Failure modes of mechanically aligned versus kinematically aligned total knee arthroplasty

While mechanical alignment (MA) has long been considered the "gold standard" technique when performing total knee arthroplasty (TKA), kinematically aligned (KA) TKA has been gaining recent popularity. This technique aims to restore the pre-arthritic knee anatomy and alignment, with studies demonstrating excellent functional and biomechanical outcomes when compared to MA TKA. The primary aim of this study is to compare reasons for reoperation in MA versus KA primary TKA and understand if the reasons for re-operation differ between the two techniques.

This is a retrospective study including 267 patients who underwent a MA TKA from September 2017 to September 2021, compared to 359 patients who had a KA TKA from October 2021 to December 2024. All procedures were performed by a single arthroplasty-trained surgeon who switched his technique for TKAs in October 2021 from MA to KA. The primary outcome assessed was reoperation, with notes reviewed to assess the reason for reoperation.

While the MA cohort had a higher rate of reoperation (4.1%) compared to the KA cohort (2.2%), it was not significantly different (p = 0.172). Common reasons for reoperation included prosthetic joint infection, extensor mechanism disruption, peroneal nerve injury, and mechanical instability. There was no difference in rates of MUA between the MA and KA cohorts (4.1% versus 2.8%; p = 0.359).

In this study, we found no significant difference in reoperation rates between MA and KA primary TKAs. Prosthetic joint infection was a common cause of reoperation amongst both groups. More MA patients required reoperation for extensor mechanism dysfunction while KA patients experienced more mechanical instability.