Surgery for Morton Neuroma Treatment & Management

Updated: May 28, 2019
  • Author: Lyle T Jackson, MD; Chief Editor: Vinod K Panchbhavi, MD, FACS  more...
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Treatment

Approach Considerations

The indication for surgery is significant pain or dysfunction that is not tolerated by the patient and that fails to respond to conservative management.

Once the diagnosis is made and conservative management has failed, few contraindications for surgical intervention exist. Local soft-tissue factors, such as infections or vascular insufficiency, are likely to be the only absolute contraindications. Patient psychosocial issues may be relative contraindications and must be addressed prior to surgical procedures of any kind.

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Medical Therapy

The biomechanical goals of nonsurgical management are to reduce forefoot compression and to eliminate the effect of intermetatarsal ligament tension. In theory, this decreases the overall pressure on the nerve and allows it to function more normally. Shoe modifications are simple to understand but may be objectionable to some patients. Wide toe-box shoes are preferred to relieve pressure across the metatarsal heads. High-heeled and narrow shoes should be avoided. The use of a metatarsal pad orthotic device can help keep pressure off the nerve. [31]

The literature is conflicting regarding the success rate for nonsurgical management, but a reasonable estimate would be that 20-30% of patients would obtain either total resolution of symptoms or improvement to a satisfactory level with footwear modifications and restrictions. [32]

Corticosteroid or local anesthetic injections may be helpful, especially when coupled with the aforementioned shoe modifications. A dorsal injection is administered with 40 mg of methylprednisolone or a similar corticosteroid and 1% plain lidocaine or 0.5% plain bupivacaine in the same syringe. To avoid steroid-induced skin necrosis, do not inject into the superficial subcutaneous tissue. Ultrasound-guided injections are likely to yield better results than blind injections. [33]

Injections should not be used indiscriminately, because the injection itself is associated with mild risk. High-quality evidence supports the use of corticosteroid injections for short-term (3-month) symptom relief. [34, 35] Symptom relief may last longer in smaller neuromas (< 5 mm). [35]

Alcohol sclerosing injections should be used with caution, in that they have not been shown to be reliably effective. [36, 37, 38, 39]

Nonsteroidal anti-inflammatory drugs (NSAIDs) or antiseizure medications such as gabapentin or pregabalin (off label) have been used for symptom management, but their efficacy is not known. [4]

A study by Masala et al (N = 52) found percutaneous radiofrequency ablation (RFA) to be a safe, efficient, and minimally invasive technique for the treatment of symptomatic Morton neuroma. [40]

 

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Surgical Therapy

Plantar vs dorsal approach

Current surgical care for Morton neuroma involves a few different options for either decompressing or resecting the nerve. [41, 42] The first consideration relates to the choice of surgical approach: plantar or dorsal. The dorsal approach has the advantage of low wound complications, lower incidence of plantar scar formation, and immediate weightbearing. The plantar approach is more direct, requiring less dissection, and preserves the transverse metatarsal ligament, theoretically reducing metatarsal instability.

A randomized controlled trial comparing dorsal and plantar approaches showed similar clinical outcomes and rates of complications between the two, but with different types of complications occurring in each group. [43] The plantar group most commonly had minor hypertrophic scar–related complications, whereas the dorsal group's complications were varied. A single retrospective review from the same author also found the two approaches to be comparable. [44]

A study by Habashy et al that compared plantar (n = 17) and dorsal (n = 20) approaches to neurectomy found no statistically significant differences between the dorsal- and plantar- approach groups with regard to outcomes and patient satisfaction. [45]

The plantar approach is through a 3- to 4-cm transverse incision centered over the neuroma on the distal metatarsal fat pad and away from the weightbearing area. [8] This approach provides direct exposure of the nerve, which lies plantar to the intermetatarsal ligament. Alternatively, a longitudinal incision can be made in the interspace. Weightbearing is not recommended until the sutures are removed (2-3 weeks). (See the images below.)

Distal plantar transverse incision. Distal plantar transverse incision.
Plantar longitudinal incision. Plantar longitudinal incision.

The dorsal approach is through a similar-sized (3-cm) longitudinal incision centered on the metatarsal head interspace. [46, 7] A small Inge retractor or laminar spreader is used to widen the intermetatarsal space and apply tension to the transverse metatarsal ligament. The ligament is then transected. The neuroma can then be identified. This approach allows immediate postoperative weightbearing. (See the images below.)

