EFFECT OF WRIST POSITION ON EXTENSOR MECHANISM AFTER DISRUPTION SEPARATION

A cadaveric study was performed on extensor tendon separation and excu rsion after extensor zone I (distal interphalangeal [DIP]) joint and I II (proximal interphalangeal [PIP]) level lacerations and treatment. A n average 1.5 mm tendon gap with 30 degrees lag following laceration a t the DIP joint level and a 1.1 mm average tendon gap with 18 degrees (10 degrees-25 degrees) extension loss at the PIP level was demonstrat ed. Splinting zone I injuries with the DIP joints in 5 degrees hyperex tension and zone III injuries with the PIP joint in 0 degrees extensio n eliminated tendon separation in all passive joint positions except w hen the wrist and metacarpophalangeal joints were placed in flexion. T his position produced a 0.9 mm gap with a laceration at the DIP level and 1.0 and 2.0 mm gap at the PIP level, with a central slip and centr al slip and lateral band laceration, respectively. The tendon gaps wer e eliminated by placing the wrist in extension. This suggests that spl inting of the wrist in neutral to mild extension and the joint underly ing the tendon injury in full extension, while leaving the other joint s free to move, would optimize treatment results.