Abstract
Introduction and Aims: Computer-assisted surgery may significantly improve the accuracy of total knee arthroplasty. The reproducibility of acquiring points that facilitate the computer generation of joint morphology which is fundamental for guiding surgery remains unclear. The aim of this study was to assess inter- and intra-operator reproducibility using a computer guidance system.
Method: Three surgeons were involved in this study, who under instruction from a proprietary computer system acquired points on a sawbone model of the knee that correlated with specific anatomic landmarks. This process was performed five times each and repeated on another identical model. The points acquired allowed the computer to generate a knee joint model that predicted size, orientation and alignment of the knee joint. Inter- and intra-operator comparisons of the size of the prostheses, the amount of resection, the rotation of the prostheses, and the relationship of the epicondylar to the posterior femoral condylar axis were made.
Results: This study was commenced one day after an eight-hour hands-on workshop describing the use of the computer guidance system. The computer system accurately recorded the acquisition of points on a sawbone model. There was little difference in the time taken by each surgeon to acquire the points. Although, all iterations of point acquisition were performed sequentially, there was no clear reduction in the time taken for the process of acquisition. Despite the repetitive use of identical sawbone models, all three surgeons demonstrated significant variation within their own and between each others’ acquisitions. This resulted in variations of prosthetic sizes, amounts of bone resection and rotation of implants. The consistency at which certain indices differed suggested a specific bias between surgeons that may reflect technique or interpretation of anatomic landmarks, e.g. relationship between the epicondylar and posterior condylar axes.
Conclusion: An important reason for the variation may be the difference in interpretation of the location of anatomic landmarks. This may have a significant impact on the generation of computer model for guiding subsequent surgery. Clear definitions of landmarks and a robust education program is required if computer assisted surgery is to be accurate and meaningful.
These abstracts were prepared by Editorial Secretary, George Sikorski. Correspondence should be addressed to Australian Orthopaedic Association, Ground Floor, The William Bland Centre, 229 Macquarie Street, Sydney, NSW 2000, Australia.
None of the authors is receiving any financial benefit or support from any source.
