The Radiographic Comparative Study of the Unicompartmental Knee Arthroplasty: Manual versus Navigation System

Abstract

Purpose : To compare the radiographic results of unicompartmental knee arthroplasty using a navigation system with those using a manual alignment system. Materials and Methods : The results of 50 cases (46 patients) of unicompartmental knee arthroplasty using a navigation system (24 patients, 25 cases) and using a manual alignment system (22 patients, 25 cases) were evaluated. Knee anteroposterior, lateral, and weight-bearing full-length lower extremity radiographs before and after the arthroplasty were used for the measurements. Results : The mean postoperative femorotibial alignment was 3.6 of valgus in the manual alignment group and 5.4 of valgus in the navigation group. The postoperative mechanical axis measured using Kennedy and White's method was located at zone 1 in 4 cases (16%), at zone 2 or C in 21 cases (84%) in the manual group, and at zone C for all cases in the navigation group (p=0.001). In the coronal axis of the femoral component, 11 cases (44%) were excellent, 7 cases (28%) were good and, 7 cases (28%) were poor in the manual alignment group. In the navigation group, 15 cases (60%) were excellent and 10 cases (40%) were good and there were no poor results (p＜0.05). In the coronal axis of the tibial component, 22 cases (88%) showed excellent results and 3 cases (12%) showed poor results in the manual alignment group. In the navigation group, all cases were showed excellent results (p＞0.05). In the sagittal axis of the tibial component, 9 cases (36%) showed poor results in manual group and there were no poor results in the navigation group (p＜0.05). Conclusion : Unicompartmental knee arthroplasty using navigation produced better results in restoring the alignment of the prosthesis and the mechanical axis of the lower extremity than that using manual alignment.