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The role of hospital organisation, surgical factors, and the enhanced recovery pathway, on patient outcomes and NHS costs following primary hip and knee replacement surgery: spatial and longitudinal analysis of routine data


Osteoarthritis is a leading cause of pain and disability. Many people with severe hip or knee pain caused by osteoarthritis have an operation called total joint replacement. This involves replacing the painful hip or knee joint with an artificial joint. Over 150,000 hip and knee replacement operations take place each year in the NHS and this number is expected to increase.

Outcomes of surgery will vary across different hospitals and areas of the country. This may be explained by a hospital treating more complex and sicker patients. However, differences in patient outcomes could also be explained by how hospitals organise their services, such as bed availability, numbers of operating theatres and specialist surgeons, using new surgical techniques, or centralising care into specialist high volume hospitals.

A new patient pathway for hip and knee replacement called enhanced recovery has been introduced in NHS and private hospitals. It is hoped this will benefit patients, through patient education before and after surgery, that includes making changes around the home, exercises to strengthen the joint and changes to diet, to help reduce the risk of complications and speed up a patient’s recovery time. For patients in whom it is suitable, they will further benefit by being able to return home earlier to continue their recuperation at home with appropriate support. This in turn will benefit the hospital by freeing up space for other patients on the waiting list. However, hospitals organise enhanced recovery services in different ways and it is unclear which way is best.

Large datasets from the National Joint Registry (NJR) alongside data from NHS Digital will be used during this study.  The personal identifiers of patients who had hip or knee replacement surgery and consented for their details to be stored in the NJR will be securely transferred to NHS Digital.  NHS Digital will link the data to information it collects and extract details of all hospital admissions (HES)for the study cohort and Patient Recorded Outcome Measures (PROMS).  NHS Digital will securely transfer the linked data to the University of Oxford as pseudonymised data (i.e. all identifiers will be removed and replaced with a unique patient ID).  The NJR will securely transfer pseudonymised information from its records to the University of Oxford using the same unique ID so that the data can be linked by the University of Oxford and processing in such a way that researchers will not be able to identify patients.


  1. Identification of hospital organisation, surgical factors, and the enhanced recovery pathway as determinants of geographical variation in patient outcomes and NHS costs. 
  2. Natural experiment to determine the clinical and cost-effectiveness of the enhanced recovery treatment pathway
  3. Qualitative study (process evaluation) on implementation of enhanced recovery pathways in four hospital settings

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