claw hand deformity

CLAW HAND DEFORMITY

Definition

It is a deformity with hyperextension of the metacarpophalangeal joints and flexion of the interphalangeal joints of the fingers.

Types and Causes

Two varieties are described: one is a true claw hand involving both median and ulnar nerves and the second an ulnar claw hand or claw-like hand due to ulnar nerve injury (Table 17.3).

Problems of claw hand

Hyperextension of MP joints (not the only primary or most disabling deformity).

Grasp decreased by 50 percent due to loss of power of flexion at MP joints.

Pinch decreased due to loss of stabilizing effect from the intrinsic.

Roll up maneuver lost.

Many surgical procedures are devised to block hyper extension of MP joints as it is still considered as the primary deformity.

Clinical Features

These include the classical deformity, loss of sensation along the ulnar nerve distribution and wasting of the hypothenar muscles, intrinsic muscles of the hand leading to hollow intermetacarpal spaces on the dorsum of the hand (Figs 17.6A to C) and causes ulnar claw hand.

A test for loss of sensation along the distribution (Fig. 17.7) of the ulnar nerve in the hand and fingers is carried out. However, the clinical features vary depending upon the level of lesion (Table 17.4).

Clinical Tests

For ulnar nerve injury

*Froment's sign (Fig. 17.8) This is a reliable clinical test for ulnar nerve injury. Three muscles (first palmar interossei,

adductor pollicis and flexor pollicis longus) are required to hold a book between the thumb and other fingers. In ulnar nerve injury the first two muscles are paralyzed and now to hold the book, patient has to depend only on flexor pollicis longus which flexes the thumb prominently. This is the positive Froment's sign.

Card test (Fig. 17.9): Inability to hold a card or paper in between fingers due to loss of adduction by the palmar interossei.

Fig. 17.9: Card test for ulnar

Egawa test (Fig. 17.10): With palm flat on the table the patient is asked to move the middle finger sideways. This is a test for the dorsal interossei of middle finger.

In total clawing median nerve is also injured. Following

tests will help to detect the median nerve injury.

For median nerve injury

Note Median nerve supplies the following muscles: In the forearm Pronator teres, flexor carpi radialis, palmaris longus, lexor digitorum superficialis, flexor digitorum profundus, rexor pollicis longus and pronator quadratus.

In the hand It supplies the abductor and flexor pollicis brevis, opponens pollicis brevis, lumbricals of the middle and index fingers.

Pen test (Fig. 17.11) Patient is unable to touch the the loss of action of abductor pollicis brevis. 

Pointing index or Oschner's clasp test (Fig. 17.12) When both the hands are clasped together, index and middle fingers, fail to flex due to the loss of action of long finger flexors of the index and middle fingers which are supplied by the median nerve.

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Benediction test (Fig. 17.23) For the same reason mentioned above patient is unable to fles the index and middle finger on lifting the hand (this is the position a clergyman uses to bless a couple during marriage. Hence, called benediction test).

What is ulnar paradox?

The higher the lesion of the median and ulnar nerve injury, the less prominent is the deformity and vice versa. This is because in higher lesions the long finger flexors are paralyzed. The loss of finger flexion makes the deformity look less obvious.

Investigations

Plain radiograph of affected area and other investigations like EMG, SD curve, nerve conduction studies, Tinel sign, etc. are carried out

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Trea

In acute injuries The treatment is as discussed in the general principles.

For Claw Hand Deformity

Principles of treatment All the treatment measures aim at blocking the hyperextension at the metacarpophalangeal joint. Once this joint is stabilized the long extensors will bring about the extension of IP joints. The long finger flexors will help in flexion of the MP joints along with their action of finger and wrist flexion.

Methods of Stabilization of MP Joints

This can be done by the active method which involves tendon transfer or by passive method which involves arthrodesis, capsulodesis or tetodists.

Active method This is by tendon transfers. A neighboring

healthy tendon is brought to replace the action of the lost intrinsic. The choice of the tendon is dictated by the available normal tendons and the existing local situations. Whichever the tendon chosen, it is passed through the lumbrical canal and is attached to the dorsal digital expansion which then brings about the action of the lost intrinsic. Before resorting to tendon transfers, certain criteria are to be followed (Table 17.5).