Displaced distal radial fractures in adults are commonplace. Acknowledging that satisfactory radiographic parameters typically will beget satisfactory functional outcomes, management of these fractures includes a reduction followed by either cast/splint immobilisation or internal fixation. While we can generally rely on internal fixation to maintain the reduction the same is not true of cast immobilisation. There are, however, limited data defining the fate of a fracture reduction in those treated in a cast and up to the time of radial union. Traditional practice is to recommend six weeks of immobilisation. Our goal was to detail the radiographic patterns of change in the radiographic parameters of radial inclination (RI), ulnar variance (UV) and radial tilt (RT) over the first twelve weeks in women fifty years old and older who had sustained a displaced distal radial fracture.

We examined serial standard PA and lateral distal radius radiographs of 647 women treated by closed reduction and casting for a displaced fracture of the distal radius. Measurements of RI, UV and RT from standardised radiographs were made immediately post-reduction as well as, as often as possible/feasible, at 1,2,3,6,9 and 12 weeks post fracture. All measurements were made by the senior author (accuracy range: 2 degrees for RI, 1 mm for UV and 4 degrees for RT, in 75% of cases). The primary outcome measure was the change in fracture position over time. Secondary outcomes included changes related to age group; known bone density; the relation to associated ulnar fractures; and independence of the variables of RI, UV and RT.

The mean immediate post-reduction values for RI, UV and RT were 21 degrees, 1.5 mm, and −6 degrees, respectively. These all changed in the first six weeks, and did not in the second six week period. The mean change in RI was 3 degrees, 60% of the change occurring in the first week post-reduction; only 0.3 degrees of change was noted beyond three weeks. The mean UV increased by 2.2 mm over the first 6 weeks, 23% in the first week post reduction. The mean RT change of 7.7 degrees was also gradual over the first 6 weeks, with no significant change afterwards. The RI changes identified were not influenced by patient age, while UV and RT changes were greater in older groups. Those fractures of the distal radius associated with a distal ulnar shaft or neck fracture did not lose radial inclination over the study period.

We have defined patterns of loss of reduction that commonly occur post reduction of a displaced distal radius fracture in women fifty years and older. Such patterns ought to guide our closed management of distal radial fractures, whether by altering the duration or method of casting. Women fifty years old and older, and physicians alike, must be advised that conventional casting post distal radial fracture reduction unreliably maintains fracture reduction.