Comprehensive Study Notes on the Scapula

General Classification and Articulations

The scapula is classified as a flat bone type. In its anatomical position, it serves as a central component of the pectoral girdle. It is designed to articulate with two primary structures: the humerus (forming the glenohumeral joint) and the clavicle (forming the acromioclavicular joint). Its position is generally described as antero-lateral on the thoracic cage.

Side Determination and Borders

Determining the side of the scapula depends on identifying specific borders and the orientation of the glenoid cavity. The lateral border is notably thick and extends downwards from the glenoid cavity. In contrast, the medial border is thin. The superior border is characterized as the shortest of the three borders. For correct anatomical orientation, the glenoid cavity must be positioned antero-laterally.

Surface Anatomy

The scapula possesses two distinct surfaces. The dorsal surface, or the posterior aspect, is convex in shape. This surface is divided by the spine of the scapula. The costal surface, also known as the anterior aspect, is concave. This concavity is referred to as the subscapular fossa and serves as the primary origin site for the subscapularis muscle.

Primary Processes of the Scapula

There are three main processes on the scapula that provide attachment points and structural integrity. The acromion process is the most superior portion, located superior to the deltoid muscle. The coracoid process is situated anterior to the acromion process. It can be felt approximately $2.5\,cm$ below the clavicle. The spine of the scapula is a triangular bony plate that is a continuation of the acromion process. It runs across the dorsal surface, effectively dividing it into two distinct regions: the supraspinous fossa and the infraspinous fossa.

Fossae, Tubercles, and Joints

The scapula features several landmarks related to muscle attachments and joint formation. The supraglenoid tubercle is a bulged part located above the glenoid cavity and serves as a point of origin. The infraglenoid tubercle is a bulged part located below the glenoid cavity. The supraspinous fossa is the area above the spine and is the origin site for the supraspinatus muscle, while the infraspinous fossa is located below the spine and is the origin site for the infraspinatus muscle. The glenoid fossa is the shallow articular surface that facilitates the glenohumeral joint.

Clinical Anatomy and Development

In terms of development, the scapula originates in the neck region during the embryonic stage and eventually migrates downward to its final thoracic position. A clinical condition associated with this developmental process is known as Spengel's deformity. This occurs when the scapula fails to descend properly from its initial position in the neck to its normal anatomical location on the upper back.