The proximal interphalangeal joint of finger is important structure in hand function and injury to this joint may result in stiffness, chronic instabilitiy and degenerative arthritis, especially if it is recognized later or treated improperly. The Compass PIP(proximal interphalangeal joint) Hinge is a dynamic external fixator that allows protected proximal interphalangeal mobilization after closed reduction, open reduction and internal fixation, volar plate arthroplasty, or other salvage procedures. It is important to get the congruence of articular surface and singular point that is the center of axis of the proximal interphalangeal joint for good result. We report two cases which show satisfactory result using this device. The first case was 23 year-old male who complains of limitation of motion of the proximal interphalangeal(PIP) joint of right index finger. He got hyperextension injury of PIP joint about 3 months ago and
found that there was avulsion fracture of proximal phalanx base of index finger. He was treated open reduction and internal fixation and immobilized for 4 weeks and received physiotherapy after that period. Initial range of motion of PIP joint was flexion 20¡Æ, extension 0¡Æ. Six month after arthrolysis and PIP hinge external fixation, flexion and extension was improved to 100¡Æ, 0¡Æ respectively. The second case was 25 year-old male who visited to our hospital due to nonunion of middle phalax of right index finger after crushing injury. He received internal fixation and autoiliac bone graft. After 3 month, union was gained but stiffnes of PIP joint was remained. Initial range of motion of PIP joint was flexion 10¡Æ, extension 0¡Æ. One year after arthrolysis and PIP hinged device operation, the range of motion was improved to flexion 90¡Æ, extension -10¡Æ.