[CT determination of leg length and torsion in children and adolescents].

Because of different projections and axis constructions, the length and torsion of the lower extremities are sensitive to the measuring method. To judge pathological deformities in children or adolescents it is necessary to know the reference values. In this study, 78 children and adolescents 2-18 years old were included who had a femoral or tibial shaft fracture. Torsion and length were determined by computed tomography at least 3 months after internal fixation according the Ulm method. Only healthy bones were considered for this study. The mean internal torsion of the femur decreased during the growth period from 34.2 degrees +/- 10.3 degrees (x +/- SD) to 19.3 degrees +/- 9.5 degrees. There was only a weak correlation between the age and torsion of the femur. The mean external torsion of the tibia was 32.3 +/- 10 degrees. The 95th percentiles of the intraindividual torsional differences were 14 degrees (x = 4.1 degrees) of the femur (n = 30) and 12 degrees (x = 4.7 degrees) of the tibia (n = 48). The median femoral and tibial intraindividual length differences were 2 mm. The corresponding 95th percentiles were 10 and 9 mm. The aim of the study was to determine the age-dependent torsion and length and their respective differences with a standardized CT method. The range of the normal values was much greater than published in the literature.