Outcomes and intraoperative findings of revision surgery for failed subcutaneous transposition of the ulnar nerve.

Background: Ulnar neuropathy, or primary cubital tunnel syndrome, is the second most common nerve compression disorder affecting the upper extremity. Surgical management often fails due to inadequate nerve decompression at key anatomical sites. This study evaluates the failure of subcutaneous ulnar nerve transposition and identifies the anatomical factors contributing to symptom persistence or recurrence. Methods: We reviewed the medical records of 21 patients who underwent revision surgery for failed subcutaneous ulnar nerve transposition performed between 2001 and 2019. Clinical assessments included Tinel's sign, paresthesia, muscle atrophy, and McGowan's score. The revisions involved submuscular or subcutaneous transpositions with comprehensive decompression at multiple sites, including the arcade of Struthers, the medial intermuscular septum, and the deep flexor-pronator aponeurosis. Clinical outcomes were evaluated at a minimum follow-up of two years using Messina's criteria, the British Medical Research Council sensory grading scale, and the McGowan's score. Results: Intraoperative findings revealed proximal compression at the arcade of Struthers in 71.4% of the patients, distal compression at the deep flexor-pronator aponeurosis in 38%, and an intact medial intermuscular septum in 76.2%. Postoperatively, 14 patients (66.6%) achieved excellent results according to Messina's criteria and 14 attained S4 on the British Medical Research Council sensory grading scale. With regard to McGowan's score, 14 patients reached grade 0, 5 reached grade 1, 1 reached grade 2, and 1 reached grade 3. Overall, 90.5% of the patients were satisfied, with significant pain reduction and sensory loss improvement. Conclusion: Inadequate decompression at key anatomical sites, like the arcade of Struthers, the medial intermuscular septum, and the deep flexor-pronator aponeurosis, significantly contributes to the failure of subcutaneous nerve transposition. Triceps snapping may also be a cause of symptom persistence. Surgical approaches that address all potential compression sites can improve outcomes. Research should focus on refining surgical techniques that ensure complete decompression during ulnar nerve transposition.