Zone I contains only the FDP tendon and extends from the insertion of the FDP to the insertion of the FDS tendon.
Zone II is the area extending from the insertion of the FDS tendon to the distal palmar crease (proximal end of the A1 pulley). This area is also known as ‘No-Man’s land’, due to the shared flexor sheath and a higher risk of adhesions.
Zone III is the palm area from the distal palmar crease (proximal end of the A1 pulley) to the distal border of the transverse carpal ligament.
Zone IV is within the carpal tunnel.
Zone V is proximal to the carpal tunnel in the distal forearm.
Zone TI is from the insertion of the flexor pollicis longus (FPL) to the proximal part of the A2 pulley.
Zone TII is from the proximal part of the A2 pulley to the distal part of the A1 pulley.
Zone TIII is proximal to the A1 pulley as far as the carpal tunnel.
Extensor zone for the tendon injures tendon injuries are classified into eight zones
Zone I is the area over the DIP joint and distal phalanx. Disruption of the tendon will cause mallet finger. The long-term consequence of this injury can be a swan-neck deformity.
Zone II is over the middle phalanx; assessment and treatment are the same as for zone I injuries.
Zone III is over the PIP joint. Injury here can result in a boutonnière’s deformity, which is hyperextension at the MCP and DIP joints.
Zone IV injuries are located on the proximal phalanx and are treated like zone III injuries.
Zone V injuries occur over the MCP joint.
Zone VI injuries are on the dorsum of the hand. The tendons are very superficial here and can be easily damaged.
Zone VII injuries involve the wrist and multiple tendons; these should be evaluated by a hand surgeon.
Zone VIII injuries are in the distal forearm. Injuries in this location often require tendon retrieval for complete lacerations and may need to be performed in the operating room.
