Peripheral Nerve Injuries: Claw Hand - Mechanism, Affected Nerves, and Rehabilitation

Claw hand is a clinical deformity characterized by hyperextension of the metacarpophalangeal (MCP) joints and flexion of the interphalangeal joints. This condition occurs due to nerve injuries that impair intrinsic hand muscle function.

Mechanism of Claw Hand

Claw hand results primarily from the dysfunction of the ulnar nerve and sometimes involves the median nerve. The intrinsic muscles of the hand, mainly the lumbricals and interossei, lose their ability to flex the MCP joints and extend the interphalangeal joints.

Affected Nerves

• Ulnar Nerve: Damage to the ulnar nerve leads to paralysis of most intrinsic muscles, especially the lumbricals of the fourth and fifth fingers, resulting in the claw hand deformity.
• Median Nerve: In severe cases, median nerve injury can also contribute by affecting the lumbricals of the second and third fingers.

Clinical Presentation

Patients with claw hand typically exhibit:

• Hyperextension of MCP joints
• Flexion of proximal and distal interphalangeal joints
• Weak grip strength
• Muscle atrophy in the hand

Rehabilitation and Treatment

Treatment aims to restore function and prevent contractures:

• Physical Therapy: Exercises to strengthen remaining muscles and improve mobility.
• Splinting: Functional splints to maintain finger positioning.
• Surgical Interventions: Tendon transfers or nerve repair procedures in severe cases.

Conclusion

Claw hand is a debilitating condition requiring prompt intervention and rehabilitation. Understanding its mechanism and affected nerves helps in effective management.