CT MEASUREMENT OF TORSION OF THE LOWER-EX TREMITIES

The precise evaluation of post-traumatic deformities is indispensable when planning a corrective osteotomy. Torsional angles of the lower ex tremities of 186 patients were measured using CT. The mean age of the studied population was 34 years (18-80). It consisted of 131 men and 5 5 women. All patients had sustained a fracture of at least one of the leg's bony segments. The normal femoral (n = 293) inward torsion measu red 23.47-degrees +/- 17.16-degrees (xBAR +/- 2 SD). Normal tibia (n = 263) outward torsion was 34.03-degrees +/- 17.22-degrees. The intrain dividual torsional differences were not normally distributed. Normal f emoral (n = 103) intraindividual torsional difference measured 11-degr ees (95% percentile) and 15-degrees (99% percentile), with a median of 4-degrees. The tibiae (n = 76) showed a normal intraindividual torsio nal difference of 12-degrees (95% percentile) and 15-degrees (99% perc entile). Right tibiae showed a statistically significant greater outwa rd rotation when compared to their left counterpart (P < 0.001). No co rrelation to sex could be established. Preoperative planning of a corr ective osteotomy should include the geometric evaluation of all four b ony segments of the leg. Intraindividual torsional differences must be considered. A corrective osteotomy appears to be unnecessary with a t orsional difference smaller than 15-degrees in the femora and smaller than 15-degrees in the tibiae.