Radiological Assessment of Component Position and Limb Alignment in Coronal Plane after Total Knee Replacement with Image-free Navigation System

ABSTRACT

PURPOSE: We compared radiological measurements of component position and limb alignment in the total knee replacement(TKR) using image-free navigation system with those of conventional jig-based TKR. MATERIALS AND METHODS: TKR was performed in 52 knees(Group A) using image-free navigation system(Version 3.0, Stryker orthopedics, Kalamazoo, Michigan) and we compared them with same number of conventional jig-based TKR(Group B) in 43 patients from Mar. 2005 to Feb. 2006 in regard to coronal alignment of femoral(alpha) and tibial(beta) component, and mechanical femorotibial angle(mFTA;omega) on postoperative radiolographs. The differences in measure- ments of each group based on optimum angle and acceptable range(optimum angle+/-2 degrees) were used independent T-test and Pearson chi-square test respectively. The level of significance is less than 0.05 point. RESULTS: Postoperative radiographs for component position revealed the mean alpha angle was 90.0+/-1.3 degrees in group A and 88.7+/-2.2 degrees in group B, mean beta angle was 90.3+/-1.5 degrees in group A and 89.3+/-2.2 degrees in group B. Group A also showed significant difference in coronal alignment(alpha and beta) of components(p=0.001 and p=0.02) based on acceptable range. Long-leg standing view for limb alignment revealed mean mFTA was 1.4+/-1.3 degrees in the group A and 2.9+/-2.0 degrees in the group B(p=0.00). CONCLUSION: Total knee replacement using image-free navigation system revealed better results in coronal alignment of components as well as restoration of limb alignment based on optimum angle and acceptable range.