Superficial Peroneal Nerve Entrapment: Diagnosis and Surgical Management. A Retrospective Study of 46 Patients

CATEGORY: Ankle INTRODUCTION/PURPOSE: Superficial peroneal nerve entrapment (SPNE) is an uncommon and often misdiagnosed condition which can lead to pain or paresthesia of a patient’s distal anterolateral leg and dorsal foot. A past medical history of an ankle sprain, specifically an inversion sprain, places SPNE on the differential diagnosis. Mismanagement of SPNE may result in continued lower leg dysfunction, unnecessary medical procedures, increased medical costs, and patient frustration. The purpose of our study was to describe an alternative diagnostic technique for SPNE and clinical outcomes following surgical decompression. METHODS: Using ICD-9/10 and CPT codes, we identified 46 patients in the private practice of a single foot and ankle orthopaedic surgeon who underwent a SPN surgical decompression between 2012 and 2017. A thorough chart review confirmed all patients underwent an SPN decompression. Additionally, the primary author compiled our variables of interest (mechanism of injury, prior medical management of ankle pain, physical exam findings, diagnostic testing, intraoperative findings, and resolution of pain or paresthesia) from this chart review. RESULTS: 46 patients (40.1 ± 14.6 years of age; 11 males and 35 females) underwent a decompression of the SPN. Average time to evaluation was 2.8 ± 5.9 years (range: 0 - 25). Ten of 46 patients (22%) reported a history of inversion ankle sprain. Positive exam findings were: tender to palpation at the fascial exit point 40/46 (87%) and positive Tinel’s sign 38/46 (84%). Pre-operative SPN diagnostic nerve block at point of maximum tenderness was performed in 44/46 patients (96%). 31/44 (70%) patients reported complete pain relief after diagnostic block. Of the 31 patients, 26 (84%) reported post-operative pain improvement. When cases were isolated to SPN entrapment with complete pre-operative pain relief following diagnostic nerve block, 18/19 (95%) experienced complete post-operative pain relief. CONCLUSION: A thorough examination of the foot and lower leg can appropriately diagnose SPNE using palpation of fascial exit point and a positive Tinel’s sign. Additionally, a nerve block proved clinically useful as an effective technique for SPNE diagnosis. Patients undergoing an isolated SPN decompression experienced pain improvement at higher rates compared to patients with concomitant surgical procedures. Future work is needed to determine if a positive diagnostic nerve block is a predictor of post- operative pain improvement. Further, while preliminary evidence is encouraging, larger cohorts across various patient populations are needed.