In a patient with a peripheral nerve injury to the ulnar nerve at the wrist, which MCP joint position is recommended for splinting?

• A. Splint the interphalangeal joints in extension
• B. Splint the interphalangeal joints in flexion
• C. Splint the metacarpophalangeal joints in extension
• D. Splint the metacarpophalangeal joints in flexion

Answer: (D)

When the ulnar nerve is injured at the wrist, the intrinsic hand muscles (interossei and the medial lumbricals) are weakened or paralyzed. This leaves the extensor mechanism unopposed at the MCP joints, causing the fingers to drift into MCP hyperextension while the IP joints tend to flex—a claw-like posture. Positioning the MCP joints in slight flexion with a splint counteracts this imbalance, reducing MCP hyperextension and helping the fingers maintain a more functional alignment. Placing the IP joints in other positions does not address the main issue—the unopposed extension at the MCP joints—and would not prevent the clawing pattern. Therefore, splinting the MCP joints in flexion is the best approach.