Increased postoperative deltoid signal seen after suprapectoral biceps tenodesis: potential risk to the anterior branch of the axillary nerve.

BACKGROUND: Arthroscopic suprapectoral biceps tenodesis is a common procedure for lesions of the long head of the biceps in the setting of anterior shoulder pain. However, the distal portal poses a theoretical risk to the terminal branches of the axillary nerve as the nerve travels from posterior to anterior to innervate the anterior deltoid. The purpose of this retrospective cohort study was to assess for axillary nerve branch injury, identified by deltoid signal change in postoperative magnetic resonance imaging (MRI) in patients who underwent an arthroscopic suprapectoral biceps tenodesis.

METHODS: Patients who underwent rotator cuff repair with a concomitant arthroscopic suprapectoral biceps tenodesis had a postoperative MRI, and at least 1 year of follow-up was included. The incidence of increased deltoid signal consistent with injury to an anterior branch of the axillary nerve on proton density fat-saturated sequences was collected. Age, sex, body mass index (BMI), and patient-reported outcome measures (PROMs), including the American Shoulder and Elbow Surgeons Shoulder (ASES) score, patient-reported outcomes measurement information system pain, physical function, and upper extremity scores, and single assessment numeric evaluation score were compared in patients with and without increased deltoid signal on postoperative MRI. P < .05 was used for significance.

RESULTS: Twenty-four patients were eligible for inclusion (9 female, average age 59.0 ± 10.1, BMI 27.6 ± 6.7). Edema-like signals within the anterior deltoid musculature was observed in 9 patients on postoperative MRI. Two patients had a second follow-up MRI performed, which demonstrated resolution of signal, and one patient required a second surgery for release of adhesions. Patients with increased deltoid signal had higher BMI (P = .03). There was no difference in any other demographic or postoperative patient-reported outcome measure between patients with increased signal and those without at any follow-up time point. No patient demonstrated persistent weakness or numbness in the axillary nerve distribution at final follow-up.

DISCUSSION: Over one third of patients in our cohort had MRI evidence of axillary nerve branch injury as seen on proton density fat-saturated MRI sequences postoperatively. The distal arthroscopic portal for a suprapectoral biceps tenodesis may place anterior terminal branches of the axillary nerve at risk for injury. Additional investigation and strategies for avoidance of nerve injury in this area should be pursued.