Assessing distal radius malrotation following fracture using computed tomography.

Hypothesis: When the distal fracture fragment in distal radius fractures displaces, it commonly rotates as well as shortens and angulates.

Aim: The aim of this study was to assess the frequency and magnitude of malrotation of the distal fracture fragment using computed tomography (CT).

Methods: A retrospective radiological assessment of 85 CT scans of the distal radius, 35 following fracture and 50 normal radii, was carried out. We developed and applied a simple method for measuring rotation of the distal radius relative to the diaphysis using routine CT scans of the wrist. A Mann-Whitney analysis was used to identify differences in radial rotation between fractures and controls. Intra- and inter-observer reliability were analyzed using intra-class correlation coefficients (ICCs) and Bland-Altman plots.

Results: The articular surface of the distal radius is normally rotated in the long axis of the forearm relative to the diaphysis, either into pronation or into supination. The median radial rotation angle of controls was 1° pronation (range -15° to 4°) compared to 3° pronation (range -24° to 31°) in the fracture group. The absolute rotation angle was significantly greater in the fracture group (median 10°, range 0-31° vs. 3°, range 0-15°; < 0.001) and outside the "normal range" of controls in 26 cases indicating that 75% had rotated appreciably following injury. Intra- and inter-observer reliability of measurements were good with ICCs of 0.99 and 0.98, respectively.

Conclusions: Malrotation of the distal radius appears common following distal radius fracture. Malrotation of the distal fracture fragment has been shown to affect distal radio-ulnar joint function. Despite this, rotational deformity is rarely addressed in clinical practice as it is difficult to appreciate on simple radiographs. The simplified method described here is easy to use in routine clinical practice and also appears reliable. Measuring radial rotation may be an important consideration when planning both primary treatment and corrective osteotomy for patients with distal radial malunion.