THE EFFECT OF BEARING SURFACE ON CEMENTLESS AND HYBRID TOTAL HIP ARTHROPLASTY SURVIVAL: AN UPDATED ANALYSIS OF CONTEMPORARY BEARING DATA FROM THE NATIONAL JOINT REGISTRY AND HOSPITAL EPISODE STATISTICS

The aim of this project was to analyse the effect of contemporary THR bearings on THA survival. This is an updated report of our previous analysis with longer follow up and now includes antioxidant-stabilised polyethylene bearings. We combined the NJR dataset with polyethylene manufacturing properties to sub-divide polyethylene into conventional (PE) and highly crosslinked (XLPE). Only THAs with a cementless acetabular component were included. The Hospital Episode Statistics (HES) dataset was used to link ipsilateral surgical procedures for the treatment of peri-prosthetic hip fractures. Reoperation for peri-prosthetic fracture was defined as revision as registered by the NJR or fixation as captured by the HES dataset. Cause-specific and overall reasons for revisions were analysed using Kaplan-Meier and multi-variate Cox proportional hazard regression survival analyses. A total of 696,013 THAs and 17,468 reoperations were included in this analysis. Regression analysis with metal on XLPE as the reference bearing adjusted for age, sex, stem fixation and head size revealed that the lowest risk of revision for any reason was in Ceramicised Metal on XLPE (HR= 0.77, 95% CI = 0.69 – 0.86) followed by Ceramic on Antioxidant XLPE (HR 0.78, 95%CI = 0.68 – 0.88), Ceramic on XLPE (HR= 0.86, 95%CI = 0.82 – 0.91), Ceramic on Ceramic (HR 0.95, 95%CI= 0.90 – 1.0) and Metal on Antioxidant XLPE (HR 1.02, 95%CI= 1.05 – 1.14). Age under 55 at primary, male sex, cementless stem fixation and head size of 28mm were associated with a higher risk of revision. In this updated report with longer follow up, XLPE-based bearings were associated with the lowest risk of revision. The lowest risk of revision for aseptic loosening and revision for all reasons was in CMoXLPE THAs.