Anterior Subcutaneous Versus Submuscular Transposition of the Ulnar Nerve for Idiopathic Cubital Tunnel Syndrome: A Matched Retrospective Comparative Study

Royalty: Elsevier, Biomet, Skeletal Dynamics (Osterman) Consulting Fee: Arthrex, New Clip, Acumed (Osterman) Contracted Research: Acumed (Osterman) Ownership Interest: Mission Surgical Innovations (Kane) We tested the null hypothesis that submuscular and subcutaneous ulnar nerve transposition would have similar outcomes in matched cohorts of patients with idiopathic cubital tunnel syndrome (CuTS). We conducted a retrospective study of patients who underwent primary anterior transposition of the ulnar nerve for idiopathic CuTS over a 7-year study interval. Operative reports were reviewed to determine which patients had submuscular versus subcutaneous transposition, and patients from each group were matched 1:1 based on age and sex. Baseline demographics and medical histories were obtained from chart review. Modified McGowan Grades were assigned to each patient preoperatively and postoperatively. Numerical outcomes were compared using paired t-testing for preoperative versus postoperative values whereas comparisons between cohorts utilized independent t-testing. A total of 232 patients (116 subcutaneous, 116 submuscular) were included. There were no significant differences between the groups based on baseline demographics (Table 14-1). Across all patients, grip strength improved from 67.6% ± 28.7% of the contralateral side preoperatively to 80.1% ± 28.5% postoperatively; paired t test; P < .001). Key pinch strength improved marginally from 68.0% ± 27.3% of to 73.4% ± 31.8%, although this was not significant; P = .175). Improvements in grip and key pinch strength were not significantly different between the subcutaneous and submuscular cohorts. There was no significant difference between the groups for a change in modified McGowan grade (Table 14-2). Twenty patients (11 subcutaneous, 9 submuscular; P = .64) underwent revision surgery at a median interval of 14 months (range, 3.6–107 months). Nine subcutaneous transpositions were revised to submuscular transpositions for recurrent symptoms owing to perineural scarring and 2 were treated with revision neurolysis. Four submuscular transpositions failed owing to new-onset nerve subluxation and were revised to subcutaneous transpositions, while the remaining 5 were treated with revision neurolysis, including placement of an adhesion barrier in 3. Older age was the lone risk factor predicting revision surgery (49.1 ± 13.5 years in non-revised patients vs 56.8 ± 14.0 revised; P = .029). •Subcutaneous and submuscular ulnar nerve transposition have equivalent outcomes when performed in similar cohorts of idiopathic CuTS patients.•Improvements in grip strength were statistically significant across the full study cohort but were not different between the 2 transposition groups.•Subcutaneous transpositions were more likely to fail owing to perineural scarring whereas submuscular transpositions failed owing to subluxation.•Older age was the only risk factor for requiring revision surgery.Table 14-1Baseline characteristics of matched transposition cohortsVariableSubcutaneous (116)Submuscular (116)P valueAge, mean ± SD, years48.8 ± 12.850.9 ± 14.5.245Body mass index, mean ± SD28.6 ± 5.728.6 ± 6.0.989Symptom onset to surgery, mean ± SD, months19.4 ± 37.819.6 ± 21.7.965Male: Female58:5858:581.0Dominant extremity, n (%)58 (50%)53 (45.7%).551Diabetes, n (%)17 (14.7%)11 (9.5%).227Active smoker, n (%)21 (18.1%)29 (25%).201Subluxating nerve, n (%)60 (51.7%)49 (42.2%).148Modified McGowan grade Grade I3141 Grade IIA4835.203 Grade IIB2834 Grade III96Nerve conduction velocity, mean ± SD, meters/s44.0 ± 14.447.3 ± 13.2.172Follow-up duration, mean ± SD, months15.6 ± 11.417.9 ± 15.8.205 Open table in a new tab Table 14-2Change in Modified McGowan GradePostoperative Modified McGowan Scores012A2B3TotalPreoperative Modified McGowan Scores126*39†4ˆ3ˆ0722A17*43*21†2ˆ0832B10*24*21*7†06233*2*2*6*2†15Total5610848182232Note: * - designates improvement of at least one gradeˆ - designates worsening by at least one grade† - designates unchanged Open table in a new tab Note: * - designates improvement of at least one grade ˆ - designates worsening by at least one grade † - designates unchanged