Photo by Michael Connell
The pectoralis muscle is a popular muscle for men and boys to develop. Women are drawn to "chiseled pecs", which is more than enough motivation for men to work on enlarging them.
Weightlifters are particularly prone to injuries of this muscle, and pectoralis tears are seen most often in young, athletic males. Patients with a ruptured pectoralis major present in the acute aftermath of the injury, with pain, extensive swelling, and ecchymosis of the anterior chest wall, axilla, and medial aspect of the affected arm. Injured patients frequently report a "pop" at the time of the injury.
Connell et al. (Radiology 210:785-791, 1999) described the proper technique used to image the pectoralis major. In 2000, Lee et al. (AJR 174:1371-1375) performed a beautiful cadaveric study, and described some salient features of the pectoralis major on MRI:
---> the pectoralis major tendon crosses anterior to the biceps tendon to become a thin, triangular-shaped structure at its insertion at the lateral lip of the intertubercular groove
---> one reliable landmark for the superior margin of the pectoralis insertion is the quadrilateral space, best seen in the axial plane. The superior edge of the pectoralis major insertion typically is identified at the level of, or within 1-1.5 cm inferior to the quadrilateral space (range, 0-1.2 cm).
---> another reliable landmark is the origin of the lateral head of the triceps muscle. The superior edge of the pectoralis major insertion is reliably identified on the anterior aspect of the humerus, approximately 5-10 mm superior to the level at which the lateral head of the triceps is first identified.
Here is an example of axial images through the normal pectoralis major tendon, superior to inferior, illustrating these principles:
Green arrow = normal pectoralis major tendon. Orange arrow = latissimus dorsi tendon. Note the proximal aspect of the lateral head of the triceps muscle (pink arrow) and vessels within the quadrilateral space (blue arrow).
In this case, a 25 year old male injured his chest during a take down of an opponent during mixed martial arts training. He presented for his MRI approximately 1 week after his injury.
(A) Axial intermediate image identifies an avulsion of the pectoralis major tendon at its insertion. Note the torn, retracted tendon (red arrows) and the biceps tendon (green arrow) which is displaced anteriorly. MRI clearly identifies the end the torn tendon (yellow arrow). (B) Axial T2 fatsat image better shows the edema associated with the injury.
Compare this appearance with a normal pectoralis tendon:
An oblique coronal T2 fatsat image of our patient shows marked fluid and edema (red arrows) at the myotendinous junction, the pectoralis major muscle (yellow asterisks), and the cephalic vein in the deltopectoral groove (green arrow):
The MRI scan precisely depicted the nature of the injury and allowed appropriate presurgical planning. The patient was operated on three days later, and the tear was repaired successfully.
When ordering an MRI to assess a possible pectoralis tear, it is generally best to order a “MRI of the chest”. If one requests an “MRI shoulder” the MRI technologist may inadvertently use a standard shoulder imaging protocol, which is very different than the protocol used to assess the pectoralis major. The standard shoulder protocol will not answer the clinical question.
In general, early surgical repair is associated with a better outcome for the athlete, with earlier return to full strength and range of motion. Immediate diagnosis avoids surgical delay, which has the advantage of avoiding adhesions, muscle retraction, and atrophy, which can occur as early as 6 weeks after the initial injury (Lee et al. AJR 174:1371-1375).
In the past, tears that have reached the chronic stage have been considered irreparable injuries. More recently, even chronic tears are addressed surgically, and still have a good outcome (Aarimaa et al., Am J Sports Med 32:1256-1262, 2004).
Vic David MD