitive diagnostic tools (Sharp et al, 2003).  There exists a treatise of nomenclature relating to this condition.  Although many historic reports entitle IPF as a ‘tumor’, recent histopathologic studies have formalized its histology as a perineural fibroma (Pazzaglia et al, 1996), that of inflammation and fibroblastic proliferation around a nerve.  Despite this, most studies cite an IPF as a benign swelling occurring at the bifurcation of the plantar interdigital nerve.

If symptoms of IPF are refractory despite exhausting conservative treatment modalities, then surgical intervention is indicated (Akermark et al, 2008).  Numerous surgical approaches and procedures have been described for this condition.

Disaccord is prevalent regarding incision placement, particularly whether the incision should be approached dorsally or plantarly (Wilson & Kuwada, 1995).  Evidence does not favor any particular approach to incision, despite this, many practitioners surreptitiously avoid a plantar incision due to concerns surrounding cicatrix, particularly hypertrophic scar formation and intractable plantar keratosis (Hassouna & Singh, 2005).  This case series highlights the method and outcomes relating to patients (n=42) who underwent complete excision of IPF via a longitudinal plantar incision.

Methods

Between 2012-2014 consecutive patients (n=97) who had refractory symptoms despite conservative treatment intervention underwent surgical excision.

Inclusion and exclusion criteria

Of the 97 patients who underwent surgical excision:

Those patients who had surgery performed utilizing a dorsal approach (n=11), patients who had undergone simultaneous bilateral procedures (n=5) and patients who underwent excision in combination with other surgical procedures (n=9) were excluded from the study.  Patients for whom post-operative outcome data was unavailable (n=30) were also excluded.  Patients who had undergone excision of a perineural fibroma unilaterally and in isolation were subsequently included (n=42).  Successive outcome data for at least 6 months was a prerequisite.

Surgical technique

All surgery was undertaken or supervised by the second author (IR).  Patients were all admitted on a day surgery ambulatory basis.  General anesthesia with regional local anesthetic block was used in a minority of patients (4, 9.5%), the majority of patients underwent surgery with regional ‘ankle block’ anesthesia alone.  Standard surgical asepsis and infection control measures were observed.  Surgery took place within a laminar airflow (Howorth Exflow 90) operating theatre.  The procedure was performed utilizing a pneumatic ankle tourniquet set at 80-100 mmHg above the patients’ recorded systolic blood pressure.

A longitudinal plantar incision was made (Figure 1).  The incision extends from the edge of the adjacent web space distally to just beyond the level of the metatarsal heads proximally.  Vessel management was undertaken utilizing bipolar cautery.

Fig1

Figure 1 Plantar longitudinal incision.

Fig2 

Figure 2 Highlighting digital bifurcation.

Fig3

Figure 3 Proximal tracking of nerve.

Fig4

Figure 4 Wound closure.

Utilizing blunt dissection carefully, navigating through the plantar fat pad, the pathological nerve is identified, perineural adhesions were bluntly released ensuring integrity of the surrounding soft tissue architecture.  Visualization and adhesion neurolysis was performed distally at the level of digital bifurcation (Figure 2).

Proximally blunt dissection was undertaken (Figure 3) until normal nerve diameter and visualization was encountered.

The plantar digital nerve was resected distally at its digital bifurcation, and proximally where approximately 10mm of normal nerve had been visualized.  The remaining proximal nerve stump was cauterized and displaced proximally.  Hemostasis was achieved again using bipolar cautery.  The surgical site was then flushed with saline and skin closure achieved with 3-0 monofilament polypropylene suture utilizing a horizontal mattress technique (Figure 4).

Post-operative management

Protocol for post-operative analgesia included co-codamol 30/500 one or two tablets QDS and diclofenac 50mg TDS (PRN).  Co-codamol was replaced for Tramadol 50mg QDS in cases of allergy or intolerance.  All patients were placed in a compression dressing utilizing a universal post-operative shoe (Benefoot) for four weeks, during which time they were allowed to weight bear for essential activities of daily living.  Patients received a wound review at two weeks and removal of sutures at four weeks.  Patients were seen finally for six month review.

