Intraoperative assessment of femoral component rotational alignment in total knee arthroplasty

Poor clinical results following total knee arthroplasty like flexion gap instability or anterior knee pain may be related to femoral component rotational malalignment. The transepicondylar axis has been recommended as a landmark to consistently recreate a balanced flexion gap. However, the reproducibility to identify the transepicondylar axis intraoperatively is low. In this feasibility study we wanted to find out whether fluoroscopy-based CT scans obtained by a motorized mobile C-arm (Iso C 3D) may be useful to asses the transepicondylar axis intraoperatively. Following the femoral resections the Iso C 3D was used intraoperatively in ten knees with mild to severe deformities. On multiplanar reconstructions of the distal femur the clinical epicondylar axis as well as the angle to the posterior cut (condylar twist angle) could be easily measured. The scanning time was 40 s and the extra time needed for the whole setup about five to ten minutes. The Iso C 3D was helpful to intraoperatively identify the transepicondylar axis and the condylar twist angle, especially in cases with severe deformity or dysplasia when standard landmarks are difficult to determine.