A Novel Approach to Lower-limb Axial Alignment Analysis: A CT Study

To analyze the torsion of the lower extremities in a healthy cohort and to determine the contribution of different segments of the femur and tibia to the torsion of both bones. METHODS: In this cross-sectional study, 32 patients with nonjoint or bone-related symptoms were analyzed by CT angiography. Lower-limb torsion, femoral torsion, proximal femoral torsion, femoral shaft torsion, distal femoral torsion, tibial torsion, proximal tibial torsion, and distal tibial torsion were measured. RESULTS: The median total limb torsion was 25° external torsion, with the median femoral torsion being −9° and the median tibial torsion 30°. Both femoral metaphyses had internal torsion, with the internal torsion of the proximal metaphysis being approximately three times greater than that of the distal femoral metaphysis. The shaft was found to compensate with an external torsion of approximately two-thirds of the internal torsion of both femoral metaphyses. The proximal metaphysis of the tibia accounted for approximately one-third of the external torsion, with the segment from the distal to the tibial tubercle accounting for the remaining two-thirds of the tibial torsion. CONCLUSIONS: The diaphysis and distal metaphysis are the major contributors to external torsion of the tibia, whereas the proximal metaphysis is the major contributor to the internal torsion of the femur.