Extensor Tendon Injury

• Zones of Extensor Tendon Injuries (2):
  • Zone I – Mallet Finger - inability to extend at DIPJ due to terminal extensor tendon disruption (Mallet Finger).
  • Zone II (MP) – EPL disruption of middle/proximal phalanx of the thumb.
  • Zone III – Boutonniere deformity (swan neck) – central slip disruption over the digit PIPJ or MCPJ of thumb. This causes loss of extension at PIPJ and hyperextension at DIPJ.
    • Elson test: with finger over the edge of table and PIPJ flexed, ask the patient to extend at the PIPJ against resistance.
  • Zone IV – extensor tendon disruption over digit PIP or thumb MCP
  • Zone V (MCPJ) – Fight bite/Sagittal band Rupture (“boxer’s knuckle”) – extensor disruption over digit MCPJ or thumb CMCJ.
  • Zone VI (dorsum of hand) – disruption over MCP
  • Zone VII (wrist) – disruption at the wrist. Partial release of retinaculum is required in most cases to visualise the extensor tendons. Part of retinaculum has to be preserved to prevent bowstringing.
  • Zone VIII (forearm) – disruption at distal forearm often involving multiple extensor tendons.
• XR Hand (3)
  • AP, lateral and oblique (look for any signs of avulsion)

If an open extensor laceration present:

• Instruct patient NBM
• Check tetanus status
• Washout the wound with running water (consider LA if too painful to complete appropriately)
• Give pain relief and consider antibiotics (consult local antimicrobial guidelines)
• Apply suitable dressing (first layer non-adherent)
• If zone 5 or more proximal place in POP in Edinburgh position. Finger (zone 1-4) injuries can be splinted for comfort if necessary.
• High arm sling
• Consult and review XR with senior. Might need an urgent repair if neurovascularly unstable, otherwise place on trauma list and patient will be booked onto a CEPOD list.