College of Massage Therapists of British Columbia (CMTBC) Practice Exam

What is the primary mechanism behind Claw Fingers Deformity?

1. Loss of intrinsic muscle action

2. Overaction of flexor muscles

3. Damage to the extensor tendons

4. Over-recruitment of palmar muscles

The correct answer is: Loss of intrinsic muscle action

The primary mechanism behind Claw Fingers Deformity is the loss of intrinsic muscle action. This condition typically arises when the intrinsic muscles of the hand, particularly the interossei and lumbricals, are weakened or paralyzed. These intrinsic muscles play a crucial role in flexing the metacarpophalangeal joints while simultaneously extending the proximal and distal interphalangeal joints. When they are compromised, it results in an imbalance between the flexor and extensor forces acting on the fingers. Without the normal function of the intrinsic muscles, the extrinsic flexor muscles can pull the fingers into a flexed position at the metacarpophalangeal joints while leaving the interphalangeal joints extended, creating the characteristic "claw" appearance. This deformity is often seen in conditions such as ulnar nerve injuries, where the intrinsic muscles become weakened due to a lack of nerve supply. The other mechanisms listed do not accurately represent the primary cause of Claw Fingers. For instance, while overaction of flexor muscles and damage to the extensor tendons can contribute to hand dysfunction, they do not directly explain the specific presentation of Claw Fingers. Similarly, over-recruitment of palmar muscles does not correlate