Posterior compartment of forearm

The posterior compartment of forearm, also known as the extensor compartment, houses the muscles primarily responsible for extension of the wrist and fingers. These muscles are organized into two distinct layers:

Superficial layer

The muscles of the superficial layer typically originate from the lateral epicondyle of the humerus and the adjacent supracondylar ridge of the humerus. These include:

• Brachioradialis

• Extensor carpi radialis longus

• Extensor carpi radialis brevis

• Extensor digitorum

• Extensor digiti minimi

• Extensor carpi ulnaris

• Anconeus

Deep layer

The deep layer muscles typically originate from the adjacent surfaces of the radius, ulna, and interosseous membrane. They include:

• Abductor pollicis longus

• Extensor pollicis brevis

• Extensor pollicis longus

• Extensor indicis

• Supinator

The tendons of many of these muscles pass beneath the extensor retinaculum at the wrist to reach the dorsal aspect of the hand and digits.

Innervation

The muscles of the posterior compartment of forearm are primarily innervated by the posterior interosseous nerve, which is a continuation of the deep branch of the radial nerve. Notable exceptions are the brachioradialis and extensor carpi radialis longus, which receive their innervation directly from the radial nerve before its bifurcation into superficial and deep branches.

Vasculature

The main vascular supply to this compartment is provided by the posterior interosseous artery. This artery branches from the common interosseous artery (a branch of the ulnar artery) and travels alongside the posterior interosseus nerve along the interosseous membrane.