Dorsal incision. Dorsal incision.
Superficial exposure. Superficial exposure.

Regardless of the approach, it is prudent to inspect the area carefully to look for concurrent pathology (eg, lipomas, osteophytes, or inflamed bursae). Care must also be taken to preserve the digital vascular structures.

Choice of definitive operation

After the decision is made as to which approach to use, the definitive surgical procedure must be performed—another somewhat controversial issue.

One option is simply to divide the intermetatarsal ligament and thereby decompress the intermetatarsal space. This decompression may be coupled with neurolysis, depending on the surgeon's preference. Proponents of this option generally believe that decreasing the stresses on the nerve is the key to successful treatment and that if the nerve is preserved, some normal nerve function can return. Furthermore, if no nerve tissue is resected, there is no chance that a recurrent (stump) neuroma will form. A deep transverse metatarsal ligament release combined with a metatarsal-shortening osteotomy has been shown to yield better outcomes than release alone. [47]

A second option is to perform a neurectomy (see the images below). Proponents of this approach believe that the key to successful treatment is eliminating the pathologic nerve tissue and maintain that decompression would only decrease the ongoing mechanical stresses on that abnormally functioning nerve. It is very important to transect the nerve as far proximal to the bifurcation as possible. Multiple authors promote transecting the nerve 3 cm proximal to the proximal border of the intermetatarsal ligament; this allows proper resection of the plantar branches that may otherwise prevent nerve stump retraction away from the weightbearing surface. [7, 48]

Deeper dissection. Deeper dissection.
Neuroma and adherent fibrofatty tissue. Neuroma and adherent fibrofatty tissue.

A third option is a transposition of the cut digital nerve. In this case, the digital nerve is transected sharply distal to the bifurcation. The common digital nerve is then dissected free and transposed into the interval between the transverse head of the adductor hallucis and the interossei muscles. [9]

Ratanshi et al retrospectively assessed neuroma excision with interpositional nerve grafting as a therapeutic option for Morton neuroma in eight patients (nine neuromas) in whom nonoperative therapy had failed. [49]  Patients were followed for at least 1 year after the procedure. When last seen, all eight patients reported improvement in their pain, and no neuroma recurrences had developed. Seven of the eight regained sensation in the grafted hemitoe, and all eight resumed full weightbearing. There were no major complications associated with the procedure; however, one patient experienced wound dehiscence secondary to hematoma.

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Postoperative Care

Postoperative care depends on the surgical approach. For the dorsal approach, the patient begins weightbearing as tolerated in a postoperative hard-soled shoe, with gradual introduction of appropriate footwear as tolerated once the wound has healed and swelling has resolved. For the plantar approach, weightbearing is restricted to the heel only until the incision heals, so as to prevent plantar wound complications.

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Complications

An expected complication of the neurectomy is loss of cutaneous sensation of the interdigital skin. For most patients, this is not clinically significant. A variable amount of numbness may be present on the plantar skin, just proximal to the web space. Some authors believe that this can be more problematic and thus may be more likely to perform surgical decompression of the nerve (and not resect it) to avoid this complication. [2]

In the rare cases where simultaneous adjacent neurectomies have been performed, the toe is affected by a more dense numbness from the metatarsal head to the tip of the digit. One study showed that this increased numbness caused some awkwardness with nail care but no significant disability. [50]

Intractable plantar keratosis underneath adjacent metatarsal heads has been identified as a potential complication, likely as a result of weightbearing mechanics that were altered by releasing the intermetatarsal ligament. [7] Wound complications are typically minor when they occur. Antibiotic treatment or debridement may be indicated.

Recurrent or persisting symptoms after surgical intervention may relate to a number of factors and can be difficult to treat. Patients who have had the decompression type of procedure may continue to have problems if the decompression was incomplete or if the nerve simply remains irritable. Those who have had neurectomy may develop a stump neuroma that may be even more painful than the original problem.

Surgical intervention may be indicated should the persisting symptoms be intolerable and fail to respond to conservative measures. [51] In operating on a recurrent neuroma, the plantar approach provides more direct access to the nerve while avoiding the scarred tissue planes of the initial dorsal approach.

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Long-Term Monitoring

Follow-up depends on the individual surgeon's preference. The preferred number of visits and their timing vary from one surgeon to another; however, in general, sutures are usually removed after 2-3 weeks, and suture removal is followed by one or two more visits at 3 and 6 months.

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