Factors Associated with Poorer Outcomes from Triceps Motor Branch to Anterior Axillary Nerve Transfer: A Case-Control Study.

ABSTRACT

INTRODUCTION: We sought to identify predictors of failed triceps motor branch transfer to the anterior division of the axillary nerve (AN) for shoulder abduction reconstruction after a brachial plexus injury (BPI). METHODS: A case-control study of adult AN or brachial plexus patients treated with a triceps motor branch transfer to the anterior division of the AN with a minimum 18 months of follow-up was performed. The failure group (case group) was defined as modified British Medical Research Council muscle scale (mBMRC) postoperative deltoid grade ≤2 and was compared to the successful outcome group (control group), defined as mBMRC postoperative deltoid grade ≥3. Clinical variables, injury mechanism, time from injury to surgery, root avulsion status, electrodiagnostic studies, rotator cuff injuries, scapula fracture, Disabilities of the Arm Shoulder and Hand scores, and preoperative triceps strength were analyzed. Subgroup analysis was performed for patients with isolated AN injuries and those with BPI. RESULTS: A total of 69 patients met inclusion/exclusion criteria, of whom 23 regained ≥M3 deltoid muscle strength and 52° ± 69° of shoulder abduction (successful outcome group) and 46 regained ≤M2 deltoid muscle strength and 27° ± 30° of shoulder abduction (failure group). Preoperative triceps weakness (M ≤4) was significantly more common in the failure group (63% vs. 30%, P = 0.032); preoperative triceps muscle fibrillations were significantly more common in the failure group (61% vs. 30%, P = 0.02). Isolated AN injuries presented better preoperative motion and postoperative outcomes results compared to BPI. CONCLUSIONS: Use of triceps motor branch associated with fibrillations or weakness resulted in statistically poorer outcomes compared to the use of a normal triceps motor branch in the restoration of anterior AN function after nerve transfer.