Mixing of components from different manufacturers in total hip arthroplasty: prevalence and comparative outcomes

Abstract

Background and purpose — There have recently been highly publicized examples of suboptimal outcomes with some newer implant designs used for total hip replacement. This has led to calls for tighter regulation. However, surgeons do not always adhere to the regulations already in place and often use implants from different manufacturers together to replace a hip, which is against the recommendations of the Medicines and Healthcare Products Regulatory Agency (MHRA) and the directions of the manufacturers.

Patients and methods — We used data from the National Joint Registry of England and Wales (NJR) to investigate this practice.

Results — Mixing of components was common, and we identified over 90,000 cases recorded between 2003 and 2013. In the majority of these cases (48,156), stems and heads from one manufacturer were mixed with polyethylene cemented cups from another manufacturer. When using a cemented stem and a polyethylene cup, mixing of stems from one manufacturer with cups from another was associated with a lower revision rate. At 8 years, the cumulative percentage of revisions was 1.9% (95% CI: 1.7–2.1) in the mixed group as compared to 2.4% (2.3–2.5) in the matched group (p = 0.001). Mixing of heads from one manufacturer with stems from another was associated with a higher revision rate (p < 0.001). In hip replacements with ceramic-on-ceramic or metal-on-metal bearings, mixing of stems, heads, and cups from different manufacturers was associated with similar revision rates (p > 0.05).

Interpretation — Mixing of components from different manufacturers is a common practice, despite the fact that it goes against regulatory guidance. However, it is not associated with increased revision rates unless heads and stems from different manufacturers are used together.

All the authors were involved in the design of the study. Data management and analysis were undertaken by LH, KT, MP, and LH, and AB contributed to data interpretation. All the authors contributed to preparation of the manuscript.

Stryker and DePuy have funded other research undertaken by the University of Bristol.

We thank the patients and staff of all the hospitals who have contributed data to the National Joint Registry. We are grateful to the Healthcare Quality Improvement Partnership (HQIP), the National Joint Registry Steering Committee (NJRSC), and staff of the NJR Centre for facilitating this work. The views expressed are those of the authors and do not necessarily reflect those of the NJRSC or HQIP, who do not vouch for how the information is presented.

The sponsor of the study (The National Joint Registry) had no role in the study design, data collection, data analysis, data interpretation, or writing of the final report. LH had full access to all the data in the study and AB had final responsibility for the decision to submit the manuscript for publication.