Review Question - QID 218938

This patient has a pectoralis major tendon tear, which more often involves the lower sternal head rather than the clavicular head.

Pectoralis major tears are uncommon injuries that can occur during eccentric contraction of the muscle while the arm is in extension and internal rotation (i.e. bench press). The pectoralis major is a convergent muscle with various origins along the clavicle and sternum that converge to an insertional point just lateral to the bicipital groove (Illustration A). The various muscle bellies converge near the muscle’s insertion forming anterior (clavicular) and posterior (sternal) tendon layers (Illustration B). The posterior tendon layer is predominantly made of the lower sternal segment muscle fibers, which are targeted with chest strengthening exercises for pectoralis major contouring aesthetics. The posterior sternal layer is more often torn than the anterior clavicular layer at the myotendinous insertion given its mechanical disadvantage.

ElMaraghy and colleagues performed a systematic review of pectoralis major tears to propose a novel comprehensive classification system. They reviewed 365 patients across 67 publications and proposed a new classification based on injury timing, location, and tear thickness. The authors concluded that their classification system better informs surgeons on appropriate surgical repair techniques and standardizes injury classification to better compare outcomes.

Kowalczuk and colleagues performed a retrospective case series evaluating surgically treated pectoralis major tears at their civilian institution by a single surgeon over a 14-year period (n=104 cases). The authors found that all patients were male, chronic tears (>6 weeks) were more common than acute tears, and nearly all tears occurred at the musculotendinous junction (96%). Further, partial thickness tears involving the posterior tendon layer (i.e. sternal head) were the most common tear pattern (60%). The authors concluded that most cases (100/104 reported), including chronic cases, could be primarily repaired without allograft reconstruction.

Figure A shows the asymmetry of the patient's pectoralis musculature with anterior axillary defect on their left side. Figure B shows axial MRI imaging of a full-thickness, completely torn pectoralis major tendon with retraction. Illustration A shows an image from the ElMaraghy 2012 article depicting the different portions of the pectoralis major tendon. S1-S7 represents the various sternal segments and CH denotes the singular clavicular head. Illustration B, from the same article, shows the distinction between the anterior tendon (comprising insertion of the clavicular head) and the posterior tendon (comprising insertion of the lower sternal heads).

Incorrect Answers:
Answer 2: Pectoralis major ruptures as seen almost exclusively in males.
Answer 3: Most pectoralis major ruptures can be treated with primary repair, even in chronic cases.
Answer 4: The pectoralis major is predominantly responsible for adduction and internal rotation. The anterior deltoid and coracobrachialis serve as the predominant musculature providing shoulder forward flexion.
Answer 5: Most pectoralis major ruptures occur at the myotendinous junction or insertion along the humerus. Intramuscular rupture is very uncommon, however, can occur as the result of direct trauma (i.e. stab injuries).