Clinical Study On The Effect Of Femoral Component Rotation On Patellar Tracking In Total Knee Arthroplasty

ObjectiveThe purpose of this study was:1. To compare and analyze the anatomical features of posterior condylar angle (PCA) of Chinese KOA patients'knees, and study the effect of preoperative coronal deformity on PCA.2. To study the relationship between PCA and patellar tilt angle (PTA) postoperatively, and analyze the effect of the rotation alignment of femoral component using post condylar axis on patellar tracking in total knee arthroplasty (TKA).To offer clinical data of the Chinese knees for the improvement of surgical techniques in TKA and to reduce postoperative complications of patellofemoral joint.MethodsWe chose 34 KOA patients (52knees) as subjects, who were performed routine primary TKA with unreplaced patella using PFC systems (DePuy, Warsaw, Ind) and neither lateral nor medial retinacular release was performed.These patients were grouped by gender and coronal deformity of knee preoperatively and by gender and rotation of femoral component postoperatively.We obtained computed tomography scans (CT) of the patients before and after they underwent TKA and measured the posterior condylar angle on the femoral side. We obtained postoperative Merchant patella view and measured patellar tilt angle (PTA).CHISS2005 software was used for statistical analysis, and measurement data were expressed in the form of mean value±tandard deviations.Results 4 knees were excluded because of unidentification of the epicondylar axis.Mean PCA was 2.92°±1.66°. In the valgus deformity group mean PCA was 4.64°±0.90°and 2.57°±1.52°in varus deformity group and 2.40°±1.65°in no coronal deformity group. The result was statistically significant between valgus deformity group and the others.Mean PTA was 5.46°±3.90°. In the internal rotation group mean PTA was 7.43°±3.47°and 3.14°±3.04°in external rotation group. The result was statistically significant. There was a linear relationship between the PCA and PTA.ConclusionsThe PCA was significantly greater in valgus knees than in other osteoarthritic knees. The posterior condyles are potentially unreliable references for femoral component rotation in some knees.Orientation of the femoral component affects ostoperative patellar tracking. Femoral component external rotation to the epicondylar axis had a better patellofemoral joint interaction than internal rotation and therefore produces minimized anterior knee complications after TKA.