Abstract
BACKGROUND: In congenital posteromedial bowing of the tibia, the remodeling of triplanar (medial, posterior and oblique) deformities, the resolution of tibial shortening and their correlation with each other have not been studied extensively. Additionally, the age at which tibial shortening at maturity can be accurately predicted under these conditions is not known. This study aimed to evaluate the natural history of tri-planar deformity remodeling, the resolution of tibial shortening and the difference between tibial shortening predicted by the multiplier method at first presentation and subsequent follow-up. METHODS: All consecutive children with congenital posteromedial bowing of the tibia (with a minimum of 2 years of follow-up) were prospectively evaluated. The severity of the bow was measured with diaphyseal and interphyseal (antero-posterior, lateral) angles. The percentage shortening (length of affected/normal side × 100) of the tibia was estimated at presentation and every year. The oblique plane deformity was calculated as per the trigonometric model. The multiplier method was used at presentation and at every follow-up to estimate tibial shortening at maturity, and the significant differences between the values were analyzed. Differences in the rates of deformity remodeling and the resolution of tibial shortening were compared by the Wilcoxon test. Spearman correlation was performed to assess the correlation between the degree of deformity remodeling and the resolution of tibial shortening. RESULTS: Fifty-one children (21 boys, 30 girls) with a median duration of follow-up of 48 months were studied. The rate of remodeling of the posterior diaphyseal bow was greater than that of the median diaphyseal and oblique diaphyseal bows. The median rate of remodeling of the diaphyseal bows and interphyseal angles in the first year of life halved its value in subsequent years, and minimal remodeling was noted after 4-6 years of age. A total of 20% of tibial shortening at presentation resolved to 13% shortening at 6 years of age. There was no significant difference in tibial shortening estimated at maturity using the multiplier method after two years of age. CONCLUSION: Remodeling of the deformity and resolution of shortening provide better insight into deformity correction and planning for limb length equalization.