Monoblock all-polyethylene tibial components have a lower risk of early revision than metal-backed modular components

With younger patients seeking reconstructions and the activity-based demands placed on the arthroplasty construct, consideration of the role that implant characteristics play in arthroplasty longevity is warranted. We therefore evaluated the risk of early revision for a monoblock all-polyethylene tibial component compared to a metal-backed modular tibial construct with the same articular geometry in a sample of total knee arthroplasties (TKAs). We evaluated risk of revision in younger patients (< 65 years old) and in older patients (≥ 65 years old).

Fixed primary TKAs with implants from a single manufacturer, performed between April 2001 and December 2010, were analyzed retrospectively. Patient characteristics, surgeon, hospital, procedure, and implant characteristics were compared according to tibial component type (monoblock all-polyethylene vs. metal-backed modular). All-cause revisions and aseptic revisions were evaluated. We used descriptive statistics and Cox regression models.

27,657 TKAs were identified, 2,306 (8%) with monoblock and 25,351 (92%) with modular components. In adjusted models, the risk of early all-cause revision (hazard ratio (HR) = 0.5, 95% confidence interval (CI): 0.3-0.8) and aseptic revision (HR = 0.6, CI: 0.3-1.2) was lower for the monoblock cohort than for the modular cohort. In older patients, the early risk of all-cause revision was 0.6 (CI: 0.4-1.0) for the monoblock cohort compared to the modular cohort. In younger patients, the adjusted risk of all-cause revision (HR = 0.3, CI: 0.1-0.7) and of aseptic revision (HR = 0.3, CI: 0.1-0.7) were lower for the monoblock cohort than for the modular cohort.

Overall, monoblock tibial constructs had a 49% lower early risk of all-cause revision and a 41% lower risk of aseptic revision than modular constructs. In younger patients with monoblock components, the early risk of revision for any cause was even lower.