KS44: CAS TKA – OPTIMISING COMPONENT ALIGNMENT IN KNEE ARTHROPLASTY USING CI NAVIGATION: A PROSPECTIVE RANDOMISED CONTROLLED STUDY

Abstract

Malalignment of knee arthroplasty components can lead to abnormal wear, premature loosening and patellofemoral problems. Computer assisted surgery has been developed to improve surgeons ability to achieve correct alignment and thereby improve outcomes. This project compares the accuracy of computer assisted total knee arthroplasty with a conventional jig-assisted technique.

A total of 150 patients were recruited. Selection criteria included patients presenting with degenerative or inflammatory joint disease who were candidates for total knee arthroplasty. Patients having revision procedures were excluded as were patients who previously had a corrective osteotomy. Ethics approval was obtained and patients consented for the study. Patients were randomly allocated to either the computer navigated or jig alignment groups via the sealed envelope system. Demographic patient data and intraoperative data were collected. Quality of life and function assessments made using the WOMAC and Knee Society Scores. The component position was assessed using the Perth CT protocol.

One hundred and fifty patients were recruited from Dec 2005 to July 2007. Five patients were excluded due to machine malfunction and two others were excluded due to insufficient data collected leaving 143 patients for the study. There was no difference in blood loss, post operative hemoglobin or patient length of hospital stay. There was no difference in the Knee Society knee or function scores at 12 weeks or the knee flexion range either at discharge or at 3 months follow up. There was a significant correlation in duration of surgery (p< 0.05) with the navigated cases taking an average 23 minutes longer. Both the conventional jig alignment and computer navigated techniques produced accurate results in all CT measurements except for the tibial slope where the navigated group (4.8+/−1.6) was closer to the elected posterior slope of 3.5+/− 1.5 than the jig system (6.4+/−2). Statistically significant differences in favour of the navigated group were also found for both femoral component rotation and tibial coronal alignment but the outliers beyond the accepted ideal alignment of 0+/−3 degrees for each parameter were minimal and equivalent for the two groups.

Computer navigation in knee replacement surgery is gaining popularity to improve component alignment and consequently the outcome of total knee arthroplasty. This study has shown only marginal benefits in alignment of the navigated group but this needs to be considered against the increased surgical time despite familiarity with the hardware.