As an orthopaedic surgeon, I have developed a particular interest in hospital readmissions after hip replacement and knee replacement surgery.

These are two of the most commonly performed elective surgical procedures and are increasing in frequency as the population ages. Readmission rates have gained attention for their role as a performance metric linked to financial reimbursement, both in the NHS and elsewhere. For their punitive use, the presumption is that early readmission (usually taken to be within 30 days of discharge) signifies that either the discharge was premature, discharge arrangements were inappropriate, or the quality of hospital care was substandard. But is this fair?

Some ‘big data’ analysis I worked on, using a technique known as multilevel modelling, exposed the complex interplay of factors predicting readmission including patient factors, surgeon factors and hospital factors. Each of these leaves its own ‘footprint’ on the likelihood of early readmission.

However, what I realised was that whilst factors such as patient age and co-morbidities (e.g. diabetes, high blood pressure) are easy to define, and it is relatively easy to audit whether in-hospital care was delivered to a satisfactory standard (e.g. if the correct medication was prescribed, the surgery done was on time, the correct documentation was completed), it is much more difficult to evaluate the care people receive outside of the hospital environment.

Most people who have a knee replacement do not need domiciliary care when they go home… but for patients admitted after an emergency (e.g. a hip fracture, chest infection or stroke) a far higher proportion have significant changes in their care needs.

Quantifying how appropriate care is in this situation is a daunting task. How do we account for the role of informal carers, such as family and friends? What if an individual’s care needs change after they leave hospital, when they realise they cannot cope? Are the number of hours of care or ‘quality’ of care (assuming we can agree on what this means) more important in determining readmission risk?

The issue of readmission, which costs the NHS over £1.6 billion per year, highlights how ‘health care’ and ‘social care’ cannot be disentangled. And this is just the tip of the iceberg. Unless we can develop better ways of tracking individuals’ care needs, in real-time, and matching this to available supply (including not just formal domiciliary care but many of the ancillary services people need), as a health system we are missing an opportunity not only to improve patient care but to lower costs.

Please note that the views expressed here are those of the author alone and not necessarily those of any other person or organisation