Risk, optimisation and equitable access
This review was published in Orthopaedics and Trauma, which describes itself as providing “core clinical content for postgraduate training and continuing professional development”. Drawing on 136 references, the article synthesises current evidence on how obesity influences the perioperative risk profile, technical conduct, and short- and long-term outcomes of total hip arthroplasty. The risk obesity confers is argued to be graded rather than binary, so that surgical candidacy is better determined by comprehensive risk management than by categorical exclusion.
© 2025 Elsevier Ltd. All rights reserved. This article is not open access, and the full text is available via the publisher.
Abstract
Abstract condensed from the published article, which carries an unstructured abstract; the section headings above are editorial and the wording is otherwise as published.
Contents
01 · Background
Obesity accelerates the onset and progression of hip osteoarthritis through increased mechanical loading, systemic low-grade inflammation and metabolic dysregulation, amplifying pain, disability and healthcare use, which places it among the most important modifiable risk factors for the development and worsening of established disease.
The consequences are measurable at the level of the population as well as the joint, since obesity is responsible for early disability and morbidity and increases early mortality risk in an incremental fashion. Individuals with a body mass index of 30 to 35 kg/m² have median survival reduced by two to four years, while at 40 to 45 kg/m² the reduction is eight to ten years. World Health Organization estimates suggest that as of 2022 more than 890 million adults were living with obesity and a further 2.5 billion were overweight, and using current trends a predicted 3.8 billion adults could be overweight or obese by 2050.
Hip osteoarthritis accounts for a significant proportion of the global disease burden, with worldwide prevalence suggested to be 8.55% (95% CI 4.85–13.18) and predicted to rise significantly over the next 25 years, largely driven by ageing populations and increasing rates of obesity. An estimated one in four adults will develop symptomatic hip osteoarthritis in their lifetime, and total hip arthroplasty remains the mainstay of treatment for end-stage disease.
Demand is therefore projected to rise in a way that healthcare systems must plan for rather than react to. In the UK, projections from Farrow et al. indicate that demand for hip replacement will rise from 120/100,000/year in 2018 to 152/100,000/year in 2038, a 28% increase, while estimates from the USA forecast an increase in procedures of 176% by 2040 from 2019 levels, up to 719,364 operations annually. At current rates, over 55% of hip replacement patients will be obese by 2029, which has implications for how services allocate resources and where research effort could most usefully be directed.
Epidemiology & Demand
02 · Health Equity and Patient Selection
Obesity is disproportionately associated with particular population groups, with higher prevalence among individuals of low socio-economic status, within certain ethnic groups including Hispanics and African Americans, and among women, so that the groups already at greatest risk of developing osteoarthritis are also those most exposed to restrictive access criteria.
Many patients across the world still do not have reasonable access to hip replacement, and even in developed countries racial discrepancies exist, since African Americans are more likely to have severe hip osteoarthritis with worse pain and function yet are consistently less likely to undergo surgery. The issue is magnified when considered on a global scale, where establishing a service to diagnose and treat osteoarthritis requires investment in infrastructure, time and workforce training alongside sustainable supply chains for implants and consumables, so that access remains limited or restricted to urban centres in many regions.
The case for and against thresholds
The cycle of deferral
The clinical consequence of deferral is not neutral, because patients who defer surgery on the basis of their body mass index and associated risk factors often struggle to lose the required weight despite intention, which highlights the vicious cycle of inactivity, activity-related joint pain and inability to lose weight. Approximately 50% of patients who have a body mass index above 40 with moderate or severe osteoarthritis never return for a second clinic visit, and Foreman et al. reported that over 50% of patients with a body mass index above 40 with hip osteoarthritis who sought treatment are lost to follow-up. Those who persisted often eventually underwent surgery and were found to have a risk profile comparable to counterparts with a body mass index below 40, which suggests that a threshold may defer rather than reduce the risk it is intended to manage.
Current smoking status and poorly controlled diabetes, typically indicated by an elevated glycated haemoglobin, are frequently employed as criteria for the same purpose, and although both are associated with wound complications, prosthetic joint infection, delayed healing and higher revision rates, the evidence supporting the specific metrics in use is weaker than their application implies. While most centres use glycated haemoglobin as the cut-off metric, evidence suggests it is not a useful marker for predicting postoperative complications and that perioperative glucose may be a superior indicator of risk. Prolonged smoking cessation is likewise extremely difficult to achieve, with a lack of robust evidence to suggest that quitting briefly perioperatively imparts significant benefit.
