Which deformity results from central slip injury to the extensor mechanism?

Study for the NBCOT Hand Injuries and Intervention Test. Prepare with flashcards and multiple choice questions, each question offers hints and explanations. Get ready for success!

Multiple Choice

Which deformity results from central slip injury to the extensor mechanism?

Injury to the central slip of the extensor mechanism disrupts the PIP joint’s ability to straighten. The central slip normally extends the PIP, but when it’s torn, the PIP joint flexes. The lateral bands then drift and pull the distal phalanx into extension, producing a finger posture with a flexed PIP and an extended (often hyperextended) DIP. This classic pattern is Boutonnière deformity. Understanding this helps distinguish it from other deformities: mallet finger comes from injury to the distal extensor tendon causing DIP flexion; swan neck deformity features PIP hyperextension with DIP flexion due to imbalance in the extensor mechanism and ligaments; Z deformity is a zig-zag pattern from Dupuytren’s contracture.

Injury to the central slip of the extensor mechanism disrupts the PIP joint’s ability to straighten. The central slip normally extends the PIP, but when it’s torn, the PIP joint flexes. The lateral bands then drift and pull the distal phalanx into extension, producing a finger posture with a flexed PIP and an extended (often hyperextended) DIP. This classic pattern is Boutonnière deformity.

Understanding this helps distinguish it from other deformities: mallet finger comes from injury to the distal extensor tendon causing DIP flexion; swan neck deformity features PIP hyperextension with DIP flexion due to imbalance in the extensor mechanism and ligaments; Z deformity is a zig-zag pattern from Dupuytren’s contracture.

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