Claw hand deformity involves which pattern?

Claw hand deformity involves which pattern?

• A. Hyperextension at DIP and PIP
• B. Hyperflexion at MCP and extension at IP
• C. Flexion at MCP and extension at IP
• D. Hyperextension at MCP and flexion at IP joints

Answer: (D)

Claw hand results from weakness of the intrinsic hand muscles (interossei and the lumbricals), typically due to ulnar nerve impairment. Those intrinsic muscles normally flex the metacarpophalangeal joints and extend the finger’s interphalangeal joints, balancing the action of the long extensors and flexors. When the intrinsic muscles are paralyzed, the extensor digitorum can pull the MCP joints into hyperextension, while the flexors (FDP/FDS) pull the IP joints into flexion because there’s no intrinsic to extend them. The net posture is hyperextension at the knuckles (MCP) with flexion at the finger joints (PIP/DIP), creating the claw appearance. This is distinct from other deformities, which involve different joint patterns.

Claw hand results from weakness of the intrinsic hand muscles (interossei and the lumbricals), typically due to ulnar nerve impairment. Those intrinsic muscles normally flex the metacarpophalangeal joints and extend the finger’s interphalangeal joints, balancing the action of the long extensors and flexors. When the intrinsic muscles are paralyzed, the extensor digitorum can pull the MCP joints into hyperextension, while the flexors (FDP/FDS) pull the IP joints into flexion because there’s no intrinsic to extend them. The net posture is hyperextension at the knuckles (MCP) with flexion at the finger joints (PIP/DIP), creating the claw appearance. This is distinct from other deformities, which involve different joint patterns.