Bones - Scapula

Question 1

What is the general location of the scapula?

What does it articulate with?

Answer 1

The triangular-shaped scapula, also known as the shoulder blade, is located on the back.

It articulates with the humerus at the glenohumeral joint, and with the clavicle at the acromioclavicular joint. In doing so, the scapular connects the upper limb to the trunk.

Question 2

Anterior (costal) surface of the scapula

Bony landmarks?

What muscles are associated with these landmarks?

Answer 2

1) Subscapular fossa - large concave depression over most of its surface - the subscapularis originates from this fossa.
2) Coracoid process - originating from the superolateral surface of the costal scapula. It is a hook like projection, lying underneath the clavicle. The following muscles attach to the coracoid process:
1) Pectoralis minor
2) Coracobrachialis
3) Short head of the biceps brachii.

Question 3

What are the features of the lateral surface of the scapula?

Answer 3

This surface faces the humerus and is the site of the glenohumeral joint, and a site of various muscle attachments. Its bony land marks include:

1) Glenoid fossa - a shallow cavity, located superiorly on the lateral border. It articulates with the head of the humerus to form the glenohumeral joint.
2) Supraglenoid tubercle - a roughening immediately superior to the glenoid fossa. This is the place of attachment of the long head of the biceps brachii.
3) Infraglenoid tubercle - A roughening immediately inferior to the glenoid fossa. This is the place of attachment for the long head of the triceps brachii.

Question 4

What are the features of the posterior surface of the scapula?

Answer 4

This is the site of origin for the majority of the rotator cuff muscles of the shoulder. There are a number of bony landmarks:

1) Spine - runs transversely across the scapula, dividing the surface into two.
2) Acromion - projection of the spine that arches over the glenohumeral joint. It articulates with the clavicle at the acromioclavicular joint.
3) Infraspinous fossa - area below the spine of the scapula, it displays a covex shape. The infraspinatus originates here.
4) Supraspinous fossa - the area above the spine of the scapula - it is much smaller than the infraspinous fossa and more convex in shape. The supraspinatus muscle originates from this area.

Question 5

What are the articulations of the scapula?

Answer 5

1) Glenohumeral joint - between the glenoid fossa and the head of the humerus.
2) Acromioclavicular joint - between the acromion of the scapula and the clavicle.

Question 6

Clinical relevance - Fracture of the scapula

Aetiology?

Answer 6

These are relatively uncommon.

If they do occur, it is an indication of severe chest trauma. They are frequently seen in high speed RTAs, crushing injuries, or sports injuries.

Does not usually require fixation as the tone of the surrounding muscles holds the pieces in places for healing to occur.

Question 7

Clinical relevance - Winging of the scapula

Associated muscle and nerve?

Aetiology?

Answer 7

The serratus anterior muscle originates from ribs 1-8 and attaches to the costal surface of the scapula, pulling it against the ribcage.

The long thoracic nerve innervates the serratus anterior. If this nerve becomes damaged, the scapula protrudes out of the back when pushing with the arm.

The long thoracic nerve can become damaged by trauma to the shoulder, repetitive movements involves shoulder or by structures becoming inflamed and pressing on the nerve.