A randomized controlled trial to compare component placement in navigated total knee arthroplasty using original and streamlined registration processes.

BACKGROUND: This randomized controlled trial validated a redesigned version of navigated total knee arthroplasty software with a streamlined registration (Smart) against the previous version (Classic). The objectives were to determine if Smart software had the same accuracy of component positioning and whether registration and operative time were reduced. METHODS: A total of 220 patients were recruited and had a navigated total knee arthroplasty performed. With the exception of the software, all patients had the same perioperative care. At 6-week follow-up with an independent arthroplasty service, all patients had a computerized tomography scan. This was assessed by an independent radiologist to measure the mechanical alignment of the components. RESULTS: The mean postoperative mechanical femorotibial angles were equivalent between groups (mean difference -0.2°, 95% confidence interval -0.7° to 0.3°, P = .407). Component positions were similar in both groups. Mean registration time was significantly shorter for the Smart group (2 minutes 30 seconds ± 54 seconds) than the Classic group (3 minutes 23 seconds ± 39 seconds), P < .001. The mean operative time was 72 ± 12 minutes in both groups (P = .855). At 6-week follow-up, both groups had similar clinical outcomes with 96.5% of patients being satisfied or very satisfied. CONCLUSIONS: The study verified that a reduced registration time did not alter the accuracy of component placement. However, despite a shorter registration time, the overall surgical time was not reduced.

Computer navigated total knee arthroplasty: the learning curve.

The learning curve for computer navigated total knee arthroplasty (TKA) is not well defined. We collected data prospectively on a consultant surgeon's first 50 navigated TKAs. Over the same period, matching data was taken from 50 consecutive cases performed by an expert who has performed over 1000 navigated TKAs. From the first case, the novice navigator was able to achieve the same standard as the expert in terms of post-implant mechanical alignment in the coronal and sagittal planes. Equally, at 6 weeks and one year post-surgery there was no significant difference in the mean Oxford score, mechanical axis and range of movement for the two groups of patients. Operative time was significantly longer for the novice surgeon in the first 20 cases (92 versus 73 min, p < 0.001), but by the final 20 cases there was no difference (72 versus 74 min, p = 0.944). This study shows that the learning curve for navigated TKA is approximately 20 cases and that a beginner can reproduce the results of an expert from the outset.