Answer :
Final answer:
Hyperextension of the PIP joint and flexion of the DIP joint, observed in rheumatoid arthritis patients, is referred to as Swan Neck Deformity. This should not be confused with Boutonniere Deformity, Mallet Finger, or Jersey Finger, each of which presents with different joint involvements or injuries.
Explanation:
The Swan Neck Deformity is characterized by hyperextension of the PIP (proximal interphalangeal) joint and flexion of the DIP (distal interphalangeal) joint. This condition is often seen in patients with rheumatoid arthritis (RA). The deformity results from imbalances in the muscles and tendons that control the movements of the finger joints. Specifically, the palmar interossei muscles are instrumental in flexing the fingers at the metacarpophalangeal joints and extending them at the interphalangeal joints.
The Boutonniere Deformity, on the other hand, is represented by flexion of the PIP joint and hyperextension of the DIP joint. This deformity can also occur in RA patients but represents a different pattern of joint involvement compared to the Swan Neck Deformity.
A Mallet Finger is the result of an injury to the extensor tendon at the DIP joint, leading to an inability to extend the fingertip. A Jersey Finger occurs when there is an avulsion of the flexor tendon from the insertion on the distal phalanx, typically caused by a forceful extension of a flexed finger.
In this case, the correct answer for the deformity described (fixed flexion of the DIP with hyperextension of PIP) is a) Swan Neck Deformity.