Data capture and statistics

Patient reported outcome measures were recorded using paper questionnaires both pre-operatively on the day of surgery and post operatively at 6 month review.  Pre and post operatively patients were asked to complete the Manchester-Oxford Foot Questionnaire (MOXFQ) (Dawson et al, 2006) and post-operatively. In addition to the MOXFQ, patients completed The Patient Satisfaction Questionnaire 10 (PSQ-10) (Rudge & Tollafield, 2003).  Data was inputted electronically to the Podiatric Audit of Surgery and Clinical Outcome Measure (PASCOM-10) system.  During post-operative review clinician determined outcome data was also collected.

Statistics and calculations were achieved using Microsoft Excel (2010 Microsoft Corporation).

Results

Of the patients included in the study (n=42), 33 (78.5%) were female with a mean age of 52.9 (SD +/- 11.8) years (range 28-72) and 9 (21.5%) were male with a mean age of 54.8 (SD +/- 12.8) years (range 44-72).  In 25 (59.5%) cases the left foot was involved, leaving 17 (40.5%) incorporating the right foot.  Neuromas were excised in isolation in 20 (47.6%) cases from the 3rd intermetatarsal space and 16 (38.1%) from the 2nd intermetatarsal space, 6 (14.3%) cases involved both the 2nd and 3rd intermetatarsal space.  Histological confirmation of perineural fibroma was obtained in all samples excised, totaling 48 from 42 feet. (Example of excised sample sent to histology seen in Figure 5).

Fig5

Figure 5 Excised interdigital perineural fibroma.

Of the 42 patients in the study, 4 cases of surgical sequelae were recorded.  Sequelae were recorded during post-operative visits by the attending clinician utilizing electronic data capture. Of the 4 patients, 2 patients (4.7%) suffered with scar line hypertrophy, one patient required surgical revision of the scar with good long term results at six month follow up.  One patient (2.4%) had a suspected stump neuroma at 6 months post op, this patient achieved asymptomatic longevity with one infiltration of 40mg Depo-Medrone, subsequently not requiring further surgery. One patient (2.4%) had a suspected (not proven) superficial infection treated with a 7 day course of antibiotics with no long term negative effect.

Patient satisfaction was captured utilizing the PSQ10.  At 6 months post-surgery 40 (95.2%) patients felt that their foot was better or much better than compared to the original problem.  One patient (2.4%) noted that their foot felt ‘the same’ when compared to the original problem, it was this patient who subsequently required revision of hypertrophic scar formation.  One patient (2.4%) did not state how they felt.  When asked ‘would you have surgery again under the same circumstances?’, 40 (95.2%) said yes and 2 (4.8%) said no.  The majority of patients (13, 31%) were back into preferred footwear by 8 weeks, 2 patients (4.8%) by 2 weeks; 10 (21.4%) by 4 weeks; 12 (28.6%) by 6 weeks with 6 (14.3%) patients waiting until 6 months until they were normally shod.   The average PSQ10 score was 85.05 (SD +/- 14.3).

Figure 6 illustrates the MOXFQ score distribution across the 3 patient reported outcome domains.  In the walking / standing (WS) domain the average pretreatment score was 68.8 (SD +/- 21.5), the post treatment score reduced to 23.1 (SD +/- 27.4).  For social interaction (SI) scores reduced from 51.3 (SD +/- 22.3) to 14.4 (SD +/- 19.5) and in the pain (P) category, 67.1 (SD +/- 18) and 24.6 (SD +/- 22.3) respectively.  Scores in each domain exceeded the threshold (WS 12.8, SI 20.3 and P 4.6) for a clinically significant difference as defined by Dawson et al, (2007).

Fig6

Figure 6 Pre/post op comparative MOXFQ distribution.

