Economic burden of obesity in primary total knee arthroplasty

Remote Delivery of Partial Meal Replacement for Weight Loss in People Awaiting Arthroplasty

Background: Obesity is linked to higher rates of complications; lower absolute recovery of mobility, pain, and function; and increased costs of care following total knee or hip arthroplasty (TKA, THA). The aim of this prospective cohort study was to evaluate the effectiveness of a 12-week partial meal replacement (PMR) weight loss program for people awaiting TKA or THA and living with obesity (body mass index (BMI) ≥ 30 kg/m2). Methods: The intervention was delivered remotely and included a 12-week PMR plan of 1200 calories/day, incorporating two meal replacement shakes/soups and a third suitable simple meal option. The intervention support was provided through online group education sessions, one-to-one teleconsultation with a dietitian, and access to a structured PMR App with functions for goal setting and providing educational content on diet, physical activity, and behaviour changes. Results: Of the 182 patients approached, 29 provided consent to participate, 26 participants commenced the program, and 22 participants completed the 12-week PMR plan. Completers exhibited statistically significant weight loss from baseline to 12 weeks, with a paired difference of 6.3 kg (95% CI: 4.8, 7.7; p < 0.001), with 15 out of 22 (68.2%) participants achieving at least 5% weight loss. Statistically significant reductions in HbA1c and low density lipoprotein (LDL) were observed at 12 weeks compared to baseline. Moreover, a significant increase in the proportion of participants in the action and maintenance phases of the readiness to change diet, physical activity, and weight were observed at 12 weeks. The majority of program completers (18 out of 22) expressed willingness to pay for the service if offered on a long-term basis following the arthroplasty. Conclusions: This study's findings demonstrated that significant weight loss is achievable for people living with obesity awaiting arthroplasty following a 12-week PMR weight loss program. The remote delivery of the intervention was feasible and well accepted by people awaiting TKA or THA.

Global mapping of institutional and hospital-based (Level II-IV) arthroplasty registries: a scoping review

PURPOSE

Four joint arthroplasty registries (JARs) levels exist based on the recorded data type. Level I JARs are national registries that record primary data. Hospital or institutional JARs (Level II-IV) document further data (patient-reported outcomes, demographic, radiographic). A worldwide list of Level II-IV JARs must be created to effectively assess and categorize these data.

METHODS

Our study is a systematic scoping review that followed the PRISMA guidelines and included 648 studies. Based on their publications, the study aimed to map the existing Level II-IV JARs worldwide. The secondary aim was to record their lifetime, publications' number and frequency and recognise differences with national JARs.

RESULTS

One hundred five Level II-IV JARs were identified. Forty-eight hospital-based, 45 institutional, and 12 regional JARs. Fifty JARs were found in America, 39 in Europe, nine in Asia, six in Oceania and one in Africa. They have published 485 cohorts, 91 case-series, 49 case-control, nine cross-sectional studies, eight registry protocols and six randomized trials. Most cohort studies were retrospective. Twenty-three per cent of papers studied patient-reported outcomes, 21.45% surgical complications, 13.73% postoperative clinical and 5.25% radiographic outcomes, and 11.88% were survival analyses. Forty-four JARs have published only one paper. Level I JARs primarily publish implant revision risk annual reports, while Level IV JARs collect comprehensive data to conduct retrospective cohort studies.

CONCLUSIONS

This is the first study mapping all Level II-IV JARs worldwide. Most JARs are found in Europe and America, reporting on retrospective cohorts, but only a few report on studies systematically.

The regulatory challenge of 3D bioprinting

New developments in additive manufacturing and regenerative medicine have the potential to radically disrupt the traditional pipelines of therapy development and medical device manufacture. These technologies present a challenge for regulators because traditional regulatory frameworks are designed for mass manufactured therapies, rather than bespoke solutions. 3D bioprinting technologies present another dimension of complexity through the inclusion of living cells in the fabrication process. Herein we overview the challenge of regulating 3D bioprinting in comparison to existing cell therapy products as well as custom-made 3D printed medical devices. We consider a range of specific challenges pertaining to 3D bioprinting in regenerative medicine, including classification, risk, standardization and quality control, as well as technical issues related to the manufacturing process and the incorporated materials and cells.

A Novel Method for Stratification of 30-Day Major Complication Risk Using Body Mass Index Thresholds for Patients Undergoing Total Knee Arthroplasty: A National Cohort of 443,157 Patients

INTRODUCTION

Many organizations have utilized pre-established body mass index (BMI) cut-offs to guide surgical decision making. As there have been many improvements in patient optimization, surgical technique, and perioperative care over time, it is important to reassess these thresholds as well as contextualize them to total knee arthroplasty (TKA). The purpose of this study was to calculate data-driven BMI thresholds that predict significant differences in risk of 30-day major complications following TKA.

METHODS

Patients who underwent primary TKA from 2010 to 2020 were identified in a national database. Stratum-specific likelihood ratio (SSLR) methodology was utilized to determine data-driven BMI thresholds at which the risk of 30-day major complications increased significantly. These BMI thresholds were tested using multivariable logistic regression analyses. A total of 443,157 patients were included, who had a mean age of 67 (range, 18 to 89), mean BMI of 33 (range 19 to 59), and 11,766 (2.7%) of patients had a 30-day major complication RESULTS: SSLR analysis identified four BMI thresholds that were associated with significant differences in 30-day major complications: 19 to 33, 34 to 38, 39 to 50, and 51+. When compared to those who had a BMI between 19 and 33, the odds of sustaining a major complication sequentially and significantly increased by 1.1, 1.3, and 2.1 times (p<0.05 for all) for the other thresholds.

