Functional anatomy of the extensor tendons of the digits.

The complexity and intricacy of hand function are reflected by the anatomy. Extensor muscles have a relatively consistent architecture but also have notable anatomic variations of their tendons, particularly on the ulnar side of the hand. The extensor tendons, juncturae tendinum, intertendinous fascia, and soft tissue function as a plexiform construct to provide stability during power grip and allow for laxity in performing independent fine finger tasks. The greater independence of index finger motion relates to its two tendons, one (EDC-index) with a thin transverse juncturae tendinum, the other (EIP) without a junctural connection. It is also more independent because of a more mobile metatarsal, and because it is confined by only one web. The first dorsal interosseous also functions to rotate the index finger. The lumbrical to the index finger has only a single origin on the flexor profundus tendon. The elaborate tendon plexus on the dorsum of the hand is repeated in the complexity of the dorsal aponeurosis on the dorsum of the fingers. Finger motion is a balance of flexor muscles and intrinsics and extensor muscles that provides incredible versatility. This versatility and delicate balance of function is easily jeopardized by trauma and disease. The hand is among the most frequently injured parts of the body. An appreciation and understanding of its complex anatomy is of importance to hand assessment, repair, and reconstruction.