No Increased Risk of Patella Related Revisions When Comparing Ultra-Congruent Versus Cruciate-Retaining Polyethylene Liners in Primary Total Knee Arthroplasties with an Unresurfaced Patella: An Australian Registry Study of 42,105 Knee Arthroplasties.

Background: Ultra-congruent (UC) polyethylene liners are designed to add additional anterior-posterior stability in primary total knee arthroplasties (TKAs), compensating for actual or potential posterior cruciate ligament incompetence, somewhat like a posterior stabilized knee. The literature supports patella resurfacing in primary posterior-stabilized-compared to cruciate-retaining (CR)-TKA due to higher revision rates with non-resurfaced patella. However, it is unclear if UC liners alter patella-related revisions. The aim of the study was to compare patella revision rates and survivorship of UC versus CR liners in primary TKA without patella resurfacing using two common prostheses in patients who had osteoarthritis.

Methods: This was a retrospective cohort analysis of data from the Australian Orthopaedic Association National Joint Replacement Registry. Patients who underwent primary TKA utilizing one of two common knee systems with cemented tibial fixation for osteoarthritis and did not have their patella resurfaced between January 1, 2007, and December 31, 2022, were included for analysis. A total of 42,105 primary TKA procedures were included (UC n = 18,989, CR n = 23,116). The risk of patella-related revision and survivorship for primary TKA procedures with UC compared to CR liners were analyzed.

Results: The cumulative revision at 14 years was 5.7% (95% CI [confidence interval] 4.7 to 6.9) and 5.4% (95% CI 4.8 to 6.1) for the CR and UC group, respectively, with no difference between groups (entire period: HR [hazard ratio] = 1.07 (95% CI 0.95 to 1.20), P = 0.256). When revision TKA for patella-related diagnoses was analyzed, there was no difference between the CR and UC groups (entire period: HR = 1.10 (95% CI 0.88 to 1.38), P = 0.406). The prosthesis-specific analyses did not produce any differences between the groups for all-cause or patella-related revisions.

Conclusion: The use of UC compared to CR liners in primary TKA without patella resurfacing was not associated with an increased rate of all-cause or patella-related revisions. Surgeons should make clinical decisions on the need for patella resurfacing based on other patient, surgical, and implant factors.