Classic history and presentation: Look for acute medial upper arm pain in a young man after weightlifting. A pop, snap, or tear may be felt by the patient with associated pain and deformity at the upper chest and shoulder region with swelling, ecchymosis, and bruising in the arm and chest. Range of motion may be limited by pain.
Prevalence: Pectoralis major rupture is predominantly seen in men who are between the ages of 20 and 40 years. While pectoralis major rupture is regarded as a rare condition, there has been an increased incidence recently, attributed to increased interest in weight training and fitness.
Risk factors: Weightlifting (especially bench pressing). It may also be seen after wrestling, boxing, and rugby. It is thought to occur overwhelmingly more often in male patients as they typically engage in higher energy activities, have less elastic / compliant tendons (their tendons are mechanically stiffer), and have a lower tendon-to-muscle ratio. Studies have shown a strong association between pectoralis major rupture and anabolic steroid use because these drugs may cause tendons to become stiffer and decrease their ability to absorb energy.
Pathophysiology: The pectoralis major muscle consists of two heads. The clavicular head originates from the medial half of the clavicle, and the sternocostal head originates from the sternum, second through sixth ribs, and external oblique aponeurosis. The sternocostal head comprises at least 80% of the pectoralis major muscle and is the most common site of rupture. Both muscle heads insert on the intertubercular sulcus of the humeral shaft. Tendon rupture predictably occurs in an inferior to superior direction, starting at the sternocostal head and ascending to the clavicular head. Ruptures are most likely to occur while the inferior fibers of the sternal head are maximally stretched when the humerus is 30 degrees of extension from neutral, which is why bench pressing is a very common mechanism of injury, whereby the pectoralis major is under resisted adduction and internal rotation.
The pectoralis major sternocostal head is responsible for adduction and internal rotation of the arm, while its clavicular head contributes to forward flexion.
Grade / classification system: Tietjen classification of pectoralis major ruptures are made based on MRIs.
- Type I – muscle contusion / sprain
- Type II – partial tear
- Type III – complete tear
- Location A: muscle origin
- Location B: muscle belly
- Location C: myotendinous junction
- Location D: tendon avulsion off humerus
- Location E: bony tendon avulsion off humerus
- Location F: tendinous rupture