Interosseous membrane of forearm

At a glance

English

Interosseous membrane of forearm

Latin (TA2)

Membrana interossea antebrachii

System

Ligament

Region

Upper limb

Side

Paired, left and right

About the interosseous membrane of forearm

The two bones of the forearm are linked along most of their length by a tough fibrous sheet, the interosseous membrane. It spans the sharp facing edges of the two bones and is the chief element of the radio-ulnar syndesmosis, which works alongside the proximal and distal radio-ulnar synovial joints.

The membrane begins a few centimetres below the radial tuberosity and reaches down to the distal radio-ulnar joint. Most of its fibres run obliquely downwards and medially from the radius to the ulna. Above the upper edge is a gap through which the posterior interosseous vessels pass to the back of the forearm, and higher still a separate small band, the oblique cord, runs the opposite way from the ulnar tuberosity to just below the radial tuberosity. Near the lower end the anterior interosseous vessels pierce the membrane to reach the back. Detailed studies describe it as a set of distinct bands: a thick central band, an accessory band, a distal oblique bundle, a proximal oblique cord and a dorsal oblique accessory cord.

The membrane has three main jobs. It separates the flexor compartment in front from the extensor compartment behind and gives attachment to deep muscles of both, such as flexor pollicis longus and flexor digitorum profundus in front and abductor pollicis longus and the thumb extensors behind. It also transmits force. A push on the hand, as in a handstand or a fall, is taken first by the radius at the wrist; the oblique fibres tighten and pass much of that load across to the ulna, which carries it to the humerus at the elbow. Cutting the membrane experimentally evens out the loads on the two bones. Tension in the membrane varies with rotation, being greatest in the mid-position between pronation and supination and less at either extreme.

In a high-energy injury the membrane can rupture together with a fracture of the radial head, letting the radius migrate upwards and making the ulna seem too long at the wrist, the Essex-Lopresti lesion. Rotation of the forearm is often impaired after such tears. MRI and, more cheaply, ultrasound can show the damage, and reconstruction of the central band may be needed.

Attachments and function

Attaches from

The interosseous border of the radius.

Attaches to

The interosseous border of the ulna.

Function

Binds the radius to the ulna, separates the anterior and posterior compartments, gives attachment to deep forearm muscles and transfers load from the radius to the ulna.

Nerve supply

Branches of the anterior and posterior interosseous nerves lie on and supply it.

Blood supply

The anterior and posterior interosseous arteries, which run on its two surfaces.