03 · Perioperative Care
Preoperative optimisation is pivotal for successful surgery and when employed effectively can decrease the risk of complications and improve surgical outcomes, which matters particularly in a population where cardiovascular, metabolic and psychological co-morbidity is more prevalent.
Patients with hip and knee osteoarthritis frequently suffer from co-morbidities including hypertension, diabetes, obesity and depression, and the most targeted risk factors are obesity, anaemia, malnutrition and diabetes mellitus, although many other conditions associated with obesity can affect perioperative outcomes and should be checked preoperatively. Where feasible, optimisation of medical management through collaboration with the patient's general practitioner or relevant specialties is recommended preoperatively, and pre-admission clinics scheduled several weeks away from surgery can help ensure that no aspect of the patient's co-morbidity is unmanaged while giving an opportunity to carry out any final treatment or investigations.
Malnutrition is more prevalent in obese populations, with a fourfold increased likelihood of hypoalbuminaemia, which is associated with adverse outcomes in surgery, so referral to a nutritionist should be considered ahead of surgery and may form part of a wider dietary intervention to help facilitate preoperative weight loss. Although prehabilitation in obese populations undergoing hip replacement is relatively understudied, there is evidence to suggest that prehabilitation exercise regimes may improve postoperative length of stay and functional outcomes, and the pre-admission pathway also provides the opportunity to postpone surgery until risk is at an acceptable level for both patient and surgeon.
04 · Weight Loss
Weight loss is regularly recommended in clinical guidelines as a strategy to improve surgical readiness in obese patients scheduled for hip replacement, yet its impact on postoperative outcomes remains unclear. Obesity is strongly associated with adverse outcomes following hip replacement, while losing weight preoperatively may not confer a proportional reduction in risk corresponding to that weight loss.
Conservative measures to facilitate weight loss ahead of surgery include dietary interventions, exercise and behavioural therapy, and whilst these are effective, achieving and maintaining sufficient weight loss can often be difficult. Novel strategies such as glucagon-like peptide-1 receptor agonists have shown considerable promise in achieving sustained weight loss and may become an important adjunct in preoperative optimisation.
| Evidence | Design | Reported finding |
|---|---|---|
| Lau et al. | Systematic review of three randomized controlled trials | Favourable outcomes for patients who lost weight preoperatively, with significantly greater odds of having no complications after surgery than the control group (odds ratio 2.49, 95% CI 1.08 to 5.74; P = 0.03). |
| Laperche et al. | Large-scale retrospective cohort | No difference in 30-day adverse outcomes between obese patients who lost ≥10% of their bodyweight preoperatively and those who did not. |
| Schmerler et al. | Large-scale retrospective cohort | Significantly higher risks of medical complications, readmission and reoperation in both obese and normal-weight patients who lost weight before hip replacement. |
| Middleton et al. | Large-scale retrospective cohort | Increased complication and readmission rates in patients reducing from body mass index >40 to <40, compared with those remaining at body mass index >40. |
| Shul et al. | Cohort of morbidly obese patients | Weight loss 3 to 9 months preoperatively increased the risk of prosthetic joint infection (odds ratios 2.15 to 5.22, P < 0.001), whereas the risk decreased if weight loss occurred more than one year preoperatively (odds ratios 0.14 to 0.27, P < 0.005). |
| Palacios et al. | Systematic review and meta-analysis, bariatric surgery | Lower risk of periprosthetic fracture, shorter length of stay in hospital and fewer 30-day readmissions, but no significant improvement in overall complications including infection and all-cause revision. |
| Feng et al. | Meta-analysis, bariatric surgery | An increase in dislocation rates, but no significant change in any other aspect of the risk profile. |
| LaValva et al. | Comparative evidence | Body mass index reduction prior to hip replacement does not influence 90-day complications or readmissions, arguing that delaying surgery until patients meet certain criteria is an unnecessary restriction to beneficial surgery. |
Studies as cited in McCann et al. (2026). Findings are reported as described in the review; readers are referred to the primary publications for full methods and effect estimates.
It has been hypothesised that preoperative caloric restriction may induce a catabolic state, reducing physiological reserve and impairing the body's ability to respond to the metabolic and inflammatory stress of surgery, which could account for part of the discrepancy between the trial and cohort evidence. Understanding the physiological consequence of bariatric surgery ahead of hip replacement likewise remains unclear, and further research is required to characterise the benefits and risks, including implications for nutritional status and metabolism.
