Zones
Extensor tendon injuries are described by zones from fingertip proximally.
- Zone I — DIP joint
- Zone II — middle phalanx
- Zone III — PIP joint
- Zone IV — proximal phalanx
- Zone V — MCP joint
- Zone VI — dorsum of hand
- Zone VII — wrist / extensor retinaculum
- Zone VIII — distal forearm
The thumb is described separately using corresponding thumb zones.
Important injuries
Zone I — mallet finger
Terminal extensor tendon disruption produces DIP flexion deformity.
Zone III — central slip injury
Can progress to boutonnière deformity.
Zone V
Consider a human bite or “fight bite” when there is a dorsal MCP wound.
Examination
Test each joint against resistance and assess tenodesis. Inspect for open injury and rotational deformity.
Treatment principles
- closed mallet injuries are usually splinted continuously in DIP extension
- open tendon injuries require appropriate wound management and repair depending on zone
- central slip injuries require early recognition and appropriate PIP extension splintage or repair
Diagram
