Surgery for Morton Neuroma Treatment & Management
- Author: Lyle Jackson, MD; Chief Editor: Jason H Calhoun, MD, FACS more...
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.
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.
Corticosteroid or local anesthetic injections may be helpful, especially when coupled with the aforementioned shoe modifications. A dorsal injection is used with 40 mg of methylprednisolone or 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. Injections should not be used indiscriminately, because the injection itself is associated with mild risk. High-quality evidence-based medicine supports corticosteroid injections for short-term (3 month) symptom relief.[23, 24] Symptom relief may be longer lasting in smaller neuromas (< 5 mm).
Alcohol sclerosing injections should be used with caution since results are not reliably effective.[25, 26, 27]
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.
Current surgical care for Morton neuroma involves a few different options for either decompressing or resecting the nerve.[29, 30] 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 weight bearing. The plantar approach is more direct, requiring less dissection, and preserves the transverse metatarsal ligament, theoretically reducing metatarsal instability.
A recent randomized controlled trial comparing dorsal to plantar approaches showed similar clinical outcomes and rates of complications between the 2 surgical approaches, but with different types of complications occurring in each group. The plantar group most commonly had minor hypertrophic scar–related complications, while the dorsal group's complications were varied. A single retrospective review from the same author also found the 2 approaches comparable.
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 weight-bearing area. This approach provides direct exposure of the nerve, since it lies plantar to the intermetatarsal ligament. Alternatively, a longitudinal incision can be made in the interspace. Weight bearing is not recommended until the sutures are removed (2-3 wk). See images below.
The dorsal approach is through a similar-sized (3-cm) longitudinal incision centered on the metatarsal head interspace.[34, 20] 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. Immediate weight bearing postoperatively is allowed with this approach. See the images below.
Regardless of the approach, it is prudent to inspect the area carefully to look for concurrent pathology such as lipomas, osteophytes, or inflamed bursae. Care must also be taken to preserve the digital vascular structures. A recent randomized controlled trial comparing dorsal with plantar approaches showed similar clinical outcomes and rates of complications between the 2 surgical approaches, but with different types of complications occurring in each group. The plantar group was more likely to have minor hypertrophic scarring.
After deciding which approach to use, the definitive surgical procedure must be performed—another somewhat controversial issue. One surgical option is simply to divide the intermetatarsal ligament and thereby create a decompression of the intermetatarsal space. This may be coupled with a neurolysis, depending on the surgeon's preference. Proponents of this ideology generally believe that decreasing the stresses on the nerve is the key aspect of successful treatment and that, by preserving the nerve, some normal nerve function can return. Furthermore, by not resecting any nerve tissue, no chance of forming a recurrent (stump) neuroma exists. A deep transverse metatarsal ligament release combined with a metatarsal shortening osteotomy has been shown to improve outcomes compared to release alone.
A second option is to perform a neurectomy, as shown below. Proponents of neurectomy believe that the key to successful treatment is elimination of the pathologic nerve tissue, while decompression would only serve to 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, since this allows proper resection of the plantar branches that may otherwise prevent the nerve stump retraction away from the weight bearing surface.[20, 36]
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.
Postoperative care depends on the surgical approach. For the dorsal approach, the patient is weight bearing 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, weight bearing is restricted to the heel only until the incision heals to prevent plantar wound complications.
Follow-up depends on surgeon preference. Number of visits and timing vary by surgeon; however, in general, sutures are usually removed after 2-3 weeks, followed with 1 or 2 more visits at 3 and 6 months.
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 may be more likely to perform surgical decompression of the nerve (and not resect it) to avoid this complication.
In the rare cases in which 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 this increased numbness caused some awkwardness with nail care but no significant disability.
Intractable plantar keratosis underneath adjacent metatarsal heads has been identified as a potential complication, likely as a result of altered weight-bearing mechanics due to releasing the intermetatarsal ligament. Wound complications are typically minor when they occur. Antibiotic treatment and/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. When 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.
Outcome and Prognosis
In general, review of the orthopedic literature from the last 20 years supports an estimate of 75-95% satisfactory results after surgical intervention regardless of technique or approach. Nonsurgical management probably results in a 20-30% success rate.
Long-term post surgical outcomes have been quantified.[20, 33, 37, 40, 41]
Coughlin and Pinsonneault monitored 66 patients (71 feet, 74 neuromas) over an average of 5.8 years. A dorsal approach was used, and a neurectomy was performed 3 cm proximal to the intermetatarsal ligament. The results were as follows:
Histology was available on 72 of the 74 specimens, and all were neuromas
Rates were excellent in 61% (no problems, none or mild pain), good in 24% (few problems, mild pain at most, would still have surgery again), fair in 8% (moderate pain, some difficulty walking, reservations about surgery outcome), and poor in 8% (continued pain and difficulty walking, regret having surgery)
Thirty percent had no shoe-wear restrictions, 53% had mild restrictions, and 17% had with major restrictions
Sixty-five percent of the feet were pain free and 4% were severely painful
Complications were 1 deep infection requiring incision and drainage; 6 superficial infections resolved with antibiotics; intractable plantar keratosis in lesser metatarsal heads 15% of the feet, one of which had metatarsophalangeal joint instability; and continued major shoe-wear restriction believed to be related to neuroma surgery in 8%
A recent study by Nery et al retrospectively followed 168 consecutive patients at a median of 7.1 years in whom nonoperative management had failed. All patients had an MRI to rule out other pathology and, after neurectomy, had a pathology-proven neuroma. Different from Coughlin, the surgery used a transverse plantar approach and preservation of the deep transverse incision. The results were as follows:
A good (no pain or paresthesia) result occurred in 89%, fair (mild pain or paresthesia without recurrence) in 7%, and poor (complications or persistent symptoms) in 4%
In all patients with a poor result, a recurrent neuroma was found on a second surgery, resected, and all are now asymptomatic
The study authors conclude that the transverse plantar incision approach for Morton neuroma resection is comparable in outcomes to other approaches. They also state that MRI is not needed for diagnosis, but was required by insurance
Akermark et al followed 55 patients with a longitudinal plantar incision for at least 2 years and found an 86% rate of overall satisfaction. Their complication rate was low (5%) and may relate to meticulous care to keep scar formation between the metatarsal heads.
Colgrove et al compared transposition versus resection in a randomized trial. At the 36- to 48-month follow-up, they found the resection group to have 86% excellent and 14% fair results; meanwhile, the transposition group had 96% excellent and 4% good results. They concluded that resection is unnecessary for symptom relief. However, to date, another repeat study has not been conducted to confirm their results.
Kasparek et al reported good-to-excellent results in 75 (77%) feet at mean 15.3 years after surgery in their retrospective series.
Future and Controversies
This article outlines some current controversies regarding Morton neuroma; the fact that the eponym is likely a misnomer is a reflection of current controversies. The histology, use of adjunctive imaging modalities, and choice of surgical procedure all involve some degree of controversy. Current and future work is addressing these issues.
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