The retrospective multicenter study of 1,570 primary total knee arthroplasties (TKAs) by Kazarian et al. in the October 2, 2019 issue of JBJS focused on evaluating the impact of surgeon volume and training status on implant alignment. But the most surprising (and concerning) finding was that even among high-volume attendings—the best-performing of the three surgeon cohorts studied—the proportion of TKA alignment “outliers” was still high.
The authors radiographically measured 3 postoperative TKA alignment parameters: medial distal femoral angle (DFA), medial proximal tibial angle (PTA), and posterior tibial slope angle (PSA). Using established thresholds for “outliers” and “far outliers” for those 3 measurements, the authors compared the radiographic findings among surgeries performed by high-volume attendings (≥50 TKAs/year), low-volume attendings (<50 TKAs/year), and trainees (supervised residents or fellows).
As has been shown in similar studies of total hip arthroplasty (THA), the group of high-volume attendings outperformed the low-volume attendings and the trainee group on nearly all measurements assessed in this study. Interestingly, in terms of TKA alignment, the low-volume attending group and the trainee group performed similarly.
Kazarian et al. express concern that “even the most accurate cohort in our study, [the high-volume attendings], placed only 69.0% of knees in optimal alignment for all 3 measurements.” While the authors admit that implant alignment is not a perfect proxy for clinical outcomes, they argue that “gross alignment outliers are likely to have an impact on knee function, kinematics, and wear characteristics.” Citing literature suggesting that the use of robotic-arm assistance may improve TKA alignment, the authors surmise that employing such technology to assist low-volume surgeons or trainees might optimize alignment and improve outcomes, despite the added up-front cost of the technology.