The timing of preoperative weight loss may play a more important role than previously thought, and these temporal differences may help account for the conflicting evidence, although more robust research is required. The optimal role and timing of weight-loss interventions within the surgical pathway underscores the need for more nuanced strategies that incorporate not only weight reduction, but also nutritional status, sarcopenia and overall functional capacity.
05 · Intraoperative Considerations
Obesity introduces several technical intraoperative challenges, since patient positioning, surgical exposure and prosthesis implantation are all more complex in this population, and implant selection often requires additional consideration.
Preparation, equipment and anaesthesia
Obese patients require tailored preparation and may need specialised bariatric equipment, including reinforced operating tables, hover mattresses, longer instruments and cell-saver systems, to accommodate greater body mass and reduce intraoperative strain. Close multidisciplinary communication between the surgical and anaesthetic teams is crucial, particularly to anticipate challenges with positioning, airway management and wound closure, while regional anaesthesia is often preferred where feasible and intraoperative measures such as pneumatic foot pumps for venous thromboembolism prophylaxis, intravenous antibiotics and tranexamic acid are strongly recommended to reduce complication risk.
Implant selection and stability
Obese patients generally place greater stresses per cycle upon implants and subsequently have poorer implant survival, so the largest femoral implant sizes that fit should be chosen for longevity, and modular stems should be avoided to minimise the risk of stem neck fracture. Undersizing components can be associated with increased risk of periprosthetic fracture and mechanical component failure, and since obesity also confers an increased risk of dislocation, this may be at least partially mitigated with the use of larger femoral heads or through use of dual mobility cups or lipped liners.
Component positioning and assistive technology
Correct implant positioning is more difficult to achieve in obese patients, and several strategies have been successfully employed to improve it. Yu et al. have shown improvement in acetabular component positioning in robotic-assisted hip replacement compared to manual surgery, and similar positive results have been reported by Zhang et al., who report improvements in the postoperative vertical centre of rotation and decreased variability of leg length differences using robotic-assisted techniques. Use of fluoroscopy intraoperatively may also be helpful, although it represents an additional resource requirement and has an associated learning curve.
Surgical approach
The optimal surgical approach remains controversial, and in the context of obesity excessive peri-incisional adiposity may create increased technical challenges. The anterior approach often has the smallest adiposity-related distance increase but has been associated with an increased risk of complications, and Salmons et al. report an increased risk of wound complications using the anterior approach compared to posterior or lateral, with an absolute risk of 3.6% versus 2.6% and a multivariable adjusted odds ratio of 1.5 (P < 0.001). Similar findings were reported by Shah et al., who suggest that in obese patients the direct anterior approach may carry a higher risk of prosthetic joint infection than other approaches, and on this basis many surgeons avoid anterior approaches in the obese patient, preferring posterior or lateral to allow for improved exposure.
The burden on the surgeon
The physiologic burden on surgeons during primary hip replacement significantly increases as patient body mass index increases, and since arthroplasty surgery is already associated with a high prevalence of work-related musculoskeletal injuries, the added physical demands of operating on obese patients may further elevate daily strain and injury risk. Recognising the greater physiologic strain placed on surgeons highlights the need for tailored intraoperative strategies and thoughtful operative scheduling, which is of increasing importance given the number of obese patients predicted to require hip replacement in future.
Care Pathway
Obesity confers a graded increase in perioperative risk following hip replacement, characterised by longer operative times, extended hospital stays, and higher rates of early complications and readmissions; however, these risks may be mitigated through surgical experience, operative efficiency and careful patient selection.
06 · Outcomes
Obesity has frequently been shown to be associated with increased risk of perioperative complications, although the nuanced nature of this relationship is only just being more clearly defined, and the pattern that emerges is one of graded rather than categorical risk.
A recent large-scale analysis of primary elective hip replacements performed between 2015 and 2021 demonstrated a non-linear association between body mass index and early postoperative complications, with risk increasing sharply beyond certain inflection points. Studies of the super-obese population with a body mass index above 50 show higher rates of most early postoperative complications compared to obese or morbidly obese counterparts, including venous thromboembolism, infection, blood transfusion, dislocation and readmission, which supports the concept of body mass index as a continuum of risk rather than a binary cut-off.
| Reported relationship | Threshold or gradient |
|---|---|
| Periprosthetic joint infection | Risk rose exponentially beyond a body mass index threshold of 37.4 |
| Surgical complications | Increased from a body mass index of 32 kg/m² |
| Medical complications | Increased from a body mass index of 39 kg/m² |
| Combined risk at the extreme | Up to 2.5-fold higher risk at a body mass index of 50 |
| Operative time | Increases by approximately 1 minute per 1 kg/m² over normal body mass index |
| Length of stay | Increases by 2.9% per 1 kg/m² over normal body mass index |
Figures as reported in McCann et al. (2026), drawing on the cited primary literature. Wang et al. reported that obesity class increased surgical time in a stepwise manner, from a mean of 74 minutes for normal-weight patients up to a mean of 97 minutes for obese class 3 patients.
