Variability of the metaphyseal-diaphyseal angle in tibia vara: a comparison of two methods.

Although Levine and Drennan described the metaphyseal-diaphyseal angle (MDA) in tibia vara using the lateral border of the tibial cortex, there is a lack of uniformity in the literature. The authors measured the MDA using both the lateral border and the center of the tibial shaft in 132 knees (66 patients) with bowleg deformity and examined whether there is a significant difference between these two measurements. At angles < or =11 degrees there was significant variance between the two methods. At angles >11 degrees, there was excellent correlation between the two methods and no statistical difference between the two methods. The authors conclude that either method of defining the longitudinal axis is acceptable to measure the MDA for the diagnosis and monitoring of tibia vara.