The subscapular and subcoracoid bursae: descriptive and functional anatomy.

The subscapularis and subcoracoid bursae, as well as the subscapularis muscle, were studied in 42 fresh cadaveric shoulders. Fibrous bands were found in the medial part of the muscle; they were intercalated with the distal tendon-like bands. The superior distal fibrous band was always found to be thicker than the others. Strong fibrous attachments of the subscapularis muscle were found along the lateral border of the scapula as well as along the medial third of the bony crests in the subscapular fossa. Between the crests, the muscle bundles were directly attached to the bone. In the lateral part of the scapula, the subscapularis muscle had only weak connective links with the bone. The subscapularis bursa was found in all cases as a pouch strongly attached to the scapular neck and the adjacent part of the joint capsule. The top of the bursa was linked to the coracoid process by a fibrous attachment called the suspensory ligament. The subcoracoid bursa had only weak connective links with the coracoid process. In 28% of cases, the subscapularis and subcoracoid bursae merged into a unique wide bursa. The subscapular bursa had two types of links with the muscle: (1). weak connective links with the superficial muscle bundles and (2). at least 2 fibrous arcs joining the lateral tendon-like bands, the bursa, and bony crests of the subscapularis fossa. These arcs allow the bursa to follow the course of the muscle exactly. During movements of the glenohumeral joint, the subscapularis muscle sustains huge changes of orientation, particularly the upper part of the muscle that coils around the coracoid process. The strong superior fibrous band enables the muscle to maintain contact with the coracoid process. It is the function of the subscapularis and subcoracoid bursae to manage the friction of the superficial fibers against the scapular neck, the humeral head, and the coracoid process.