METACARPAL SHAFT FRACTURES - THE EFFECT OF SHORTENING ON THE EXTENSORTENDON MECHANISM

Spiral and oblique metacarpal shaft fractures frequently develop short ening through the fracture site. The acceptable amount of fracture sho rtening has not been well established. The goal of this study was to e lucidate the acceptable limits of metacarpal shaft fracture shortening in a cadaver model by assessing the magnitude of the metacarpophalang eal (MCP) joint extensor lag produced. Nine fresh-frozen cadaver hands were used to create a metacarpal shaft fracture model in the second a nd fifth metacarpal bones. Sequential shortening up to 10 mm in 2-mm i ncrements was performed. The results revealed an average of 7 degrees of extensor lag at the MCP joint produced for every 2 mm of metacarpal shortening. The capacity of the MCP joint for active hyperextension m ay compensate for the extensor lag produced by metacarpal shortening i n the clinical setting. Copyright (C) 1998 by the American Society for Surgery of the Hand.