As a result of chronic stress associated with an intense high school weight-lifting program, a 15-year-old boy suffers an avulsion fracture of the greater tubercle of the humerus. In the ER, he displays difficulty initiating abduction of the upper limb. Which muscles was involved in this fracture?

The muscle involved in this fracture is supraspinatus.

Explanation:

Supraspinatus is one of the rotator cuff muscles, along with infraspinatus, teres minor and subscapularis muscles. Supraspinatus is located deep to the trapezius muscle in the posterior scapular region, extending from the supraspinous fossa of scapula to the proximal humerus.

Together with the other rotator cuff muscles (infraspinatus and teres minor ), supraspinatus stabilizes the glenohumeral (shoulder) joint during the movements of the upper limb. Additionally, it assists in the abduction of the arm.

Avulsion of this structure could result in detachment of any of these rotator cuff muscles, depending upon the size and scope of the fracture. However, the wrestler is unable to initiate abduction of the upper limb, which implies damage to the supraspinatus muscle.