Injection Technique for Pectoralis Major Tear Syndrome

Indications and Clinical Considerations

The pectoralis major muscle is susceptible to trauma ranging from microscopic tears of the muscle substance caused by heavy exertion to macroscopic partial tearing of the muscle or, in extreme cases, full-thickness tearing with associated hematoma formation and cosmetic deformity ( Fig. 38.1 ). In addition, the pectoralis major tendon can rupture at its point of insertion into the crest of the greater tubercle of the humerus ( Fig. 38.2 ).

The clinical presentation of pectoralis major tear syndrome varies because of the number of causes, with the severity of symptomatology directly proportional to the amount of trauma sustained by the muscle and/or its tendons. The presenting symptom of pectoralis major tear syndrome is the acute onset of anterior chest wall pain after trauma to the muscle sustained while performing activities such as bench pressing or repelling down cliffs. The severity of pain will be proportional to the amount of trauma sustained. The patient with pectoralis muscle tear syndrome may also report varying degrees of weakness with internal rotation of the humerus. If a complete tear of the muscle or rupture of the tendon occurs, there will be acute bulging of the anterior chest wall with contraction of the muscle in a manner analogous to the Popeye bulge or Ludington sign associated with rupture of the biceps tendon. In addition to medial displacement of the muscle belly of the pectoralis major, a dropped nipple sign will often be present ( Fig. 38.3 ). If the complete rupture is not promptly repaired, further muscle retraction and calcification will occur, worsening the functional disability and cosmetic deformity.

The patient with pectoralis major tear syndrome will report the acute onset of pain in the anterior chest after trauma to the pectoralis major muscle and/or tendon. If the trauma is significant, hematoma formation will be clearly visible; with rupture of the tendon at its insertion site into the humerus, impressive ecchymosis of the arm and anterior chest wall may seem out of proportion to the amount of trauma perceived by the patient. Active internal rotation of the humerus against examiner resistance may reveal weakness. If there is significant disruption of the muscle or rupture of the tendon, the patient will be unable to reach behind his or her back. As mentioned previously, if complete tear of the muscle or rupture of the tendon has occurred, there will be bulging of the anterior chest wall with contraction of the pectoralis major against the unopposed torn distal muscle and/or tendon. Loss of the axillary fold may also be present. Although not completely diagnostic of pectoralis major tear syndrome, this physical finding should prompt the examiner to obtain a magnetic resonance imaging (MRI) or ultrasound scan of the affected proximal humerus and shoulder and anterior chest wall to further clarify and strengthen the diagnosis.

MRI and ultrasound imaging of the shoulder, proximal humerus, and anterior chest wall provides the clinician with the best information regarding any pathology of these anatomic regions. MRI scan is highly accurate and helps identify abnormalities that may require urgent surgical repair, such as large complete muscle tears and/or tendon rupture ( Fig. 38.4 ). MRI and ultrasound imaging of the affected anatomy will also help the clinician rule out unsuspected pathology that may harm the patient, such as primary and metastatic tumors. In patients who cannot undergo MRI scanning, such as a patient with a pacemaker, computed tomography is a reasonable second choice. Radionuclide bone scanning and plain radiography are indicated if fracture or bony abnormality, such as metastatic disease of the proximal humerus, shoulder, or anterior chest wall, is being considered in the differential diagnosis.

Screening laboratory testing consisting of complete blood cell count, erythrocyte sedimentation rate, and automated blood chemistry testing should be performed if the diagnosis of pectoralis major tear syndrome is in question.

Clinically Relevant Anatomy

A broad, thick, fanlike muscle, the pectoralis major arises from the anterior surface of the proximal clavicle, the anterior surface of the sternum, the cartilaginous attachments of the second through sixth and occasionally seventh ribs, and the aponeurotic band of the obliquus externus abdominis muscle (see Fig. 38.2 ). These muscle fibers overlap, with some running upward and laterally, others running horizontally, and others running downward and laterally, with all ending in a broad flat tendon that inserts into the crest of the greater tubercle of the humerus.