The unstable Colles' fracture.

One hundred and twenty-one displaced Colles' fractures were assessed radiographically until union. An acute loss of position occurred during the first week of splintage, necessitating re-manipulation in six fractures. In the remaining 115 fractures whose position had been retained after one week, chronic instability led to a mean increase of 8.22 degrees dorsal angulation, a mean loss of 5.61 degrees radial angle, and 3.26 mm radial shortening. The extent to which the chronic collapse of radial angle and length occurred was determined solely by the initial deformity and was not related to either intraarticular involvement or the presence of radiographically visible comminution. However, the absence of radiographically visible comminution of the dorsal radius did confer stability against mal-union in dorsal angulation.