Restoration of prehension after severe mutilations of the hand.

We intend to discuss the injuries of the hand that disrupt the motor and sensory elements necessary for prehension. Prehension is a complex mechanism, for which both movement and sensation are required if it is to be fully effective, though sensation can to some extent be replaced by vision. Discussing normal function, Napier (1956) stressed the importance of making a distinction between the “ power grip “ and the “ precision grip,” and emphasised that the type of prehension was determined more by the objective intended in grasping than by the actual form of the object grasped. Landsmeer (1962) described these functions rather more dynamically as “ power grip “ and “ precision handling.” The whole pattern of precision gripping or handling is determined by the ability of the thumb to abduct and oppose. In the badly damaged hand an attempt should be made to reconstitute these different types of prehension, but it is often only possible to restore the basic grip necessary for pinch. This grip requires two opposing units, of which at least one must move and at least one should have sensibility. Anatomically, two basic types of simple grip can be described : the digital pinch, between thumb and finger tips; and the palmar grasp, in which the fingers hold an object against the palm. For digital pinch, the minimum required is a thumb, or a reconstructed thumb of nearly normal length, and a finger to which it can oppose. For palmar grasp, the hand wraps round the object being held : for this action mobile joints are necessary. The principal hinge joint movement takes place normally at the metacarpo-phalangeal joints: these joints control the locking and unlocking of “ grasp,” since they close after the interphalangeal joints during flexion of the fingers, and open before the interphalangeal joints during extension. If this hinge function is faulty the proximal interphalangeal joints can substitute for it. The strength of grasp of the whole hand depends on the breadth of the palm and on the degree of preservation of the peripheral parts of the fingers. The thumb is not essential for this grip, but it considerably increases the strength of grip and improves control. It is because of its influence on the strength of grip and its ability to oppose that the thumb constitutes such an