Day case hip replacement in the NHS: a registry-based national cohort study

Osteoarthritis of the hip will affect around a quarter of people in their lifetimes, causing severe pain and disability. It can be successfully treated with a hip replacement, which show excellent results and last around 25 years.

However, in the last few years, NHS waiting lists have reached record levels, made worse by the COVID-19 pandemic. This has led to a large number of patients waiting for hip replacement enduring unnecessary pain, disability, and decline in mental and physical health.

One of the potential ways to increase the number of hip replacements we can do is to do more as a “day case”. This means that patients don’t stay overnight in hospital after the operation, but instead go home on the same day. Not everyone is suitable for a day case hip replacement – patients need to be chosen carefully.

Day case hip replacement first started in the USA, becoming more popular recently in the UK after the COVID-19 pandemic, where overnight hospital beds were limited. Small studies show that it appears to be safe, and patients seem satisfied with the process. However, with plans to rapidly expand how many day case joint replacements we are doing in the NHS, we need to look at the outcomes on a larger scale.

The main aims and objectives of the research study.

• Describe trends in day case joint replacement in England
• Analyse patient outcomes after day case hip replacement compared to traditional hip replacement

How this research is going to help address MSK health.

Recovering from the current backlog of orthopaedic procedures is likely to be one of the challenges of our generation. There is growing evidence from the US, Canada and Europe that hip replacement can be safely done as a day case operation. However, the healthcare systems of these countries are different to the NHS, and we cannot assume the results will be the same.

With all significant changes in the way that we practice, research is required to ensure that the changes are safe. The ambition of this project is to answer this important question by using data that is routinely collected by all hospitals in England. This will give us data on a National level.

If the results following day case surgery are worse, then the practice will need to change based on what we find. This could be who we are selecting for day case surgery, for example. If results are the same or better, then increasing how much day case surgery we are offering might be one of the ways we are able to reduce waiting times. 

The main research methods, or datasets being used.

The National Joint Registry (NJR) is the largest joint replacement registry in the world. It records data on all hip replacements done in England, Wales, Northern Ireland, the Isle of Man and Guernsey.

Data from the NJR can be linked to Hospital Episode Statistics (HES). HES records information on all NHS hospital admissions in England. Combining these two datasets together gives us far more detail and allows us to identify all day case hip replacements done in England.

We will describe demographic data i.e. the characteristics of people who are able to undergo day case hip replacement, including age, sex, medical conditions, frailty, socioeconomic factors, as well as surgical factors such as the approach to the hip joint, use of cement, hip replacement materials, and type of anaesthetic.

Patients who are readmitted after surgery to any NHS hospital in England will be picked up by the HES dataset. Readmissions for day case patients will be compared with those who stayed in hospital for one to two days. Any differences in patient and surgical characteristics will be adjusted for in the statistical analysis to ensure comparisons are as fair as possible.

As well as readmissions, we will look for differences in reoperations between the two groups. These will include operations not typically picked up in the NJR data such as closed reduction of dislocations, and fixation for peri-prosthetic fracture (where the bone breaks around the artificial hip).

In a similar manner, to assess safety we will also compare the rate of serious medical events between the two groups, such as heart attack, stroke, deep vein thrombosis and pulmonary embolism, pneumonia, and death.

Research results generated.

We are still in the analysis stage and have no firm results from the main analysis yet.

Next steps of this research project.

The background work to this project involved systematically searching for all studies that have been done before on day case joint replacement. The results of these were analysed together (meta-analysis) showing that day case joint replacement appears to be safe, but there is a lack of NHS studies. This paper is currently under review having been accepted with changes.

NJR data has been analysed to show the number of joint replacements we have lost as a result of the COVID-19 pandemic, and whether we are on the road to recovery. This article is in press with the Bone & Joint Journal.

HES data is routinely collected primarily for NHS Hospitals to receive funding for services provided. It therefore needs to be carefully “cleaned” before it can be used for research. This is a long process which is currently underway.

Once the cleaning process is completed, the main analysis can begin. This will consist of fitting and testing statistical models of increasing complexity to answer the questions described.

Impact of this Orthopaedic Research UK fellowship on your research and career

This fellowship has been invaluable in allowing me to pause my usual clinical practice and focus on answering this important clinical question full-time.

Researcher: Jonathan French

Supervisor(s): Kevin Deere, Adrian Sayers, Katie Whale, Michael Whitehouse

University or Trust: University of Bristol

Award stream: MSK Grand Challenge Award

Award duration: 2 years

Amount rewarded: £110,000

Other funders: British Hip Society

Collaborations/ partners: British Hip Society