16 Revision Intermetatarsal Neurectomy Abstract Interdigital neuromas are a common cause of forefoot pain. Recurrent or persistent symptoms are common after primary excision and may lead to significant impairment. Failure of initial excision may result from incorrect diagnosis, inadequate excision, or formation of a stump neuroma. Symptoms usually recur within the first 12 months. History and physical examination are the mainstays of diagnosis. Corticosteroid injection may be beneficial but should be limited. Conservative treatment is usually warranted but there is a high failure rate. Results of revision intermetatarsal neurectomy are satisfactory but less gratifying than those of primary excision. Keywords: interdigital neuroma, recurrent, metatarsalgia, Morton’s neuroma, forefoot, surgical treatment, nerve transposition • Approach revision intermetatarsal neuroma surgery with circumspection. • Presumed recurrence may be due to previous wrong diagnosis, inadequate resection, or inadequate preparation and placement of nerve trunk following resection.1–4 • Histologic changes in a primary interdigital neuroma occur distal to the transverse intermetatarsal ligament and represent an entrapment neuropathy resulting in perineural fibrosis.5,6 • Recurrence following interdigital neuroma resection represents a true histopathologic stump neuroma (haphazard proliferation of axions)6 (Fig. 16.1). • Stump (true) neuromas tend to form at the transected end of nerves, and proliferation is directed toward the skin or distal portion of the transected nerve.7,8 • Differential diagnosis includes • Two-thirds of patients present with symptoms of “recurrent” neuroma within 12 months of index surgery.2 This probably represents an original misdiagnosis or resection of the wrong structure or original inadequate resection.9,10 • An incisional neuroma of a branch of the superficial peroneal nerve may occur and will result in primarily dorsal pain. • It is important to obtain a thorough, detailed history and physical examination in patients suspected of having a recurrent interdigital neuroma.4,5.11–15 • Those with a stump neuroma often complain of plantar pain (burning, aching, electrical) radiating proximally (unlike an original Morton neuroma in which the pain radiates distally). • Patients often relate the sensation of “walking on a rock” and pain relieved by removing tight shoes and walking on soft surfaces.2 However, unlike an original Morton neuroma in which the symptoms can be quite vague, a true stump neuroma usually results in very localized, reproducible pain. • If the patient denies digital numbness, even in the immediate postoperative period following the index procedure, a true stump neuroma is doubtful. If this history is given, it is necessary to rule out other causes in the differential including original inadequate resection. • Plantar tenderness in the web space is the most common physical examination finding.5,6,11–13 Usually, more localized, reproducible, and intense than with an original Morton neuroma. • Pain is aggravated by ambulation and shoe wear and relieved with rest.2,3,12,14,15 • Patients likely have a positive “Tinel sign,” although the pain often radiates proximally. • Plantar flexion of the corresponding MTP joint can help differentiate joint synovitis from a neuroma. This maneuver causes increased pain with a synovitic joint, but pain is uncommon in patients with a neuroma. • The Mulder test often is useful.5,6,11–14,16 This test is best performed with the patient positioned prone with the knees flexed 90 degrees. Pain often is more pronounced and the “click” less pronounced in patients with recurrent neuromas compared to those with primary Morton neuromas (Fig. 16.2). Fig. 16.1 Recurrence following previous interdigital neuroma resection represents a true histopathologic stump neuroma (haphazard proliferation of axions). Fig. 16.2 Mulder test is useful; however, the “click” is less pronounced in patients with previous neuroma excision. Performing this test with the patient prone has proved useful. • Metatarsal fat-pad atrophy may occur after primary neuroma excision (perhaps due to poor technique), but also may result from aging, trauma, medications, or other conditions. Fat-pad atrophy increases the risk of continued pain after surgery and must be discussed with the patient. • The diagnosis of recurrent intermetatarsal neuroma is primarily a clinical exercise, relying on history and physical examination.2,5,12–14,16 • Standing anteroposterior, lateral, and oblique radiographs are necessary to assess the MTP joint and osseous structures. • Electromyographic nerve conduction studies are rarely useful in diagnosing a recurrent intermetatarsal neuroma, but may be beneficial in cases of suspected concomitant tarsal tunnel syndrome or lumbar radiculopathy.3,10 • In the case of an ambiguous clinical examination, a magnetic resonance imaging (MRI) or ultrasound (US) may help identify conditions such as a stress fracture or a space-occupying lesion causing neuritic pain. US appears more helpful than MRI in the diagnosis of a recurrent neuroma. • However, both of these imaging modalities have a high false-negative rate (approximately 20%), especially for small neuromas.17,18 • Nonoperative treatment results in varying degrees of relief, but only 20 to 30% get complete, lasting resolution of symptoms.12 • Approximately 40% of those treated conservatively experience enough symptomatic relief to avoid surgery. Therefore, nonoperative treatment is recommended before surgical intervention. • Wide, soft inner–soled, stiff, laced shoes with a low heel are recommended.12–14 • An accommodative orthotic with a metatarsal support can be placed proximal to the point of maximal tenderness11,12,14,19 (Fig. 16.3). • A corticosteroid injection may provide symptomatic relief for up to 2 years in approximately 30% of patients2,4,11,20 (Fig. 16.4). • Pain control after surgical intervention is less predictable in patients being treated for chronic pain, diagnosed with a mood disorder, taking preoperative narcotics, or using tobacco products. Obesity has not been associated with worse outcomes.21–23 • A lengthening procedure should be considered in those with a tight gastroc-soleus complex (Silfverskiöld’s test). • Absolute and relative surgical contraindications are the same as for any forefoot surgery, for example, peripheral vascular disease, poorly controlled diabetes mellitus (A1C > 8), and local infection.23 The goal of revision intermetatarsal neurectomy is relief of pain and dysfunction. It must be made clear to the patient that intermetatarsal neurectomy is more unpredictable in terms of
16.1 Indications
Distal resection of previous neuroma.
Failure to excise correct structure (e.g., lumbrical).
Adjacent web space neuroma.
Metatarsophalangeal (MTP) joint synovitis.
Freiberg osteochondrosis.
Stress fracture of the metatarsal neck.
Tarsal tunnel syndrome.
Peripheral neuropathy.
Lumbar radiculopathy.
Unrelated soft-tissue tumor (e.g., ganglion, synovial cyst, lipoma).
16.1.1 Clinical Evaluation of Pathology (History)
16.1.2 Clinical Evaluation of Pathology (Physical)
16.1.3 Radiographic Evaluation
16.1.4 Nonoperative Options
This injection can be both diagnostic and therapeutic; however, caution is required to ensure the medication is placed around the neuroma (not intraneural) and the MTP joint is avoided.
US guidance may help direct the injection and document appropriate placement.
Injections should be attempted with caution given fat-pad atrophy, skin discoloration, or MTP joint instability may occur.
No more than two injections should be attempted.
We use a mixture of 40-mg Depo-Medrol:1-mL 0.25% Marcaine and a dorsal approach for the injection.
16.1.5 Contraindications
16.2 Goals of Surgical Procedure
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