If the ulnar nerve is damaged at the tunnel of Guyon, which hand posture best describes the presentation?

If the ulnar nerve is damaged at the tunnel of Guyon, which hand posture best describes the presentation?

• A. Flexor digitorum profundus weakness causing hyperextension of the fourth and fifth MCP joints
• B. Wrist flexion with MCP flexion and PIP/DIP extension in an intrinsic plus position
• C. The hand will be resting in wrist flexion, MCP extension, and PIP/DIP flexion
• D. The wrist and first and second MCP, PIP, and DIP joints will be in an extended position

Answer: (C)

Damage to the ulnar nerve at the tunnel of Guyon removes the function of the intrinsic hand muscles (interossei, the deep head of the flexor pollicis brevis, adductor pollicis, and most of the lumbricals) plus the flexor carpi ulnaris. Without these intrinsic muscles, the hand assumes the classic “intrinsic minus” posture: the extensor digitorum can pull the metacarpophalangeal (MCP) joints of the ring and little fingers into extension, while the flexors (FDP/FDS) still pull the finger joints into flexion at the proximal and distal interphalangeal joints. The resulting posture includes MCP joints extended and PIP/DIP joints flexed in the affected digits, with the wrist often held in flexion due to paralysis of the FCU. This combination best matches a hand resting with the wrist flexed, MCPs extended, and PIP/DIP flexed.

Damage to the ulnar nerve at the tunnel of Guyon removes the function of the intrinsic hand muscles (interossei, the deep head of the flexor pollicis brevis, adductor pollicis, and most of the lumbricals) plus the flexor carpi ulnaris. Without these intrinsic muscles, the hand assumes the classic “intrinsic minus” posture: the extensor digitorum can pull the metacarpophalangeal (MCP) joints of the ring and little fingers into extension, while the flexors (FDP/FDS) still pull the finger joints into flexion at the proximal and distal interphalangeal joints. The resulting posture includes MCP joints extended and PIP/DIP joints flexed in the affected digits, with the wrist often held in flexion due to paralysis of the FCU. This combination best matches a hand resting with the wrist flexed, MCPs extended, and PIP/DIP flexed.