Extensor expansion

Extensor expansion‏‎, also known as the extensor hood, is a special type of anatomical structure found in the hand. It is a complex arrangement of tendons and muscles that allows for the extension of the fingers and thumb.

Anatomy

The extensor expansion is formed by the convergence of the tendons of the extensor digitorum muscle, the extensor indicis muscle, and the extensor digiti minimi muscle. These tendons spread out over the back of the fingers and thumb, forming a broad, flat structure that is often likened to a hood.

The extensor expansion is attached to the phalanx bones of the fingers and thumb. It is divided into three parts: a central part, which is attached to the middle phalanx; and two lateral parts, which are attached to the base of the distal phalanx.

Function

The primary function of the extensor expansion is to extend the fingers and thumb. This is achieved through the contraction of the extensor muscles, which pull on the extensor expansion and cause the fingers and thumb to straighten.

In addition to extension, the extensor expansion also allows for some degree of abduction (movement away from the midline of the body) and adduction (movement towards the midline of the body) of the fingers and thumb.

Clinical significance

Damage to the extensor expansion can result in a loss of finger and thumb extension. This can occur as a result of trauma, infection, or rheumatoid arthritis. Treatment typically involves physiotherapy and, in severe cases, surgery.

See also

• Hand anatomy
• Extensor muscles of the hand
• Tendon
• Muscle