Comparison of patellar tracking according to different angles of external rotation of femoral component in varus knee of Asians

Abstract

Purpose: Racial difference in the femoral geometry may exist. Asian femurs may be more externally rotated. If anatomical differences in distal femur had existed between Caucasians and Asians, the group with 5° external rotation of the femoral component should have shown better results than the group with 3° external rotation of the femoral component have. Methods: 598 patients underwent total knee arthroplasty in our institution, among whom 83 patients (115 knees) who had postoperative computed tomography (CT) were studied retrospectively. Sixty-two knees were set in 5° of external rotation of femoral component relative to the posterior condylar axis (group A) while the others (53 knees) were set in 3° (group B). The femoral component rotation (FCR) was measured and compared using CT. The patellar tilting (PT) and the lateral patellar displacement (LPD) were measured to evaluate the patellar tracking using Merchant view. And postoperative clinical scores were compared. Results: The mean FCRs showed no significant difference between two groups ( p > 0.05). The mean PT and LPD showed no statistically significant difference either ( p > 0.05). There were no statistical differences in clinical scores. Conclusion: The difference in the patellar tracking between the two groups could not be demonstrated. There were no statistical differences in clinical scores either. We concluded there is no need to adhere to 5° external rotation.