Ulna

The ulnais a long boneone of the forearm which acts as a stabiliser and transmitting force fromtwo long bones of the distal upper limb toforearm; it is located medially in the humerussupinated anatomic position. It has a larger proximal end and tapers to a smaller distal end (opposite to the radius). 

Gross anatomy

Prominent features of the ulna include:

• proximal: olecranon, trochlear notch, coronoid process, radial notch (lateral), sublime tubercle (medial)
• shaft: ulnar tuberosity
• distal: head, styloid process, groove for extensor carpi ulnaris

Articulations

• proximal: elbow joint (ulnatrochlear and proximal radioulnar joints)
• distal: distal radioulnar joint and wrist via the TFCC

Attachments

Musculotendinous

Anteriorly

• proximal: brachialis (to ulnar tuberosity), pronator teres (ulnar head), flexor digitorum superficialis (ulnar head)
• shaft: supinator, flexor digitorum profundus, pronator quadratus

Posteriorly

• triceps, aconeus, supinator, flexor digitorum profundus, flexor carpi ulnaris (ulnar head), extensor carpi ulnaris (ulnar head), abductor pollicis longus, extensor pollicis longus, extensor indices, 

Ligamentous

• proximal: medial collateral ligaments of the elbow (anterior, posterior, and middle bands), anterior and posterior capsular ligaments of the elbow
• medial: anterior and posterior attachments of the annular ligament, quadrate ligament, oblique cord, interosseus membrane
• distal: triangular fibrocartilage, ulnar collateral ligament of of the wrist

Relations and/or boundaries

The ulna and its attachments help to divide the forearm into anterior and posterior compartments. 

Its subcutaneous border lies postero-medially and the antebrachial fascia attaches on either end. 

Its interosseus border (anterolaterally) is attached to the interosseus membrane of the forearm.

Blood supply

The forearm (and ulna) is supplied by the ulnar artery and its continuation as the common interosseus artery with the anterior and posterior interosseus branches.

Nerve supply

Periosteum is supplied anteriorly by the anterior interosseus nerve (branch of median nerve).

Posteriorly, the periosteum is supplied by the posterior interosseus nerve (branch of radial nerve)

Lymphatic supply

Lymphatics of the hand and forearm drain either to the supratrochlear lymph node, or directly into the lateral group of axillary lymph nodes.

Radiographic features

Carrying angle of 15-20 degrees. Increased in females.

Development

Intracartilagenous ossification begins in utero. Ossification centres include:

• shaft/diaphysis (8 weeks gestation)
• distal (5-7 years > 16-18 years)
• proximal (8-10 years > 13-15 years)

Related Pathology

• Monteggia fracture: fracture of ulna with dislocation of proximal radioulnar joint
• Madelung deformity