Abstract: To study the flexion deformity after surgical treatment for metacarpal and phalangeal fractures, from January 2003 to December 2007, 128 outpatients suffered from metacarpal and phalangeal fractures were chosen in this paper. All of the fractures were fixed with Kirschner wires. Among them, 25 cases are of metacarpal fractures, 37 cases of proximal phalanx fractures, 42 cases of middle phalanx fractures, and 24 cases of multiple fractures. All of the fractures, of which 38 cases of closed fractures and 90 cases of open fractures, were fixed with cross or oblique Kirschner wires. All the Kirschner wires did not go through the joints. After the operation, plasters were used for 3 to 4 weeks, 53 of which in flexion position and 75 in extension position. The Kirschner wires were taken out 4 to 15 weeks after the operation. The results show that 19 cases of proximal interphalangeal joint flexion deformity were found (15%). The Flexion position is usually used in Kirschner wire fixation of metacarpal, phalangeal fractures to avoid the skin stimulation of the tail of Kirschner wire. The damage of the dorsal fascia might be responsible to flexion deformity.