Which statement is true about deep branch ulnar nerve injury?

• A. It causes intrinsic minus posture
• B. It causes carpal tunnel syndrome
• C. It causes radial deviation
• D. It causes median nerve palsy

Answer: (A)

Deep branch injury of the ulnar nerve disrupts the intrinsic muscles of the hand—the interossei, the medial two lumbricals, the hypothenar group, and the adductor pollicis. When these muscles are paralyzed, the intrinsic balance that normally flexes the MCP joints and extends the IP joints is lost, so the extensor muscles pull the MCP joints into extension while the IP joints become flexed. This combination produces the intrinsic minus posture (often described as clawing) of the hand.

Carpal tunnel syndrome is a problem of the median nerve at the wrist, not the ulnar intrinsic muscles. Radial deviation points to issues with the radial side nerves or extensors, not deep branch ulnar involvement, and does not reflect loss of intrinsic hand function. Median nerve palsy involves different muscles and patterns of weakness. Therefore, the true statement is that deep branch ulnar nerve injury causes intrinsic minus posture.