Discussion

Interdigital perineural fibroma are a common clinical entity, despite this, there remains disparity both academically and subjectively about its etiology, pathophysiology and long term treatment.  However it is uniformly agreed that surgical intervention is required once conservative treatment has failed (Akermark et al 2013).  Despite this surgical consensus and the vast amount of literature pertaining to it there remains druthers amongst surgeons regarding the surgical approach which should be taken.

Numerous approaches to the intermetatarsal space have been described in the literature, including minimally invasive techniques (Zelent at al 2007). Minimally invasive surgical approaches to excision of IPF have been available for a number of years (Barrett & Pignetti, 1996), however such approaches are often utilized when performing procedures alternative to excision of the pathological nerve such as decompression of the deep intermetatarsal ligament (Dellon, 1992).  Excision of the fibrosed nerve in toto is the most common procedure of choice (Jain & Mannan, 2013), for this, four main approaches to the intermetatarsal space have been described, which include; the longitudinal plantar, transverse plantar, web space approach and longitudinal dorsal.

Patient satisfaction has shown to be high following IPF excision (Thomson et al, 2004).  Despite this, reports state satisfaction rates as low as 65% (Nashi et al, 1997) and as high as 100% (Colgrove et al, 2000) utilizing various surgical approaches and methods.  As such Thomson’s Cochrane review (Thomson et al, 2004) concluded that there was insufficient evidence to assess formally the effectiveness of both operative and conservative treatment for IPF.  Further appraisal of the literature also shows discourse on failure rates following surgical intervention, ranging from 3% (Giannini et al, 2004) to as high as 24% (Younger & Claridge, 1998).

Akermark et al (2013) performed one of the first prospective randomized controlled trials providing comparative data for dorsal vs longitudinal plantar approaches to excision of IPF.  Patient satisfaction and pain reduction were comparable between both groups.  A reduction in daily activity restriction was noted in both dorsal and plantar groups, 67% and 77% respectively.  Pain reduction was 96% in the plantar incision group and 97% in the dorsal group. Other studies citing similar satisfaction rates are available.  Akermark et al, (2008) in an earlier study found 86% satisfaction rates following plantar incision, Jerosch et al, (2006) showed 92% satisfaction following longitudinal plantar incision.  Wilson & Kuwada, (1995) in a 15 year follow up study of 29 patients (59 neuromas) found preference for the plantar transverse incision when compared to a dorsal incision, with 68% satisfaction rate following dorsal incision and 100% satisfaction in the plantar approach group.  Barbosa et al, (2005) & Nery et al, (2012) also advocated a plantar transverse incision reporting 89.5% and 89.4% satisfaction respectively. Similar favorable data exists for surgery performed utilizing a longitudinal dorsal incision.  Lee et al, (2011) followed patients over 10 years, 61.4% of patients were completely satisfied, however they broke down a further 38% that were satisfied with reservations, totaling an overall 99.4% satisfaction rate.

Coughlin & Pinsonneault, (2001) using a median follow up of sixty nine months found patient satisfaction high at 84% of 66 patients (74 neuromas), good / excellent results were also compiled into satisfaction rates in studies by Giannini et al, (2004) and Kasparek & Schneider, (2013) citing 77% and 76.5% respectively.  Whilst no significant difference has been concluded in the literature, particularly that comparing multiple surgical approaches (for which there are few) patient satisfaction does seem to be slightly higher in those studies utilizing the plantar incision (both longitudinal and transverse).  Two very recent studies are also showing high patient satisfaction rates following the plantar approach (Killen et al, 2015 & Kundert et al 2015), this study adds to that data, showing a patient satisfaction rate of 95.2%.  Despite there being no significant difference in patient outcomes with either approach, as noted previously in this article, there seems to be a subjective preference for dorsal incision due to concerns regarding surgical sequelae (McKeever, 1952).

