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Obesity and orthopaedic surgery
Harriet Lewis, Alexander Dodds and Mark Bowditch
At present 27% of adults in the UK are classified as obese and a further 36% are classified as overweight and this number is likely to increase significantly in the future [1]. Obesity is estimated to cost the NHS £3.2 billion annually.
The rise in the number of obese patients will have a significant impact on trauma and orthopaedic services in the UK, both in terms of the number of patients being referred, as well as the additional challenges associated with managing patients with obesity. The link between obesity and increased mechanical loading of joints leading to degeneration has been well documented. There are increased demands on the surgical team and provider of resources. In this article, we review challenges to orthopaedic practice with the rise in obesity rates, how obesity can affect operative practice and the use of restrictions on orthopaedic surgery based on body mass index (BMI).
Risks with orthopaedic surgery and raised BMI
Associated medical conditions such as diabetes, hypertension and cardiovascular issues as well as body habitus and venous access may make the anaesthesia more challenging. Regional anaesthetic has been shown to be more likely to fail in obese patients. The anaesthetist may face intra-operative problems due to decreased lung volume, collapse, and decreased chest wall compliance. Surgery in the obese patients will often be more challenging due to the distribution of fat and hence surgical access will be difficult. This in turn, can affect the technical aspects of surgery, such as the placement of pedicle screws in spinal surgery and implant alignment in knee surgery. Surgeons may need additional retractors for access, and surgery may take longer than normal. There is a link with increased post-operative complications following orthopaedic surgery, including wound infections, thromboembolism stroke and myocardial infarction. Venous thromboembolism risk may also be increased due to poor mobility and altered coagulation profiles. Longer-term, there is some evidence that there is a higher failure rate of orthopaedic implants in patients who are obese [2].
As with any orthopaedic intervention, the balance between the risks associated with the procedure and the benefits it provides have to be carefully considered and this is no different with obese patients. Despite the increased risks, obese patients with osteoarthritis can still greatly benefit through surgical intervention that still offer significant and effective pain relief and functional improvement. Evidence shows that there is a cost/QALY increase of £1,013 for a patient with a BMI greater of 40 compared to a £3,921 cost/QALY in patients less than 40, yet surgery still remains very cost effective3. Some surgeons will worry about how operating on patients with an increased risk profile could adversely affect their data such as the National Joint Registry (NJR) results. BMI should also be considered in context with other risk factors for surgery such as inflammatory arthropathy, and whilst BMI in itself may not be prohibitive for surgical intervention, it may be when combined with other risk factors.
Body mass index
Body mass index (BMI) is one of the most commonly used measures to assess a patient’s level of obesity. It is defined by weight (kg) divided by the square of the persons height (m2) (Kg/m2). The World Health Organisation defines obesity as being a BMI of more than 30. BMI is commonly used clinically as it is a quick and easy way of assessing an individual’s body composition. It has also been used as a research tool, and has been shown to be associated with health issues including cardiovascular disease, diabetes, renal disease and stroke.
Clinicians need to be aware of the limitations of BMI when it is being used to assess a patients risk for surgery. It is unable to distinguish between lean muscle weight and body fat. It also does not give any indication of the distribution of fat, and this could be critical for the orthopaedic surgeon.
Whilst central obesity may lead to a rise in a patient’s risk for medical complications, the distribution of fat on the limbs may be more relevant for an orthopaedic surgeon in terms of determining technical operative risk and post-operative complications such as infection. The two are different and often not present together. The British Orthopaedic Association has previously stated that BMI should not be used solely as a means to ration procedures such as total hip/knee replacement. This advice has also been given by other organisations including the American Medical Association.
BMI as a cut-off for referral access and surgery
Approximately two thirds of NHS England commissioning groups or integrated care systems have referral guidelines that include obesity limits using BMI. A guideline BMI figure of 40 or less is common but in some areas 35 has been used as a threshold for surgical intervention [4]. Health optimisation prior to planned surgical care is often indicated and generally beneficial but the reduction of BMI may not be that easy or indeed achieve a significant improvement in the risk:benefit balance. In some cases it may regarded as an inappropriate denial of care. Delaying surgery whilst patients try losing weight may in fact make them less ‘fit’ for surgery leading them to suffer increased pain and disability with further deconditioning. Organisations such as the BOA and RCSEng have stated that commissioning policies should be based on clinical need. Local referral restrictions for orthopaedic surgery based on BMI is not evidenced-based and the variation across the UK could be regarded as a ‘postcode lottery’.
A particular concern with the use of BMI to limit access to orthopaedic surgery is that obesity is associated with health inequalities. Individuals in lower socioeconomic groups are more likely to suffer with obesity, reflected in barriers to healthier food choice, lifestyle and exercise opportunities, and also problems with healthcare access. Using BMI as a measure to restrict access to orthopaedic services may in itself increase these health inequalities. Distribution of fat is linked to genetics, and those of Asian, Middle Eastern, African or African Caribbean inheritance are more prone to central obesity.
Furthermore, there is a gender difference in adipose tissue distribution, with men more likely to carry adipose tissue centrally. Patients from deprived areas of England and Wales are 69% less likely to have a hip replacement despite clinical need [5].
Pre-operative weight loss
One justification for the use of BMI cut offs for access to surgery is that it encourages weight loss in patients. National Institute for Health and Care Excellence (NICE) recognises the importance of a structured approach to preoperative weight management for individuals awaiting arthroplasty surgery.
This may include other surgical interventions including bariatric surgery. A recent study showed that patients who achieved weight loss pre-operatively showed a decrease reduction in complications including rate of VTE, infection and wound healing problems. The evidence is not clear and other studies have not reached the same conclusions [6]. Too rapid weight reduction may have adverse effects on surgical recovery.
Summary
Obesity will become a growing problem for trauma and orthopaedic surgery in the future. Surgeons need to be aware and plan for the issues with surgery in this patient group. However, patients will still get reliable improvements in pain and function with orthopaedic intervention. Tailoring surgical management options based on an individual patient characteristic is essential to optimise surgical outcomes. The use of BMI as a sole criterion to limit access to orthopaedic surgery is not evidence-based and should be challenged. Further research and policy revaluation is needed in this area.
References
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Rooshenas L, Ijaz S, Richards A, Realpe A, Savovic J, Jones T, et al. Variations in policies for accessing elective musculoskeletal procedures in the English National Health Service: A documentary analysis. J Health Serv Res Policy. 2022;27(3):190-202.
Wyatt S, Bailey R, Moore P, Revell M. Equity of access to NHS-funded hip replacements in England and Wales: Trends from 2006 to 2016. Lancet Reg Health Eur 2022;21:100475.
Seward MW, Briggs LG, Bain PA, Chen AF. Preoperative nonsurgical weight loss interventions before total hip and knee arthroplasty: a systematic review. J Arthroplasty. 2021;36(11):3796-806.e8.
Harriet Lewis is a Trauma and Orthopaedic Registrar, Severn Deanery.
Alexander Dodds is a Consultant Orthopaedic Surgeon, Gloucestershire Hospitals NHS FT Trust.
Mark Bowditch is a Consultant Orthopaedic Surgeon East Suffolk North Essex NHS FT Trust and is the BOA Vice President.
