Scapula

The scapula (shoulder blade) is a flat, triangular bone on the posterior thorax. It connects the upper limb to the trunk and provides attachment for many muscles that control shoulder and arm movement.

Key Features

Spine - posterior ridge dividing supraspinous and infraspinous fossae

Acromion - lateral end of spine, articulates with clavicle

Coracoid process - anterior hook-like projection

Glenoid cavity (fossa) - lateral, articulates with humerus

Supraspinous fossa - above spine

Infraspinous fossa - below spine

Subscapular fossa - anterior (costal) surface

Superior, medial, and lateral borders

Superior, inferior, and lateral angles

Suprascapular notch - on superior border

Articulations

•Glenohumeral joint (glenoid with humeral head) - ball and socket
•Acromioclavicular joint (acromion with clavicle) - plane synovial

Muscle Attachments

Supraspinous fossa: supraspinatusInfraspinous fossa: infraspinatusSubscapular fossa: subscapularisCoracoid process: biceps short head, coracobrachialis, pectoralis minorAcromion: deltoid (origin)Spine: trapezius, deltoidMedial border: rhomboids, serratus anteriorLateral border: teres major, teres minor

Clinical Relevance

Scapular winging occurs with serratus anterior weakness (long thoracic nerve injury) or trapezius weakness (accessory nerve injury). Scapular fractures require significant trauma. Impingement syndrome involves the subacromial space.

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Scapula FAQs

Common questions about this bone

Scapular winging is when the medial border of the scapula protrudes posteriorly. It typically results from serratus anterior weakness (long thoracic nerve injury) or trapezius weakness (accessory nerve injury).

Three muscles attach to the coracoid process: the short head of biceps brachii, coracobrachialis, and pectoralis minor. The coracoid also serves as an origin for ligaments to the clavicle and humerus.

The glenoid cavity (or fossa) is the shallow socket on the lateral scapula that articulates with the humeral head to form the glenohumeral (shoulder) joint. Its shallow depth allows wide range of motion but sacrifices stability.

The suprascapular nerve passes through the suprascapular notch (under the superior transverse scapular ligament), while the suprascapular artery passes above the ligament. The nerve supplies supraspinatus and infraspinatus.