Immobilization of the mallet finger. Effects on the extensor tendon.

Since the mallet finger that is treated with isolated splinting of the distal interphalangeal (DIP) joint can be moved freely proximal to the DIP joint, we sought to determine whether such motion might cause a tendon gap that could explain the extensor lag that often follows treatment. Experiments were performed on 32 cadaveric fingers with open mallet finger lesions, immobilizing either the DIP joint alone or both the DIP and PIP joints, while repeatedly flexing and extending the more proximal finger and wrist joints. For each experiment, the gap in the extensor tendon was measured. Joint motion proximal to the DIP joint and retraction of the intrinsics did not cause a tendon gap in a finger with a mallet lesion, supporting the convention that only the DIP joint needs to be immobilized.