What sign is characteristic of Ape Hand Deformity?

The characteristic sign of Ape Hand Deformity is the loss of thumb opposition. This condition typically results from median nerve dysfunction, which affects the muscles responsible for controlling thumb movement, particularly the opponens pollicis muscle. When opposition is lost, the thumb is immobilized in a position that is aligned parallel to the fingers, making it difficult for the individual to grip or pinch objects. This inability to bring the thumb across the palm is a defining feature of Ape Hand Deformity, distinguishing it from other hand conditions.

The other options, while they may describe different symptoms or effects related to hand or nerve conditions, do not specifically encapsulate the hallmark of Ape Hand Deformity. For instance, inability to flex the wrist pertains more to overall wrist function rather than specifically addressing thumb movement. Hyperextension of the fingers is often seen in various conditions but does not accurately represent the unique presentation of this deformity. Swelling of the hand can occur in many different injuries or inflammatory conditions but again does not relate directly to the loss of thumb opposition that defines the Ape Hand Deformity.