What characterizes a claw hand deformity?

A claw hand deformity is characterized by a specific position of the hand where the fingers are hyperextended at the metacarpophalangeal (MCP) joints while simultaneously being flexed at the proximal interphalangeal (PIP) joints. This results in the appearance of a 'claw,' hence the name.

The position of the wrist can vary, but it typically involves some degree of wrist flexion, which further accentuates the hyperextension of the MCPs and flexion at the PIPs. This is commonly seen in conditions affecting the ulnar nerve, which innervates the intrinsic muscles of the hand responsible for finger positioning. Thus, option A accurately describes the characteristic presentation of a claw hand deformity.

Other options describe different positions of the hand which do not correspond to the typical presentation of a claw hand deformity. Extended wrist and flexed fingers, for example, would suggest a different pathology or deformity, while complete finger paralysis would indicate a total loss of function, which is not representative of claw hand where there is still some degree of active deformity present.