INTRODUCTION:
Kinematic alignment (KA) using patient-specific instrumentation (PSI) has been proposed as an alternative to mechanical alignment in total knee arthroplasty (TKA), but long-term comparative survivorship data remain limited. This study compared long-term revision risk following KA-PSI TKA
with other TKA using the same implant design.
METHODS:
We performed a registry-based cohort study using data from the Australian Orthopaedic Association National Joint Replacement Registry and the New Zealand Joint Registry. All primary cruciateretaining
(CR) Triathlon TKA performed for osteoarthritis between January 1, 2011 and December 31, 2013 were included with follow-up through December 31, 2024. KA-PSI TKA were compared with all other CR Triathlon TKA of the same implant design performed using conventional or computerassisted techniques. The primary outcome was cumulative percent revision (CPR), and hazard ratios (HR) were derived using Cox proportional hazards models adjusted for age and sex.
RESULTS:
A total of 20,142 TKA were included, of which 449 were KA-PSI. Mean follow-up was 11.3 years for the KA-PSI group and 10.8 years for the comparator group, with a maximum of 13.7 years. The 13-year CPR was 5.0% (95% CI 3.2–7.8) for KA-PSI TKA and 4.4% (95% CI 4.1–4.7) for comparator TKA, with no difference in revision risk (HR 1.06, 95% CI 0.68–1.65; P = 0.85). Revision indications were similar between groups. Patella maltracking was the most common aseptic indication for revision
in the KA-PSI group (15% of revisions), while rates of individual failure modes did not differ significantly between groups.
DISCUSSION AND CONCLUSION:
Kinematically aligned CR Triathlon TKA implanted using patient-specific instrumentation demonstrated survivorship equivalent to conventional and computer-assisted techniques at up to 13 years. These findings support the long-term durability of kinematic alignment without an increased revision risk. Physicians should remain aware of the potential for patella-related complications following KAPSI.
