The anatomy of the scapulothoracic articulation can be unfamiliar and complex. It is critical to understand the anatomy of this area when treating pathology of the scapulothoracic articulation (1, 2, 3, 4, 5). This is particularly true when considering arthroscopy as a treatment modality as errors in portal placement and the use of arthroscopic instruments may injure the multiple local neurovascular structures.

Muscles surrounding the scapula consist of the subscapularis anteriorly; the levator scapulae, rhomboid muscles, and serratus anterior medially; and the supraspinatus and infraspinatus muscles posteriorly (1, 2, 3, 4, 5, 6). The scapula relies on the periscapular musculature for stability; in fact, its only attachment to the axial skeleton is through the clavicle via the acromioclavicular joint and coracoclavicular ligaments (1, 3, 4). The scapula articulates with the posterior chest wall between the second and seventh ribs that are covered by the serratus anterior. There are several key neurovascular structures surrounding the scapula, which may be at risk with improper arthroscopic portal placement. These structures include the spinal accessory nerve that runs along the medial border of the scapula, branches of the superficial branch of the transverse cervical artery that runs with the spinal accessory nerve, the dorsal scapular artery and nerve that also are located near the medial border of the scapula, the suprascapular nerve and artery traversing the suprascapular notch superiorly, and the long thoracic nerve that courses distally on the anterior surface of the serratus anterior (3, 4, 5) (Fig. 15-1).

There are several potential spaces or bursae (two major or anatomic and four minor or adventitial) that are key sites of pathology that have been described in the literature (1, 2, 3, 4). The major bursae consist of the supraserratus or scapulothoracic bursa, which is located between the chest wall and the serratus anterior muscle, and the infraserratus or subscapularis bursa, which is located between the subscapularis and serratus anterior muscles (1, 2, 3, 4, 5, 6, 7, 8, 9) (Fig. 15-2). These bursae have been consistently visualized in both clinical and anatomic studies (1, 2, 3, 4, 6, 7, 8, 10, 11, 12, 13). It has been postulated that the four minor (or adventitial) bursae arise in response to inflammation, which is why these spaces are not reliably found in cadaver studies or at the time of arthroscopy. The most commonly symptomatic of these bursae is located at the superomedial angle of the scapula and can be either deep or superficial to the serratus anterior (1, 2, 3, 4). The other bursae are located at the inferior angle of the scapula (infraserratus) and the medial base of the spine of the scapula beneath the trapezius muscle (scapulotrapezial or trapezoid bursa) (1, 2, 3, 4, 5, 6, 9).

Scapulothoracic problems have been described as two disorders that are frequently related. Scapulothoracic crepitus or the so called “snapping scapula” can present as a painful or nonpainful loud grating or thumping sound with motion of the shoulder. Crepitus has been attributed to a number of causes including muscle
abnormalities (atrophy, fibrosis, or anatomic variation), bone abnormalities (rib or scapula osteochondroma; misaligned rib and/or scapula fractures; hooked superomedial angle of the scapula, i.e., Luschka tubercle; or reactive bone spurs from avulsed muscles), or other soft-tissue abnormalities (bursitis, tuberculosis, scoliosis, or thoracic kyphosis) (1, 2, 3, 4). Scapulothoracic bursitis, on the other hand, is a result of an inflamed bursa and can occur with or without crepitation. Bursitis often results from overuse with repetitive motion of the scapula over the thorax resulting in soft-tissue irritation, muscular microtears and a cycle of inflammation, and scarring (1, 3). These two clinical entities are frequently interrelated and the treating surgeon must be able to distinguish between those that are symptomatic causing dysfunction and those that are just alarming due to the noise elicited from movement but really do not cause pain.