Mortality and implant revision rates of hip arthroplasty in patients with osteoarthritis: registry based cohort studyBMJ 2012; 344 doi: https://doi.org/10.1136/bmj.e3319 (Published 14 June 2012) Cite this as: BMJ 2012;344:e3319
- D J W McMinn, consultant orthopaedic surgeon1,
- K I E Snell, PhD student2,
- J Daniel, director of research1,
- R B C Treacy, consultant orthopaedic surgeon3,
- P B Pynsent, director of research and teaching centre3,
- R D Riley, reader in biostatistics4
- 1McMinn Centre, Edgbaston, Birmingham B15 3DP, UK
- 2MRC Midlands Hub for Trials Methodology Research, School of Health and Population Sciences, University of Birmingham, Birmingham B15 2TT
- 3Royal Orthopaedic Hospital, Northfield, Birmingham B31 2AP
- 4School of Health and Population Sciences, University of Birmingham, Birmingham B15 2TT
- Correspondence to: R D Riley
- Accepted 25 April 2012
Objectives To examine mortality and revision rates among patients with osteoarthritis undergoing hip arthroplasty and to compare these rates between patients undergoing cemented or uncemented procedures and to compare outcomes between men undergoing stemmed total hip replacements and Birmingham hip resurfacing.
Design Cohort study.
Setting National Joint Registry.
Population About 275 000 patient records.
Main outcome measures Hip arthroplasty procedures were linked to the time to any subsequent mortality or revision (implant failure). Flexible parametric survival analysis methods were used to analyse time to mortality and also time to revision. Comparisons between procedure groups were adjusted for age, sex, American Society of Anesthesiologists (ASA) grade, and complexity.
Results As there were large baseline differences in the characteristics of patients receiving cemented, uncemented, or resurfacing procedures, unadjusted comparisons are inappropriate. Multivariable survival analyses identified a higher mortality rate for patients undergoing cemented compared with uncemented total hip replacement (adjusted hazard ratio 1.11, 95% confidence interval 1.07 to 1.16); conversely, there was a lower revision rate with cemented procedures (0.53, 0.50 to 0.57). These translate to small predicted differences in population averaged absolute survival probability at all time points. For example, compared with the uncemented group, at eight years after surgery the predicted probability of death in the cemented group was 0.013 higher (0.007 to 0.019) and the predicted probability of revision was 0.015 lower (0.012 to 0.017). In multivariable analyses restricted to men, there was a higher mortality rate in the cemented group and the uncemented group compared with the Birmingham hip resurfacing group. In terms of revision, the Birmingham hip resurfacings had a similar revision rate to uncemented total hip replacements. Both uncemented total hip replacements and Birmingham hip resurfacings had a higher revision rate than cemented total hip replacements.
Conclusions There is a small but significant increased risk of revision with uncemented rather than cemented total hip replacement, and a small but significant increased risk of death with cemented procedures. It is not known whether these are causal relations or caused by residual confounding. Compared with uncemented and cemented total hip replacements, Birmingham hip resurfacing has a significantly lower risk of death in men of all ages. Previously, only adjusted analyses of hip implant revision rates have been used to recommend and justify use of cheaper cemented total hip implants. Our investigations additionally consider mortality rates and suggest a potentially higher mortality rate with cemented total hip replacements, which merits further investigation.
This dataset was provided by the National Joint Registry for England and Wales. The views expressed represent those of the authors and do not necessarily reflect those of the National Joint Registry steering committee. We thank the two reviewers and the BMJ manuscript meeting committee for their helpful comments that have helped to considerably improve this paper.
Contributors: DJWMcM, JD, and RBCT observed clinical and registry differences and developed the idea for the paper, provided clinical input, and wrote extensive parts of the narrative. PBP provided initial statistical analyses and continued subsequent statistical and editorial advice. KIES undertook all data cleaning, performed all statistical analyses, produced all the table and figures, and helped to draft and revise the paper. RDR devised the statistical analysis plan, undertook initial statistical analyses, supervised the work done by KIES, wrote most of the first article draft, and helped to revise it accordingly. RDR is guarantor.
Funding: KIES is funded by the MRC Midlands Hub for Trials Methodology Research at the University of Birmingham (Medical Research Council Grant ID G0800808). RDR is also supported by funding from this Hub.
Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: DJWMcM and RBCT were designers of Birmingham hip resurfacing and were shareholders in Midland Medical Technologies before the company was sold to Smith and Nephew in 2004. DJWMcM is an unpaid consultant to Smith and Nephew Orthopaedics UK. The McMinn Centre receives institutional research funding for specific research projects but no funding has been received for the research or preparation of this manuscript.
Ethical approval: Not required. Existing anonymised data was used for this study.
Data sharing: This dataset was made available by the National Joint Registry for England and Wales.
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