Abstract
Restoration of normal anatomy following a distal radial fracture is an important factor in determining functional recovery. However, current methods of assessing dorsal tilt and displacement require ‘true’ lateral radiographs, and important reference points are often obscured by metalwork.
Aims: to investigate if an easily identifiable and predictable relationship exists in the normal wrist between the distal radius and lunate; and if so,to compare fractured wrists (pre and postoperatively)using conventional and new assessment methods.
22 patients with displaced distal radial fractures treated by ORIF, were included. Patients had pre and postoperative radiographs taken of the injured and uninjured wrists. From lateral radiographs, measurements were performed using the PACS system. A line was superimposed upon the dorsal radial cortex 2cm proximal to the wrist passing distally. The following measurements were performed: lunate height, distance from the ‘line’ to the superior and inferior poles of the lunate, and conventional measurements of dorsal tilt and angulation.
Uninjured wrist: Most noticeably the dorsal radial line always passed superior to the lunate, mean distance of 3.27mm (1.75-6.6mm). As a ratio, the distance from the line to the superior pole of the lunate divided by the distance to the inferior pole (‘lunate ratio’) had a mean of 0.16 (0.11-0.19).
Fractured wrist, PreORIF: Using conventional methods, the mean fracture displacement was 2.64mm (0-5.1mm) and the mean dorsal tilt was 23.3 degrees(4 degrees volar tilt to 43 degrees dorsal tilt). Using the dorsal reference ‘line’, in all cases the lunate was either above or transected by the line; mean lunate ratio of 1.61 (0.54-8.05). The mean height of the lunate projecting dorsal to the line was 9.5mm (6.1-16.1mm).
Fractured wrist, PostORIF: Apart from one radiograph, the ‘line’ passed superior to the lunate; mean distance of 2.64mm (0-3.9mm), with a mean lunate ratio of 1.13 (0.61-2.74). These measurements correlated well with measurements of dorsal tilt and displacement.
Our study suggests that there is a strong relationship between the distal radius and the lunate that could be used to assess fracture displacement and quality of reduction. Its main advantages are simplicity and ease of use despite the presence of metalwork.
Correspondence should be addressed to Mr Carlos Wigderowitz, Senior Lecturer, University Department of Orthopaedic and Trauma Surgery, Ninewells Hospital and Medical School, Dundee DD1 9SY.
