Lecture Notes: Scapula Anatomy

Overview

• The scapula is a large, flat, triangular bone in the posterior lateral chest wall.
• Located opposite the second to seventh ribs.
• Part of the shoulder girdle.

Surfaces

Coastal Surface

• Faces forwards and medially.
• Features the subscapular fossa.
• Contains several ridges.

Dorsal Surface

• Divided into supraspinous and infraspinous fossae by the spine.
• Lateral border of the spine: spinoglenoid notch.

Borders

Lateral Border

• From glenoid cavity to inferior angle.
• Infraglenoid tubercle below glenoid cavity.

Medial Border

• From superior to inferior angle.

Upper Border

• From superior angle to suprascapular notch.
• Suprascapular notch transmits the suprascapular nerve.

Angles

Inferior Angle

• Intersection of lateral and medial borders.
• At the level of the seventh rib.

Superior Angle

• Intersection of medial and superior borders.

Lateral Angle

• Forms the glenoid cavity.
• Articulates with the humerus to form the shoulder joint.

Processes

Spine of Scapula

• Divides dorsal surface.
• Triangular shape with three borders.
• Two surfaces: upper (supraspinous fossa) and lower (infraspinous fossa).

Acromion Process

• Projects from lateral end of the spine.
• Overhangs the glenoid cavity.
• Two borders (lateral and medial) and two surfaces (upper rough, lower smooth).

Coracoid Process

• Projects from above the glenoid cavity.
• Divided into ascending and horizontal parts.
• Horizontal part features: conoid tubercle and trapezoid ridge.

Determination of Side

• Glenoid cavity should face laterally and upwards.
• Spine should face backward.
• Inferior angle should face downward.
• Coracoid process should face forwards and laterally.

Ossification

• Enchondral (from cartilage) with eight centers (one primary, seven secondary).
• Primary center in the 8th week of intrauterine life, fuses at 15 years.
• Secondary centers: coracoid (1st year, fuses at 15 years), acromion, medial border, inferior angle, lower rim of glenoid cavity (appear around puberty, fuse by 20 years).
• Note: Failure to unite of acromion centers might appear as a fracture; check opposite acromion in radiographs.

Clinical Application

Congenital High Scapula (Sprengel's Deformity)

• Scapula develops in the neck and descends to the back of the chest.
• If descent fails, scapula remains in the neck region (hypoplastic).
• Possible fibrous tissue/cartilage/bone connection to the cervical vertebral column.
• Surgical correction may risk brachial plexus damage.