Abstract:

Objective：To investigate the normal sonographic anatomic characteristics of the pectoralis major and the clinical value of ultrasound in diagnosing the extent and location of the pectoralis major tears. Methods:High frequency transducer was used in scanning the pectoralis major. The ultrasonographic images of 40 normal pectoralis major were obtained from 20 healthy volunteers with both sides. Longitudinal and transversal views were performed and stored. The distal tendon was identified in the transverse plane coursing superficially to the long head of the biceps brachii tendon inferior to the level of the subscapularis tendon. Eighteen cases of pectoralis major tears were analyzed retrospectively，with MRI, surgical and ultrasound follow-up results correlation respectively. Results:High-frequency ultrasound could clearly show the anatomic orientation of the normal pectoralis major. The fibers converge was like a fan into three laminae that twisted upon each other at 90° before coalescing into a single tendon of insertion. In the study, 18 patients of pectoralis major muscle tears ［average age：(37.2±15.6) years］ sustained injuries during weightlifting, basketball and impact. Three of the eighteen patients had MRI results； nine had surgical correlation； six were followed by ultrasound. Eleven were injured on the left side, and 7 on the right side. Seven were involved in the distal tendon (1 in sternal head, 2 in clavicular head, 4 in both sternal and clavicular head), five were involved the musculotendinous junction, 6 were involved muscle belly. Twelve cases were partial-thickness petoralis major tears（4 in the distal tendon， four in the muscle tendon junction，4 in the muscle belly），with the partial fiber intact, echogenicity decreased and the internal structure disordered; 6 cases (3 in the distal tendon, 1 in the muscle tendon junction, 2 in pectoralis major muscle belly) were completely disrupted, with fiber fracture and retraction, accompanied with or without hematoma formation. Conclusion:Highfrequency ultrasound can clearly show the anatomic structure of the pectoralis major. Ultrasonography can diagnose the pectoralis major tears with the extent and location of injuries，and can be used to help the clinical treatment.

Key words: Pectoralis muscles, Tendons, Lacerations, Ultrasonography