Which of the following is seen in Boutonniere’s deformity:
**Core Concept**
Boutonniere's deformity is a flexion deformity of the proximal interphalangeal (PIP) joint, resulting from a disruption of the extensor tendon mechanism. This condition is characterized by a flexion contracture of the PIP joint, with the distal interphalangeal (DIP) joint being hyperextended.
**Why the Correct Answer is Right**
The key feature of Boutonniere's deformity is the rupture of the central slip of the extensor tendon, leading to the characteristic flexion deformity of the PIP joint. This occurs due to a traumatic injury or inflammatory conditions such as rheumatoid arthritis. As a result, the extensor tendon is no longer able to extend the PIP joint, causing it to flex.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not describe the characteristic flexion deformity of the PIP joint seen in Boutonniere's deformity.
**Option B:** This option is incorrect because it refers to a different condition, Dupuytren's contracture, which affects the palmar fascia and causes a flexion deformity of the fingers at the MCP joints.
**Option C:** This option is incorrect because it refers to a condition that affects the thumb, known as "gamekeeper's thumb," which is caused by a disruption of the ulnar collateral ligament.
**Clinical Pearl / High-Yield Fact**
Remember that Boutonniere's deformity is often associated with a "sagging string" sign, where the extensor tendon appears to be hanging from the proximal phalanx, due to the rupture of the central slip.
**Correct Answer:** C.