[Computer-assisted implantation of a total knee arthroplasty: a case-controlled study in comparison with classical instrumentation].

PURPOSE OF THE STUDY: The quality of total knee arthroplasty (TKA) implantation is an essential factor determining long-term outcome. Computer-assisted implantation could improve quality compared with conventional manual instrumentation.

MATERIAL AND METHODS: We studied the radiographic quality of TKA implantation in 100 patients with primary degenerative knee disease who underwent a computer-assisted procedure guided by an informatic navigation system without imagery (group A) or a conventional manual procedure (group B). The two groups were matched for age, sex, initial frontal mechanical tibiofemoral angle and severity of the degenerative lesions. Postoperative telemetry was used in accordance with the Knee Society guidelines to measure the frontal mechanical tibiofemoral angle and the frontal and sagittal tilt of the tibial and femoral components. The number of optimal implantations for the five measured criteria was chosen as the main study criterion. The two groups were compared using the chi-squared test with statistical significance set at 5% and power at 80%.

RESULTS: Globally, implantation of the prosthesis was considered to be optimal in 33 patients in group A and in 15 in group B (p<0.001). Mean angles were not different between the two groups, except for sagittal tilt of the femoral piece. The frontal mechanical tibiofemoral angle was considered optimal in 47 patients in group A and in 39 in group B (p<0.05). A significant improvement in the quality of the implantation was also found in group A for frontal tilt of the femoral piece (p=0.05), frontal tilt of the tibial piece (p<0.05) and sagittal tilt of the tibial piece (p<0.001). No particular peroperative difficulty or complication was related to the navigation system.

DISCUSSION AND CONCLUSION: The navigation system allowed a significant improvement in the quality of implantation of TKA compared with conventional instrumentation controlled by the surgeon's hand and eye. Only minimal changes in the operative technique are necessary and standard preoperative investigations remain unchanged. Long-term survival of prostheses implanted with this system could thus be improved compared with manually implanted TKA. The system used here does not involve preoperative imaging and allows a precision to the order of 1 degree for angles and 1 mm for lengths.