Whilst concern is derived from the notion of increased risk of intractable plantar keratosis and hypertrophic scarring following a plantar approach to excision of IPF, there remains a multitude of literature showing relatively comparable rates of surgical sequelae for both dorsal and plantar approaches.  Akermark et al, (2013) studied 97 patients and found 5 complications following IPF excision through a plantar incision and 6 through a dorsal incision.  Of the plantar group three cases of small ‘pea sized’ hypertrophic scar formation and one large hypertrophic scar were noted, all were revised with superficial excision and included in the final satisfaction results.  Of the 6 complications from the dorsal group these included one resected artery as oppose to IPF (confirmed by histology), one infection, one dehiscence, one deep vein thrombosis and two patients with recalcitrant pain requiring revision surgery through a plantar incision.  Patients reported sensory loss 85% of the time in the dorsal group compared to 66% in the plantar group.  Jerosch et al, 2006 noted 2.8% of patients with problematic scars and 1.7% infection in a large cohort of 356 patients.  Barbosa et al, 2005 found one patient of a nineteen cohort to have dehiscence, with no further complications cited.  Kundert et al, 2015 in a midterm follow up study also found favorable scar sequelae with a 5.3% symptomatic scar rate in 51 feet.  Like Akermark et al, (2013), Wilson & Kuwada, (1995) compared complication rates between both dorsal and plantar approaches, in a 15 year follow up they found a 6.7% complication rate for plantar incision and a 17% complication rate for the dorsal approach.

Similar to Akermark et al, (2013) the plantar group had two cases of problematic scar formation; however, this mirrored the dorsal group who also reported two patients with pathological scar formation.  In addition to the two patients suffering with scar tenderness, the dorsal group also had six reported cases of recurrent neuroma, one hematoma and one deep vein thrombosis.  Nery et al, (2012) found a lower incidence of complication compared to other studies (6.9% patients reported a ‘fair result’), however unlike other studies focusing on plantar incisions they had a 3.8% stump re-occurrence, confirmed via histology following revisional surgery.  Studies focusing on the longitudinal dorsal approach show no significant difference in complication rates when compared to plantar incision, however the specific type of surgical sequelae differs with approach.  Lee et al, (2011), Wilson & Kawada, (1995) and Akermark et al, (2013) all report significant discomfort related to sensory loss following IPF excision through a dorsal approach with two of these studies directly comparing dorsal and plantar incisions.  The results of the two studies (Wilson & Kuwada, (1995) & Akermark et al, 2013) which directly compare multiple surgical approaches have already shown the surfeit of sequelae which may arise following a dorsal approach, in addition to this, Coughlin & Pinsonneault, (2001) also found problems related to ‘uncomfortable’ paresthesia post operatively as well as six superficial infections, one deep infection, a case of complex regional pain syndrome and adjacent metatarsophalangeal joint instability.  In this case series the complication rate deduced was 9.6% (4 patients) which averaged between the literature scrutinized, however given the small sample size an elevated complication percentage is expected.  Of the four patients with complications, two patients had satisfactory outcomes, one patient chose not to comment and one patient (2.4%) was deemed to have a failed outcome; ultimately culminating in a 95.2% satisfaction rate.

Conclusion

Whilst we have shown that there is a risk of cicatrix’s following surgery approached through the plantar surface of the foot, research infers that there is no evidence to suggest inferior patient outcomes following this approach, particularly when compared to alternative surgical approaches.  In fact the risk of adverse scarring following this approach is comparable with data derived from cohorts utilizing a dorsal incision, thus negating the argument of mechanically induced scar hypertrophy.  In fact an interesting outcome of the Coughlin & Pinsonneault, (2001) study was the 15% incidence of post-operative intractable plantar keratosis development around an adjacent metatarsophalangeal joint following a dorsal incision. This could be a potential side effect of division of the deep intermetatarsal ligament, which requires further research in the future.

This case series produced excellent patient outcomes, in common with recent literature; a significant reduction in pain with increased mobility and social inclusion.  The existing literature already justifies the longitudinal plantar approach to excision of intermetatarsal perineural fibroma, showing a low (and less varied) complication rate: this case series substantiates this.

References

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