Kinematics of the proximal interphalangeal joint of the finger after surface replacement

Nine fresh-frozen normal human cadaveric long fingers were used to corn pare the kinematics of the proximal interphalangeal joint (PIP) before and after a resurfacing metal-polyethylene prosthetic replacement (Avanta prosthesis, San Diego, CA) using the magnetic Isotrak system (Polhemus Navigational Systems, Colchester, VT). The kinematics of the PIP joint after replacement were similar to that of the normal joint. The maximum angular displacement was 5°for lateral deviation and 9°for rotation during the passive flexion and extension motion. The center of rotation after implant insertion was nearly identical to the center of rotation of the normal joint. This anatomically designed Pip prosthesis has potential to restore normal motion to the finger PIP joint while resisting physiologic out-of-plane forces such as pinch and grasp. (C) 2000 by the American Society for Surgery of the Hand.