Research identifies best materials for long-lasting hip implants

Hip implants with a delta ceramic or oxidized zirconium head and highly crosslinked polyethylene liner or cup had the lowest risk of revision during the 15 years after surgery, a new study led by the University of Bristol has found. The research could help hospitals, surgeons and patients to choose what hip implant to use for replacement surgery.

The aim of the study was to establish hip implant materials at risk of revision to help orthopedic surgeons, and patients, and to improve shared decision making before surgery by identifying hip implants with the lowest risk of revision.

The independently conducted research, published in PLOS Medicine today [7 November], was funded by CeramTec and was supported by the National Institute for Health and Care Research (NIHR) and the NIHR Bristol Biomedical Research Centre (Bristol BRC).

The researchers analyzed National Joint Registry (NJR) data from 1,026,481 hip replacement patients carried out in the NHS and private sectors in England and Wales for up to 15 years after initial hip replacement operations (between 2003 to 2019). 

After reviewing hip implants from the NJR data, the research team found the risk of revision following a hip replacement is influenced by the type of material used in the bearing surface. Bearing surfaces are the moving parts of an artificial hip joint that glide against each other during activity.

The data indicated hip implants with a delta ceramic or oxidised zirconium head and highly crosslinked polyethylene liner or cup had the lowest risk of revision throughout the 15 years following hip replacement surgery.

These findings were confirmed when the research team investigated the specific reasons for revision hip replacements being performed. The data also showed 20,869 (2 per cent) of hip replacement patients had to undergo revision after the initial surgery.

Dr Erik Lenguerrand, Senior Lecturer in Medical Statistics and Quantitative Epidemiologist in the Bristol Medical School: Translational Health Sciences (THS) at the University of Bristol, and a senior author on the paper, said: "Our research has found the risk of hip replacement revision depends on the hip implant materials used in the original surgery. The lowest risk of revision are from implants with delta ceramic or oxidised zirconium head and a highly crosslinked polyethylene (HCLPE) liner or cup.

"Further research is needed to find out the association of implant materials with the risk of rehospitalization, re-operation other than revision, mortality and the cost-effectiveness of these materials."

Michael Whitehouse, Professor of Trauma and Orthopaedics at Bristol Medical School: THS, and senior clinical lead for the paper, explained: "Our study has used data from one of the largest registries in the world that includes all public and private health care sectors in England and Wales. This means that the data is more generally applicable than that available previously, which was limited by broad groupings of implant types or much smaller study size. It highlights the importance of considering the whole structure that is created when implants are put together to make up a hip replacement rather than focusing on individual components.

"Our findings will help hospitals, surgeons and patients to choose hip implants and combinations of them with the lowest risk of revision following an initial hip replacement operation."

We are always delighted when the data from the NJR can be used by researchers to produce important research of this kind which gives meaningful analysis to guide surgeons and patients in their decisions. An important value of the NJR data is that it allows researchers a unique insight to assess the long-term performance of different hip implant materials.

By tracking the combinations of materials used and subsequent revision rates, this research highlights the role of implant material choice in surgical outcomes. This ensures that the materials used can be optimized for longevity and patient health. Surgeons would be well advised to study these findings carefully in relation to the implant choices they make, and to use the information in pre-operative discussions with their patients. As the demand for joint replacements continues to rise, this insight can be invaluable in reducing revision surgery."

Tim Wilton, Medical Director of the National Joint Registry (NJR)

The research was not a randomized controlled trial and therefore it was not possible to control all factors that can influence the risk of revision.

The categorization of hip implants used as part of hip replacements is often broad in national joint replacement surgery registries and does not fully show differences in revision risks associated within the different types of implant materials grouped together.

Joint replacement surgery is used to treat a variety of musculoskeletal problems including osteoarthritis and acute trauma is a common and very effective surgical procedure, with over 110,000 performed annually in the United Kingdom. By 2060, the demand for joint replacement will increase by almost 40 per cent from current levels. Joint replacements are long-lasting, with over half of hip and knee replacements lasting over 25 years.

The research team would like to thank the patients and staff of all the hospitals in England, Wales, and Northern Ireland who have contributed data to the NJR, along with the Healthcare Quality Improvement Partnership, the NJR Research Committee, and staff at the NJR for facilitating the research.