scapulae

The scapulae, or shoulder blades, are two large, flat bones located on the posterior thorax. Each scapula sits over the upper ribs and is stabilized by muscles and ligaments, enabling a wide range of shoulder movements. They lie over ribs 2 through 7 and are connected to the axial skeleton mainly by the clavicle and surrounding musculature.

Anatomical features include the spine of the scapula, a prominent ridge on the posterior surface that ends laterally in the acromion. The coracoid process projects anteriorly, and the glenoid cavity articulates with the head of the humerus. The lateral and medial borders and the superior border define the margins, while the supraspinous, infraspinous, and subscapular fossae occupy the posterior and anterior aspects of the bone.

Movements involve the glenohumeral joint with the arm, the acromioclavicular joint with the clavicle, and the scapulothoracic articulation, a functional coupling with the thoracic wall. The scapula acts as a stable platform for the rotator cuff and other shoulder muscles, permitting elevation, depression, protraction, retraction, and rotation of the shoulder girdle.

Muscle attachments include serratus anterior, trapezius, rhomboids, levator scapulae, and pectoralis minor, among others. The rotator cuff muscles attach to the scapular rim and girdle the shoulder, while the inferior angle serves as an attachment point for various muscles during arm movement.

Clinical notes: fractures of the scapula are uncommon but can result from high-energy trauma. Scapular winging, usually from long thoracic nerve injury, causes medial displacement of the scapula. Dyskinesis, pain, and limited motion can accompany shoulder injuries or overuse.