Accuracy of Limb Alignment in Total Knee Arthroplasty using Image-Free Navigation System: Comparison with Conventional Total Knee Arthroplasty

ABSTRACT

PURPOSE: We analyzed the comparative results of limb alignment after total knee arthroplasty using conventional method and image-free navigation system. MATERIALS AND METHODS: Total knee arthroplasties were performed in sixty-four patients(74 knees) with conventional method(37 cases)(Group A) and Orthopilot 4.0 image-free navigation system(37 cases)(Group B). We measured the femoro-tibial angle, femoral and tibial component angle in coronal and sagittal plane using the weight bearing whole leg radiograph taken 1-month postoperatively. RESULTS: Mechanical femoro-tibial angle was 1.4 degrees of varus in conventional group (Group A) and 0.8 degrees of varus in the navigation group (Group B) on average. Femoral and tibial component angle in the coronal plane was mean 1.8 degrees of varus and 0.7 degrees of varus in group A, 0.3 degrees of valgus and 0.5 degrees of varus in group B on average. Average femoral and tibial component angle in sagittal plane was 0.3 degrees of flexion and 0.8 degrees of anterior tilt in group A, 0.7 degrees of flexion and 1.7 degrees of anterior tilt in group B. There were no statistically significant differences between two groups in the femoro-tibial angle, femoral and tibial component angle in coronal and sagittal plane. But the ranges of deviation from desired angle were smaller in Group B than Group A. Statistically significant different results of the limb alignment (femoro-tibial angle and femoral component angle in coronal plane) were observed in 5 cases with severely bowed femoral shaft in group B (average femoro-tibial angle 0.9 degrees and femoral component angle in coronal plane 0.9 degrees varus) than group A (average femoro-tibial angle 3.5 degrees and femoral component angle in coronal plane 3.9 degrees varus). CONCLUSION: Accuracy of limb alignment in total knee arthroplasty using navigation system was not statistically significant difference than using the conventional method, but had better results in the deviation of mechanical femoro-tibial angle and femoral component angle in coronal plane than the conventional method, especially in severely bowed femoral shaft.