Wrist Disarticulation Type. This apparently autosomal recessive trait is more common in females and is seldom bilateral. Typically, the stump is long, and skin nubbins represent failure of digit development. The epiphyses of the distal radius and ulna are present, but all skeletal elements distal to them are absent (see Plate 4-40). Pronation and supination capabilities usually exist, but a cartilaginous bar bridging the radius and ulna is occasionally present.

In patients with unilateral involvement, a forearm socket is molded to the dorsopalmar diameter of the stump to take advantage of pronation and supination capabilities. The terminal grasping device is activated by contralateral scapular abduction through a shoulder harness and cable-linkage system. With appropriate training, even young patients soon become proficient in the use of the prosthesis.

Patients with congenital bilateral absence of hands present a greater rehabilitation challenge because they lack tactile gnosis when wearing artificial limbs. The Krukenberg procedure splits the forearm stump into a prehensile forceps (see Plate 4-40). Providing the forearm stump is sufficiently long, the procedure can be used in blind patients with bilateral hand loss, in patients living in areas where prosthetic services are not available, and in any patients with bilateral hand loss. Using the simple mechanical principle of chopsticks, patients with a Krukenberg hand can function with amazing dexterity. The advantages of readily available prehension with sensation are theoretically significant; however, the Krukenberg procedure has not been shown to improve function in sighted patients. Thus, it is rarely indicated.

The goal of the procedure is to convert the forearm into a strong, active forceps with the radial ray opposing the ulnar ray. The muscles and tendons are divided between the radial and ulnar rays. The interosseous membrane is divided at the ulnar periosteal attachment, preserving the interosseous nerve and vessels. Tactile sensation should be present between the tips. Any digits present, with their associated vessels and tendons, are retained. The forceps should spread wide enough to accommodate ordinary objects, such as a drinking glass, and should be strong enough to hold common objects securely. If the forceps is too long, it may lack strength; if it is too short, distal spread may be insufficient. The pronator teres muscle limits the proximal depth of the forceps.

Patients with a Krukenberg hand begin a training program 2 to 3 weeks after surgery. They learn how to grasp and release rapidly. Pronation and supination are strong, natural movements, but patients must learn to abduct and adduct the forceps rays for best function. Moving the radius toward or away from the relatively fixed ulna provides the principal abduction-adduction motion. In strong gripping, however, ulnar adduction is also important. The therapist plays an essential role in teaching patients to use standard implements and perform two-handed activities, using a hook on the contralateral limb.