Review Question - QID 220091

Pectoralis major ruptures follow a predictable pattern, with the sternocostal head tearing first and often in isolation. The clavicular head is less frequently involved. The sternocostal head is innervated by the lateral and medial pectoral nerves, depicted as nerves A and E in Figure 1, respectively (answer choice 2).

Pectoralis major (PM) ruptures are acute injuries that most commonly affect males aged 20-40 during work-related activities or weight-lifting. Ruptures often occur during the eccentric contraction of a bench press, which puts the arm in a position of extension, abduction, and external rotation. The PM is a multipennate muscle, made up of the more superior clavicular head and the more inferior sternocostal head. During a PM rupture, a predictable pattern of rupture occurs with the inferior sternocostal head tearing first, followed by the clavicular head. The PM has dual innervation, with the clavicular head receiving primary innervation from the lateral pectoral nerve (C5-C7), while the sternocostal head has dual innervation from both the lateral and medial pectoral nerves (C5-T1). Clinically, patients present with pain, weakness in adduction and internal rotation, and possible ecchymosis and a visible defect along the anterior axillary fold. MRI is the gold standard for diagnosis, allowing the surgeon to identify the location and extent of the rupture. Treatment ranges from nonoperative management in low-demand individuals to surgical repair, which is favored for complete ruptures in active patients.

Kowalczuk et al. published a review of pectoralis major ruptures. These injuries often result from eccentric contractions during activities such as bench pressing in young, active males. Prompt and accurate diagnosis focuses on physical examination, with key findings including swelling, ecchymosis, loss of the anterior axillary fold, and a decreased pectoralis major index. For acute injuries, surgical intervention yields superior functional outcomes and a higher return to activity than nonoperative management. Chronic injuries are challenging, often requiring allograft or autograft utilization.

Thompson et al. provide another comprehensive review of pectoralis major ruptures. The authors note an increase in incidence in ruptures, possibly attributed to an increase in anabolic steroid use that has been closely linked to ruptures. Regarding treatment, nonoperative treatment is typically reserved for patients with significant comorbidities, older age, incomplete tears, or irreparable damage. Nonoperative treatment may allow a full range of motion but typically results in strength loss. Surgical intervention is ideally performed within six weeks of injury, as delays beyond eight weeks may require grafting.

Figure 1 is a depiction of the brachial plexus. Illustration 1 demonstrates the same image with the nerves of the brachial plexus labeled. Illustration 2, from the Kowalczuk review, is an anterior view of the delineated segments of the pectoralis major. The superior clavicular head (CH) and the multiple sternocostal heads (S1-S7) are seen with their respective origins and inserting on the proximal humerus just lateral to the bicipital groove.

Incorrect Answers:
Answer choices 1, 3, 4, and 5 are incorrect as they do not appropriately identify the lateral pectoral nerve (A) and the medial pectoral nerve (E) in Figure 1 as the dual innervation to the sternocostal head of the pectoralis major.
The nerves in Figure 1 are labeled as follows:
A: Lateral pectoral nerve (C5-C7), which innervates the pectoralis major clavicular and sternocostal heads.
B: Suprascapular nerve (C5-C6), which innervates the supraspinatus and infraspinatus.
C: Thoracodorsal nerve (C6-C8), which innervates the latissimus dorsi.
D: Medial brachial cutaneous nerve (T1), which provides sensory innervation to the medial arm.
E: Medial pectoral nerve (C8-T1), which innervates the pectoralis minor and pectoralis major sternocostal head.