Open Intermetatarsal Ligament Release Advocated as First Surgical Treatment of Morton's Neuroma

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The cause of Morton's neuroma remains controversial, but the most likely explanation is chronic inflammation and irritation of the interdigital nerve as it courses between the metatarsal heads and exits from below the intermetatarsal ligament (IML). Conservative therapy often fails, and the traditional surgical treatment is to transect the common digital nerve and excise the neuroma.

Inherently, though, neuroma excision creates permanent forefoot numbness at and distal to the operative site. Its other outcomes are notoriously unpredictable. Even when the procedure is performed perfectly, with uneventful healing, a stump neuroma may develop, which can result in substantial morbidity and worsening symptoms. In addition, there is a 15%–40% risk that the patient will need an equally if not more unreliable operative revision.

For the past six years, orthopedic surgeons at Massachusetts General Hospital have been treating recalcitrant Morton's neuroma with simple nerve decompression, similar to what is done for nerve compression syndromes elsewhere in the body, such as carpal tunnel syndrome. In Foot & Ankle Specialist, Mohamed Abdelaziz Elghazy, MD, PhD, former postdoctoral research fellow, Gregory Waryasz, MD, foot and ankle surgeon and sports medicine physician, Daniel Guss, MD, MBA, orthopaedic foot and ankle surgeon, and Christopher W. DiGiovanni, MD, chief of the Foot and Ankle Center, and colleagues present a case series.

Study Details

The researchers retrospectively studied 12 adults between August 2014 and July 2018 with clinically diagnosed Morton's neuroma who did not respond to at least three months of conservative therapies and underwent open IML release without excision of the neuroma. The average follow-up time was 13.5 months (range, 6–32).

The article reports the surgical technique in detail. Most notable is the importance of ensuring intraoperatively that the nerve is able to float upward, especially at the distal extent of the incision where scissor dissection may be required.

Outcomes

• The average pain rating on a 0–10 visual analog scale improved from 6.4 preoperatively to 2 at final follow-up (P=0.002)
• One patient had recurrent pain six months after surgery, which was relieved with shoe modification; no others had shoe restriction postoperatively
• No patient required revision surgery
• No postoperative infections or other complications were reported

Recommendations

Based on these results, which seem at least equal to those of neuroma excision, IML release should be the new first-line treatment for Morton's neuroma that does not respond to conservative measures. If symptoms persist afterward, there is still an option for neuroma excision without having "burnt a bridge."

Although some patients stated they were "100% better" after IML release, others did not experience complete relief from interspace neuroma pain. This is worth emphasizing to patients during decision-making about surgery as a way to set expectations. An important point is that no patient was made worse.

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