Surgery on the hand and forearm is generally performed using nerve-block anesthesia. Tourniquet ischemia is helpful to produce a bloodless field in which structures can be dissected accurately. Prepare the entire hand and all fingers and drape it free, allowing it to rest on an operating arm board.

Plan an incision that zigzags along the volar digital surface (Fig. 40.2A). This incision affords excellent exposure while minimizing problems secondary to wound contracture. It may be possible to make such an incision by extending the original laceration, after debriding the edges.

This incision provides excellent exposure and is not attended by problems associated with contracture. Laterally; however, care must be taken to avoid the palmar digital neurovascular bundles (the dorsal arteries are insignificant). These bundles lie along the sides of the digital flexor sheaths, not along bone. Of the three components of the neurovascular bundle, the nerve is most palmar, and the vein is most dorsal.

The anterior (palmar) and medial aspects of the forearm, wrist, and hand include muscles and tendons involved with flexion of the extremity (Fig. 40.2B). One muscle, the palmaris longus, attaches to the palmar aponeurosis, and its tendon is superficial to the middle of the flexor retinaculum. Two muscles in the anterior compartment—the pronator teres and pronator quadratus muscles—are concerned solely with rotation of the radius relative to the ulna and, hence, do not extend into the wrist and hand region. Two other muscles—flexor carpi radialis and ulnaris—are powerful flexors that likewise do not flex into the hand and have no components that pass through the carpal tunnel. Three additional muscles are concerned with flexion of the digits, and all components of these muscles pass through the carpal tunnel. Two of these—flexor digitorum superficialis and profundus—each divide into four tendons that provide flexion of digits 2 to 5. The final function of the muscle, the long flexor muscle of the thumb, is solely flexion of the thumb (digit 1). Because flexor tendon injuries most often involve digital flexors, the following anatomic description will be limited to these muscles and their relationships.