Other Trauma Topics

A 52-year-old recreational surfer presents with shoulder pain and weakness after being hit forcefully by a wave while trying to recover his board with his arm in hyperabduction and external rotation. On examination, he has a positive bear hug test, active internal rotation to neutral on the affected side, and passive external rotation of 100 degrees compared to 70 degrees on the unaffected side. He comes to the clinic with an MRI, a representative image of which is shown in Figure A. You are planning to book him for a rotator cuff repair with a suprapectoral arthroscopic biceps tenodesis. Injury to which of the following structures most likely contributed to the findings shown in Figure A?