Total Limb Rotation after Unilateral Total Knee Arthroplasty: Side-to-Side Discrepancy

Total limb rotation, an important anatomical feature of the lower limb, is defined as any rotation of the lower limb on its longitudinal axis. The aim of the present study was to evaluate the discrepancies of rotational profiles of total limb between nonoperated and operated limb following unilateral total knee arthroplasty. We conducted an analysis of the computed tomography (CT) data from 32 patients undergoing primary unilateral total knee arthroplasty. Using these CT scan, rotational profiles of total limb, such as femoral neck anteversion angle expressed as femoral torsion angle (FTA), tibial torsion angle (TTA), knee joint rotation angle (KJRA), and total limb rotation (TLR) were measured. There were significant discrepancies of FTA and KJRA between operated and nonoperated limb following unilateral total knee arthroplasty. The mean difference of operated and nonoperated side for FTA and KJRA were -6.51 ± 11.88 degrees (p = 0.0041) and -6.83 ± 5.04 degrees (p < 0.001), respectively. However, there were no significant discrepancies of TLR, TTA. These results are due to the compensation effect of KJRA. However, excessive external rotation of the femoral component beyond the compensation effect of prosthetic knee joint can lead to a total limb rotational discrepancy in patient undergoing unilateral total knee arthroplasty.