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.