Objective: MR imaging is the optimal imaging technique to study the normal and abnormal conditions of the pectoralis major muscle and tendon unit. The purpose of this study was to use MR imaging to provide an anatomic survey of the normal pectoralis major tendon and its insertion and to compare these findings with surgically proven cases of rupture.
Conclusion: MR imaging shows the normal pectoralis major myotendinous unit has low signal intensity on both T1- and T2-weighted images. Reliable anatomic landmarks for visualization and examination of injuries to the muscle and myotendinous unit include the quadrilateral space, or the origin of the lateral head of the triceps, as the superior boundary and the deltoid tuberosity as the inferior boundary of the intact tendon of insertion. Failure to visualize a normal insertion within these boundaries should prompt a dedicated search by the radiologist for rupture and retraction of the tendon medially.