ANATOMIC STUDY OF NERVE RAMIFICATIONS IN THE FOOT: SURGICAL TREATMENT OF MORTON’S PSEUDONEUROMA

Abstract

Purpose of the study: The communicating branch of the lateral plantar nerve is an anastomotic branch between the medial and lateral plantar nerves. Morton’s pseudoneuroma is usually described as resulting from the combination of one of the divisions of the medial plantar nerve and the communicating branch of the lateral plantar nerve. Surgical treatment of Morton’s pseudoneuroma can fail, leading to recurrent neuroma, or digital hypoesthesia. We performed an anatomic dissection study to search for the anatomic basis for an improved surgical technique.

Material and methods: The study included 35 feet of embalmed cadavers. A standard protocol was used for dissection. We studied the communicating branch, its frequency and size, and measured its attachment on the 3rd and 4th plantar common digital nerves. All other nerve ramifications were noted.

Results: None of the 35 dissected feet presented a macroscopic Morton pseudoneuroma. The communicating branch was present in 77% of the specimens with frequent anatomic variations concerning the size, ramifications, orientation and distance from the intermetatarsal ligament. A fine plantar cutaneous branch was often found under the intermetatarsal ligament. The bifurcation of the 2^nd and 3^rd nerves was occasions not far from the junction of the communicating branch on the 3^rd nerve, raising the risk of injury to the 2^nd nerve during surgical excision of a Morton pseudoneuroma.

Discussion: The communicating branch appears to play a role in recurrence after excision of the Morton pseudoneuroma by preventing the retraction of the 3^rd digital nerve in the muscle zone if it is not sectioned. However, wide resection of the proximal part of the 3^rd nerve and the communicating branch could lead to digital hypoesthesis if the 2^nd digital nerve is injured. The proximity of the bifurcations of the 2^nd and 3^rd nerves and of the 3^rd nerve with the communicating branch could explain this type of complication.

Conclusion: We advocate resection of the pseudoneuroma under visual control in order to carefully resect the communicating branch without injuring the adjacent nerve branches.