Service models and surgeon experience
Day-case hip replacement has gained traction internationally as a safe and efficient model of care that reduces inpatient burden and improves service capacity, although given the longer operative times, length of stay and early postoperative outcomes in obese patients, same-day discharge is often less feasible and requires stringent patient selection and perioperative optimisation. High-volume surgeons demonstrate lower operative times, quicker time to discharge and a higher proportion of discharge to home, and some evidence suggests a lower complication rate in the morbidly obese population when surgery is carried out by more experienced surgeons. A specialist referral pathway for morbidly obese patients may therefore be helpful, although data in this area are mixed, and patient-reported outcomes and revision rates appeared to be independent of surgeon volume in at least one study.
Implant survivorship and revision
Obese patients undergoing hip replacement are at risk of earlier requirement for revision surgery, and a large systematic review and meta-analysis of over two million patients demonstrated that obese patients are at increased risk of complications, prosthetic joint infection and revision surgery compared with their normal-weight counterparts. In the meta-analysis by Haverkamp et al., both complication rate and implant survivorship were worse in the obese population, while subsidence appears to be more common and the greater load transmitted through the implant may predispose patients to higher rates of revision surgery.
Patient-reported outcomes
Despite increased medical and surgical postoperative risk, overweight and obese patients can achieve similar improvements in patient-reported outcome measures compared to normal-weight patients after hip replacement, and due to a reduced functional baseline their improvements may even exceed those seen in non-obese counterparts. In contrast to these findings, a large meta-analysis by Pozzobon et al. including both hip and knee arthroplasty patients demonstrated significantly worse functional outcomes in terms of pain and disability in obese patients undergoing joint replacement than in non-obese counterparts, so the balance of evidence supports meaningful benefit while cautioning against assuming equivalence.
Weight change after surgery
Theoretically, improvement in pain should permit overweight and obese patients to better engage in weight-loss endeavours, yet many studies including a systematic review by Inacio et al. showed no significant change in weight loss following arthroplasty surgery. Weight gain after arthroplasty may actually be more common than weight loss, although the evidence here remains mixed and the reasons for weight change following hip replacement are unclear, which suggests that surgery should not be presented to patients as a weight-loss intervention in its own right.
07 · Health Economics
The social and economic cost of patients who have end-stage osteoarthritis and are awaiting arthroplasty is significant, comprising direct costs such as pharmacological and surgical treatment and the use of hospital resources including complication management, alongside indirect costs including loss of productivity, absenteeism, early mortality and disability payments.
Economic evaluation of hip replacement has gained increasing attention in the orthopaedic literature, yet most studies remain limited to cost-identification analyses rather than rigorous cost-effectiveness or cost-utility assessments. A systematic review of 81 studies revealed that only 7% met minimum methodological standards for healthcare economic evaluation, with the majority focusing narrowly on perioperative hospital costs rather than lifetime costs or societal impact. Few studies incorporated long-term outcomes, indirect costs or discounting techniques, which are essential to accurately appraise the value of hip replacement within constrained healthcare systems.
Despite these limitations, the evidence consistently demonstrates that hip replacement is highly cost-effective, with the cost per quality-adjusted life year comparing favourably to other major health interventions such as coronary artery bypass grafting and renal dialysis. As demand continues to increase globally, a phenomenon driven by ageing populations, rising obesity rates and greater disease burden, the economic impact on health systems will intensify. Ensuring equitable access while maintaining cost efficiency will therefore require not only optimisation of perioperative outcomes but also the adoption of robust, standardised economic evaluation frameworks, and delays to accessing surgery should be minimised through robust patient pathways.
08 · Table 1
Table 1 reproduced from McCann et al. (2026), Orthopaedics and Trauma 40(1):31–41. THA, total hip arthroplasty; BMI, body mass index; HBA1c, glycated haemoglobin; OA, osteoarthritis; TXA, tranexamic acid; GLP1-RA, glucagon-like peptide-1 receptor agonist.
Practice Points
Practice points reproduced from the published article.
