What deformity is associated with PIP hyperextension and DIP extension?

• A. Mallet finger
• B. Boutonnière deformity
• C. Swan neck deformity
• D. Jersey finger

Answer: (C)

The correct answer focuses on the distinguishing characteristics of the swan neck deformity. This deformity is characterized by a specific pattern of finger motion where the proximal interphalangeal (PIP) joint is hyperextended while the distal interphalangeal (DIP) joint is also extended. This creates a distinctive "swan neck" appearance that is easily recognizable.

In the context of the swan neck deformity, the underlying issue often relates to conditions such as rheumatoid arthritis, where there is an imbalance of the forces acting on the joints. The hyperextension at the PIP joint typically occurs due to the weakening or damage to the volar plate, while the extended position of the DIP joint is due to the resulting mechanical changes that occur in the tendon and ligament structure.

The other options present different types of finger deformities that do not display the combination of PIP hyperextension and DIP extension. For instance, mallet finger is characterized by DIP flexion due to a rupture of the extensor tendon, and boutonnière deformity shows PIP flexion with DIP extension. Jersey finger refers to a situation where the flexor tendon is ruptured, leading to the inability to flex the DIP joint. Thus, the characteristics of these other