Anatomical Basis of Claw Hand

Definition and Clinical Presentation

Claw hand is a condition characterized by the hyperextension of the metacarpophalangeal (MCP) joints and flexion of the interphalangeal (IP) joints, typically affecting the fourth and fifth fingers. This deformity arises due to an imbalance between the intrinsic and extrinsic muscles of the hand, often caused by ulnar nerve dysfunction.

Anatomical Basis

Ulnar Nerve Involvement

The ulnar nerve innervates most of the intrinsic muscles of the hand, including the lumbricals of the fourth and fifth digits and the interosseous muscles. Damage to this nerve leads to the unopposed action of the extrinsic flexors and extensors, resulting in the characteristic claw-like appearance.

Muscle Imbalance

• Loss of lumbrical function leads to excessive extension at the MCP joints.
• Unopposed action of the flexor digitorum profundus results in flexion at the IP joints.
• Weakness in interosseous muscles further exacerbates the deformity.

Clinical Features

• Hyperextension of MCP joints and flexion at IP joints.
• Loss of fine motor skills, especially in grip strength.
• Atrophy of the hypothenar eminence.
• Positive Froment’s sign due to weakened adductor pollicis.

Causes

• Ulnar nerve injury due to trauma or compression.
• Leprosy affecting peripheral nerves.
• Diabetic neuropathy.
• Congenital conditions such as Klumpke’s palsy.

Treatment Options

Management of claw hand depends on the underlying cause. Common treatment strategies include:

• Physical therapy for muscle strengthening.
• Splinting to maintain proper hand posture.
• Surgical interventions such as tendon transfer.
• Nerve repair or grafting in severe cases.