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

Abstract

Background and purpose 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).

Method 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.

Results 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.

Interpretation 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.

Study concept and design: VM, MCSI, and RSN. Extraction of data and preparation of raw data: MCSI. Statistical analysis: MCSI. Interpretation of data: VM, MCSI, RSN, DS, and EWP. Drafting of the text: VM and MCSI. Drafting of th tables: MCSI. Critical revision of the manuscript for important intellectual content: VM, MCSI, RSN, DS, and EWP.

We thank all Kaiser Permanente orthopedic surgeons and the staff of the Department of Surgical Outcomes and Analysis who have contributed to the success of the National Total Joint Replacement Registry.

No competing interests declared.