Posterior surface of scapula

The posterior surface of scapula presents several key anatomical features crucial for understanding shoulder function:

1. Spine of the Scapula

This prominent transverse ridge divides the posterior surface into the supraspinous fossa above and the infraspinous fossa below. It serves as a vital attachment point for the trapezius and deltoid muscles.

2. Acromion

Extending laterally from the spine, the acromion forms the superior-most bony prominence of the shoulder. It articulates with the clavicle at the acromioclavicular (AC) joint and provides attachments for portions of the deltoid and trapezius muscles.

3. Supraspinous Fossa

This shallow depression, situated superior to the scapular spine, is the origin of the supraspinatus muscle. As one of the four rotator cuff muscles, the supraspinatus plays a critical role in the initial phases of arm abduction.

4. Infraspinous Fossa

Located inferior to the scapular spine, this larger depression provides the origin for the infraspinatus muscle, another key rotator cuff muscle responsible for external rotation of the humerus.

5. Spinoglenoid Notch

Found at the lateral aspect of the scapular spine, near its junction with the glenoid cavity, this notch serves as a passageway for the suprascapular nerve and vessels as they course from the supraspinous to the infraspinous fossa, supplying the supraspinatus and infraspinatus muscles respectively.

6. Medial Border

This vertebral border runs parallel to the spinal column and provides a linear attachment for the levator scapulae, rhomboid major, and rhomboid minor muscles. These muscles are essential for scapular retraction (adduction) and contribute to scapular stability.

7. Lateral Border

Extending from the inferior angle of the scapula superiorly to the glenoid cavity, this axillary border serves as the attachment site for the teres major and teres minor muscles. The teres minor, a rotator cuff muscle, assists in external rotation, while the teres major contributes to arm adduction and internal rotation.