Total knee arthroplasty provides durable results and is reliable at relieving pain and improving function in patients with arthritis of the knee. The goal during surgery is to achieve a well-aligned total knee prosthesis with ligament-balancing to minimize wear and implant stress. Restoration of alignment close to the mechanical axis has been one of the main tenets of knee replacement surgery over the past four decades.

In their study, de Steiger et al. present interesting and novel data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). They analyzed data that had been prospectively collected from 2003 through 2012 and compared the revision rates and reasons for revision surgery in a cohort of patients who had undergone primary total knee arthroplasty with or without computer navigation. The principal finding of this study was that while computer-assisted surgery did not significantly reduce the overall revision rate in the entire study population, it did reduce the overall revision rate and the risk of revision for aseptic loosening in patients younger than sixty-five years of age. The authors postulated that the lower rate of failures in these younger patients over this ten-year observational period may have been due to more accurate implant position resulting from the use of computer navigation.

This study has several strengths and weaknesses and, therefore, one must critically evaluate the data and methodology and determine which conclusions are supported by the study results. First, the data represent the vast, aggregated contributions by all of the practicing orthopaedic surgeons in Australia. Because individual surgeons vary with regard to their practice pattern, clinical experience, and surgical volume, the aggregated data represent and are applicable to all surgeons. Second, the AOANJRR is well designed and managed with various checks and balances ensuring high surgeon compliance and the capture of reoperations and revisions. Thus, the reported revision and reoperation rates are accurate, and the risk of sampling bias is minimized. Finally, the registry includes detailed data such as implant design, mode of fixation, and surgeon volume. Consequently, these data can be effectively used for postmarket surveillance of hip and knee implants and help identify trends and early failures as in the case of metal-on-metal hip replacements.