A Closer Look At Endoscopic Nerve Decompression For Morton’s ‘Neuroma’

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Author(s): 
Damien Dauphinée, DPM, FACFAS, CWS-P

What The Research Reveals About Endoscopic Release

Researchers have shown that an endoscopic release of the deep transverse intermetatarsal ligament is quite effective in relieving the pressure on the nerve.4 In a 1994 cadaveric study, Barrett and Pignetti, using an endoscopic approach, released the deep transverse intermetatarsal ligament, leaving the entrapment neuroma intact. In the prospective study, 17 patients with 19 neuromas had endoscopic decompression of the intermetatarsal nerve. Ten of 17 patients required no pain medications and four others needed fewer than three tablets of acetaminophen (500 mg)/hydrocodone (5 mg).4 Fifteen of 17 patients reported excellent results while one patient had a fair result and one had a poor outcome.

   Barrett and Walsh subsequently published a retrospective look at 69 patients who had decompression of 96 interspaces.5 Of the 96 interspaces released, 39 were second interspaces and 57 were third interspaces. The authors reported 86 percent excellent or good results, and 14 percent poor results. Of the interspaces with poor results, Barrett and Walsh noted five patients required further surgery and had a traditional neurectomy. The study adds that none of the patients who had interspace decompression developed a true amputation neuroma.

A Step-By-Step Guide To Surgical Technique

When it comes to endoscopic nerve decompression for Morton’s neuroma, I use a single portal approach with a second incision proximal to the interspace for the metatarsal retractor. The endoscopic surgical instrumentation set Edintrak (Instratek) contains the ideal metatarsal retractor along with a facial elevator instrument to bluntly dissect the tissue planes. The set also has an obturator and cannula for appropriate placement of the conduit (cannula) for the placement of the 2.7-mm, 30-degree endoscope. The dorsal portal incision allows for placement of a metatarsal retractor, which places tension across the deep transverse intermetatarsal ligament. This allows for easier visualization and transection.

   The surgeon makes a second incision transversely in the web space, which allows for placement of the obturator and cannula beneath the deep transverse intermetatarsal ligament. This configuration and the oval-shaped cannula eliminate the need for the third incision to allow for passage of the cannula or obturator out of the foot. After fully visualizing the deep transverse intermetatarsal ligament, one would transect the ligament using a curved hook blade.

   The surgeon can visualize separation of the transected edges of the deep transverse intermetatarsal ligament by placing further traction on the metatarsal retractor in the dorsal portal incision. One can usually identify and protect the lumbrical tendon during the procedure.

In Conclusion

In my experience, the endoscopic decompression of the intermetatarsal nerve technique is efficacious. Due to the minimal invasiveness of the technique and the preservation of the neurovascular structures, I have seen no vascular compromise to a digit in any patient in whom I have decompressed adjacent interspaces. The entire procedure takes approximately six to eight minutes and one can perform it bilaterally in under 15 minutes when symptoms exist on both sides.

   Surgeons can allow patients to bear weight immediately in a post-op shoe. Have patients bring a loose fitting athletic shoe with them to the first post-op appointment. One would dress the stab incisions with Telfa bandages and then the patient resumes normal bathing routines.

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Dr Craig Lowesays: July 24, 2012 at 1:57 pm

Microsurgical dissection with laser ablation of proximal and distal nerves works very well.

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