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

Which hand deformity is characterized by MCP flexion, PIP hyper-extension, and DIP flexion?

1. Drop hand deformity

2. Swan Neck deformity

3. Boutonnière deformity

4. Ulnar drift

The correct answer is: Swan Neck deformity

The hand deformity characterized by metacarpophalangeal (MCP) flexion, proximal interphalangeal (PIP) hyper-extension, and distal interphalangeal (DIP) flexion is known as Swan Neck deformity. In this condition, the positioning of the fingers is the result of a disruption in the normal balance of the flexor and extensor tensions. Typically, the flexor digitorum superficialis and flexor digitorum profundus may become diminished or their function impaired, leading to the extension at the PIP joint while the DIP joint flexes, creating a characteristic "Swan Neck" appearance. This deformity can often be associated with various conditions, such as rheumatoid arthritis, where joint instability and altered muscle balance can affect finger positioning. Understanding this, one can differentiate it from other conditions: Drop hand deformity involves an inability to extend the fingers at all, Boutonnière deformity is characterized by PIP flexion and DIP extension, and ulnar drift refers to the deviation of the fingers towards the ulnar side at the MCP joints, without the specific flexion and extension pattern seen in Swan Neck deformity.