Mortality following elective total hip replacement and hip resurfacing

Abstract

Background: Although hip replacement is a highly successful surgical treatment for symptomatic hip OA, the operation has inherent risks including death. Severe hip pain can be so debilitating that people balance their expectations of improved lifestyle against this risk. Information is lacking on the long-term mortality risks of different types of hip replacement surgery performed in the UK. The aim of this study was to compare 10-year mortality rates amongst patients undergoing hip resurfacing to those undergoing total hip replacement in England. Methods: Data were obtained from the English Hospital Episode Statistics (HES) database linked to Office for National Statistics (ONS) mortality records provided information on date and cause of death in all adults receiving elective primary hip replacement for OA in NHS hospitals in England between 1999 and 2012. The exposure of interest was prosthesis type classified as: total hip cemented, total hip uncemented, total hip unspecified fixation, and hip resurfacing. Confounding variables included age, gender, Charlson comorbidity index, rurality, and Index of Multiple Deprivation. The outcome was time from surgery to death (all cause mortality). Kaplan-Meier plots estimated the probability of survival up to 10 years following surgery. Cox regression modelling described the association of prosthesis type on time to death, adjusting for confounders. Propensity score matching was used to minimize the potential for confounding by indication. Results: Data were available on 429,806 patients receiving hip replacement. 263,916 (61.4%) were cemented, 121,144 (28.2%) uncemented, 26,147 (6.1%) unspecified and 18,599 (4.3%) hip resurfacing. Hip resurfacing was more common in younger patients and in men compared with other prosthesis types. Compared with cemented hip replacements, Cox regression models demonstrated a survival advantage in uncemented [hazard ratio (HR) 0.8695% CI (0.84, 0.88) and hip resurfacing (HR 0.52, 95% CI 0.47, 0.57) operations, after adjustment for confounders. There was no evidence of interaction between prosthesis type and age. To address the issue of confounding by indication, 12 576 hip resurfacing patients were propensity score matched to 3 comparable cemented hip replacements (37 728 patients). Kaplan Meier survival curves demonstrated that matched hip resurfacing patients had a much higher survival probability. Cox regression models on matched patients confirmed a lower risk of death in hip resurfacing patients vs cemented (HR 0.49, 95% CI 0.43, 0.55). Conclusions: Patients receiving hip resurfacing have reduced longterm mortality compared with patients receiving other types of hip replacement. This persisted after adjustment for confounding factors but the potential for residual confounding remains. Although patients receiving hip resurfacing are younger, there was no evidence of interaction with age. These findings require validation in external cohorts.