Computer Navigation Versus Conventional Total Knee Replacement

Spencer JM et al.
The Journal of Bone and Joint Surgery (Br).2007; 89-B: 477-480

Computer navigation for total knee replacement (TKR) is a relatively new technique, allowing accurate positioning of the components relative to the mechanical axis of the limb. In 2004, a cohort of 71 patients undergoing TKR, were prospectively and randomly allocated to either undergo a computer-navigated (CN) or conventional TKR. A significantly improved alignment in the CN TKR group was reported.

This paper presents the two year follow up results for these patients. The patients were reviewed by physiotherapists independent of the operating surgeon. Each patient was examined pre-operatively and thereafter at intervals for 2 years. Patients were assessed using the Knee Society score (KSS), Western Ontario and McMaster (WOMAC) Universities osteoarthritis index, the Short Form 36 (SF-36) health survey, Oxford knee score and the specific Bartlett Patellar score. These looked at the patient’s pain, range of physical functioning, activities of daily living, general health, vitality, social functioning, emotional and mental health. The patients also rated their replacement by a satisfaction questionnaire.

A total of 60 patients from the study (30 CN TKRs and 30 conventional TKRs) completed the follow-up. It was found that after two years there was no significant difference in the knee function and the incidence of anterior knee pain between a patient receiving a CN or a conventional TKR. The satisfaction rates for both groups were 86.7% (26) of the CN and 83.3% (25) of the conventional group, satisfied to some extent with the result of their joint replacement.

Improved TKR alignment can reduce the process of abnormal wear. Power analysis was conducted for the original study this was not done for these functional variables, meaning that these results may need further examination. TKR is a very successful operation with a high level of patient satisfaction and functional improvement, it may therefore, be difficult for CN to show a significant improvement in these variables in the short term when all it does is provide better component alignment with similar short term clinical results to conventional surgery. Longer term results are needed to see if there is a lower rate of failure of CN patients from wear.

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