A more accurate method of measurement of angulation after fractures of the tibia

Accurate measurement of the alignment of the tibia is important both clinically and in research. The conventional method of measuring the angle of malunion after a fracture of the shaft of the tibia is potentially inaccurate because the mechanical axis of the normal bone may not pass down the centre of the medullary canal. An alternative method is described in which a radiograph of the opposite tibia is used as a template. A sample of 56 sets of standard radiographs of healed fractures of the shaft of the tibia was evaluated. The 95% limits of agreement between this and the conventional method were wide, being -6.2 degrees to +5.5 degrees for coronal angulation and -6.7 degrees to +8.1 degrees for sagittal angulation. These results suggest that the conventional method is inaccurate. The new method has good inter- and intraobserver reliability.