This is a plain English summary of an original research article
A commonly used, cheaper implant used in total hip replacement surgery is as effective as more expensive options for over-65s, a new study has found.
A range of prosthetic implants is used for hip replacement, including newer and more expensive options, with different surface materials and some that do not require cement. They may wear at different rates, and all can require further surgery if they become loose. This risk is greater for younger and more active patients.
This large NIHR-funded economic study analysed data from national joint registries in the UK and Sweden to compare the lifetime cost-effectiveness of hip replacement for men and women of different ages in the UK. For older patient groups, there was no evidence that newer, more expensive implants would be more effective. For under-65s, a newer type of implant was more cost-effective, but the picture was less clear.
These findings will be of interest to patients, surgeons and healthcare commissioners who can take several considerations and preferences in the choice of implant.
Why was this study needed?
Total hip replacement (THR) is one of the most frequently performed surgeries in the UK and around the world. In 2017 there were a total of 94,184 procedures performed in England and Wales.
‘Metal-on-polyethylene’ is the most commonly used type of implant, and has been successfully used since the 1950s. However, the polyethylene component wears with increased physical activity and load, resulting in loosening and bone loss over time. This can mean that patients have to undergo further revision surgery.
Newer, more expensive, options have been developed to improve long-term patient outcomes, which may be especially relevant for younger patients. Different surface combinations include: ‘ceramic-on-polyethylene’, ‘ceramic-on-ceramic’, and ‘metal-on-metal’. There are also different ways of fixing the implants to the bone, and different head sizes.
This study, which builds on previous ones, improves our knowledge about the long-term cost-effectiveness of different types of implant for different patient groups.
What did this study do?
This economic modelling study compared 24 different implant combinations currently used in clinical practice against the most commonly used, cheapest implant in the UK (small-head, cemented, metal-on-polyethylene).
The researchers analysed more than 1 million individual patient-records from national joint registries in the UK and Sweden, countries with similar publicly funded health services. They looked at sub-groups of men and women of different ages to estimate the likelihood that their THR would fail and they would need revision surgery. They used this data in a Markov model to compare the cost-effectiveness of each type of replacement for different age groups using approved UK methods and thresholds for “value”.
There was a small risk of selection bias, as the study used observational data, which means that surgeons may be more likely to choose certain combinations for certain patients. However, this was a large sample size with robust model design, so the results are thought to be reliable.
What did it find?
- Small-head cemented metal-on-polyethylene implants were the most cost-effective for men and women older than 65 years (80% probability of being an accurate estimate for those over 75). This is the cheapest implant type, at around £750, and displays some of the lowest risks of revision surgery for older men and women. It is currently used in around 30% of THRs.
- Small-head cemented ceramic-on-polyethylene implants were most cost-effective in men and women younger than 65 years, but these results were more uncertain, mainly because it was harder to estimate the risk of revision surgery for these groups.
- The review found no evidence that uncemented, hybrid, or reverse hybrid implants were the most cost-effective option for any patient group, due to higher costs or higher revision rates.
- Across all sub-groups, large-head implant combinations were not cost effective.
What does current guidance say on this issue?
NICE guidance says that THR should only be recommended for treatment of end-stage osteoarthritis of the hip if the prostheses have rates of failure (or projected rates of failure) of 10% or less at 10 years or, as a minimum, a three-year revision rate consistent with this.
A patient’s age, activity levels, medical history and the surgeon’s preferences and experience of using a particular type of implant should be taken into consideration. While NICE doesn’t recommend a particular type of implant, it does warn that metal-on-metal implants may be associated with soft tissue damage.
What are the implications?
This is a useful study looking at the cost-effectiveness of different implants in use with short and longer-term risk of revision with large patient numbers. Although the evidence to date doesn’t support large scale spending on new types of implant, clinical practice is changing worldwide, particularly in Australia and the US, and further data may become available in the coming years which could change this assessment.
Rigorous randomised trials with long-term follow up will be needed to assess the effectiveness of new types of implant, particularly for the under-65s. As the number of THRs performed every year continues to increase, the lifetime cost-effectiveness of the implants is key for both patients and healthcare commissioners.
Citation and Funding
Fawsitt C, Thom H and Hunt L. Choice of prosthetic implant combinations in total hip replacement: cost-effectiveness analysis using UK and Swedish hip joint registries data. Value in Health. 2019;22(3):303-12.
This study was funded by the NIHR Research for Patient Benefit Programme (project number PB-PG-0613-31032).
NICE. Total hip replacement and resurfacing arthroplasty for end-stage arthritis of the hip. TA304. London: National Institute for Health and Care Excellence; 2014.
National Joint Registry. Types of primary hip replacements undertaken. London: National Joint Registry UK, 2018.
Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre