Variability in radiographic measurement of bowleg deformity in children.

The tibial metaphyseal-diaphyseal (MD) and tibial-femoral (TF) angles were measured on the radiographs of 33 knees in young children (aged 12-36 months) with bowleg deformity. Four observers of differing experience measured the films in a blinded fashion to determine the intraobserver and interobserver variability of these measurements. The clinical implications of these variabilities are described. Very little instruction and experience is necessary to make these measurements correctly and precisely. Measurement of the MD angle was superior to measurement of the TF angle. Contrary to published opinion, rotation can have a small but potentially significant effect on the measured MD angle.