Answer :
Final answer:
Boutonniere deformity is characterized by persistent flexion of the PIP joint with hyperextension of the DIP joint, involving the mechanics of the palmar interossei muscles and metacarpophalangeal joints.
Explanation:
The condition described by the student where there is persistent flexion of the Proximal Interphalangeal (PIP) joint with hyperextension of the Distal Interphalangeal (DIP) joint is known as Boutonniere deformity. The palmar interossei muscles are responsible for the flexion at the metacarpophalangeal joints, while the extension is controlled at the interphalangeal joints. When these mechanics are disrupted, deformities such as Boutonniere can occur. The metacarpophalangeal joints mentioned are examples of condyloid joints, which allow for the range of motion necessary for flexing and extending the fingers. Understanding how these joints and muscles work together is crucial in diagnosing and treating such deformities.
