Background: Proponents of navigated knee arthroplasty stress its potential to increase the precision of component placement. We conducted a systematic review and meta-analysis to substantiate the validity and relevance of this contention.
Methods: We searched major medical and publishers' databases for randomized trials and any other studies comparing navigated with conventional knee arthroplasty. Major periodicals were searched manually. We made no restrictions for types of studies or language. Methodological features were rated independently by two reviewers. After testing for publication bias and heterogeneity was done, the data were aggregated by random-effects modeling. We estimated the weighted mean differences of mechanical limb axes and functional scales and the risk ratios of deviations from the straight axis with 95% confidence intervals.
Results: We included thirty-three studies (eleven randomized trials) of varying methodological quality involving 3423 patients with a mean age (and standard deviation) of 67.3 +/- 4.1 years (62.6% were women, and 83.7% had primary osteoarthritis). The mean preoperative deviation from the mechanical axis was 2.3 degrees +/- 5.1 degrees. There was no evidence of publication bias, but there was strong statistical heterogeneity. The alignment of the mechanical axes did not differ between the navigated and conventional surgery group (weighted mean difference, 0.2 degrees; 95% confidence interval, -0.2 degrees to 0.5 degrees). Patients managed with navigated surgery had a lower risk of malalignment at critical thresholds of >3 degrees (risk ratio, 0.79; 95% confidence interval, 0.71 to 0.87) and >2 degrees (risk ratio, 0.76; 95% confidence interval, 0.71 to 0.82). No conclusive inferences could be drawn on functional outcomes or complication rates. Navigation lengthened the mean duration of surgery by 23%.
Conclusions: Navigated knee replacement provides few advantages over conventional surgery on the basis of radiographic end points. Its clinical benefits are unclear and remain to be defined on a larger scale.