THE LEARNING CURVE WITH COMPUTER ASSISTED TOTAL KNEE ARTHROPLASTY: A NOVICE COMPARED TO AN EXPERIENCED NAVIGATOR

Abstract

Computer assisted total knee arthroplasty (TKA) is still a relatively novel technique. Surgeons wishing to adopt any new practice undergo a learning curve. The learning curve experienced with navigated TKA, its duration and cost in terms of complications, has not been well defined in the literature. Therefore we set out to analyse the learning curve of a newly appointed consultant with no previous experience of navigated TKA by using a surgeon who has completed over 1000 TKAs in over 10 years of experience with this technique as a baseline.

The study used the inexperienced surgeon’s first ever fifty navigated TKAs and the experienced surgeon’s most recent fifty TKAs over the same period in the same theatre using the same CT free navigation system (Orthopilot^®) and prosthesis. Operative time, bone cuts and limb alignment before and after prosthesis implantation were recorded, along with the navigation specific difficulties and complications encountered by the inexperienced surgeon.

There was no statistical difference in the accuracy of postoperative limb alignment in either the coronal (p = 0.33) or sagital (p = 0.35) planes between the novice and experienced surgeon. There was also no difference in the executed bone cut angles (tibial p = 0.79, femoral p = 0.92). The operating time showed a difference between the two surgeons with the novice having a median of 80 mins (inter-quartile range of 20 mins) and the experienced surgeon had a median of 70 mins (inter-quartile range of 20 mins), p = 0.001. However there was a statistically significant reduction in operating time between the inexperienced surgeon’s first twenty and last twenty TKAs (p = 0.001). Comparison of the last 20 TKAs for each surgeon showed no difference in the operative time (medians of 70 mins and 75 mins respectively, p = 0.945). The navigation specific difficulties and complications recorded for the novice navigator were all related to the trackers: one loosening, one tibial tracker placed too proximally, one superficial infection in a tibial tracker wound and one incompletely engaged pin-tracker coupling which brought about the only conversion to manual TKA in this series.

We conclude that in terms of execution and outcome, a beginner using computer assisted TKA can match the results of an experienced navigator from the outset. The only parameter assessed that underwent a clear learning curve was the operative time, which took approximately 20 procedures to approach the same as the experienced surgeon.