CONCLUSION

This study identified four data-driven BMI strata utilizing SSLR analysis that were associated with significant differences in the risk of 30-day major complications following TKA. These strata can be utilized to guide shared decision making in patients undergoing TKA.

Clinical Pathways of Patients Denied Total Knee Arthroplasty Due to an Institutional BMI Cutoff

Out of concern for the increased risk of complications with morbid obesity, institutional body mass index (BMI) cutoffs for total knee arthroplasty (TKA) have become commonplace. We sought to answer the questions: what percentage of morbidly obese patients with knee osteoarthritis who present to an arthroplasty clinic will, within 2 years, undergo TKA at (1) a BMI less than 40 kg/m² or (2) at a BMI greater than 40 kg/m²? Of those who do not undergo surgery, (3) what percentage lose enough weight to become TKA-eligible, and (4) what percentage do not? We performed an observational study of 288 patients, of which 256 had complete follow-up. Institutional electronic medical record review and patient follow-up by telephone were conducted to determine which patients underwent surgery, and at what BMI. For those that did not undergo TKA, BMI was examined to see if the patient ever lost enough weight to become TKA eligible. Twelve of 256 patients (4.7%) underwent TKA at a BMI less than 40 kg/m², 64 patients (25%) underwent TKA at a BMI greater than 40 kg/m², and 7 patients (2.7%) underwent surgery at an outside hospital. The average BMI at the time of surgery was 42.3 kg/m². Thirty-seven of 256 patients (14.4%) lost enough weight to become TKA-eligible within 2 years of the initial visit but did not undergo surgery, while 136 patients (53.1%) neither underwent TKA nor became eligible. Strict enforcement of a BMI cutoff for TKA is variable among surgeons. In the absence of weight loss protocols, 19.1% of morbidly obese patients may be expected to reach the sub-40 kg/m² BMI milestone.

An Integrated Cost Model Based on Real Patient Flow: Exploring Surgical Hospitalization

Considering the gap observed in studies on health costs, this article aims to propose a cost calculation model for surgical hospitalization. A systematic literature review using PRISMA was conducted to map cost drivers adopted in similar studies and provide theoretical background. Based on the review, an integrated model considering real patient flow was developed using CHEERS guidelines. The micro-costing top-down method was adopted to develop the cost model allowing a balance between the accuracy of the information and the feasibility of the cost estimate. The proposed model fills two gaps in the literature: the standardization of a cost model and the ability to assess a vast number of different surgery costs in the same hospital. Flexibility stands out as an important advantage of the proposed model, as its application enables evaluation of elective and urgent surgeries of medium and high complexity performed in public and private hospitals. As a limitation, the hospital should have hospital information and cost systems implemented. The proposed cost model can provide important information that can result in better decision making. This becomes more relevant in public health, especially in low- and middle-income countries, which faces a lack of resources and whose positive effects can improve healthcare.

Projected Prevalence of Obesity in Primary Total Knee Arthroplasty: How Big Will the Problem Get?

BACKGROUND

Obesity is a well-established risk factor for complications following primary total knee arthroplasty (TKA). The purpose of this study is to utilize 3 national databases to develop projections of obesity within the general population and primary TKA patients in the United States through 2029.

METHODS

Data from the National Surgical Quality Improvement Program (NSQIP), the Behavior Risk Factor Surveillance System (BRFSS), and the National Health and Nutrition Examination Survey were queried for years 1999-2019. Current Procedural Terminology code 27447 was used to identify primary TKA patients in NSQIP. Individuals were categorized according to body mass index (kg/m²) by year: normal weight (≤24.9); overweight (25.0-29.9); obese (30.0-39.9); and morbidly obese (≥40). Multinomial logistic regression was used to project categorical body mass index data for years 2020-2029.

RESULTS

A total of 8,372,221 individuals were included (7,986,414 BRFSS, 385,807 NSQIP TKA). From 2011 to 2019, the prevalence of normal weight and overweight individuals declined in the general population (BRFSS) and in primary TKA. Prevalence of obese/morbidly obese individuals increased in the general population from 31% to 36% and in primary TKA from 60% to 64%. Projection models estimate that by 2029, 46% of the general population will be obese/morbidly obese and 69% of primary TKA will be obese/morbidly obese.

CONCLUSION

By 2029, we estimate ≥69% of primary TKA to be obese/morbidly obese. Increased resources dedicated to care pathways and research focused on improving outcomes in obese arthroplasty patients will be necessary as this population continues to grow.

LEVEL OF EVIDENCE

Level III, Retrospective Cohort Study.

Are Body Mass Index Cutoffs Creating Racial, Ethnic, and Gender Disparities in Eligibility for Primary Total Hip and Knee Arthroplasty?

BACKGROUND

Unabated increases in the prevalence of obesity among American adults have disproportionately affected women, Black persons, and Hispanic persons. The purpose of this study was to evaluate for disparity in rates of patient eligibility for primary total hip arthroplasty (THA) and total knee arthroplasty (TKA) based on race and ethnicity and gender by applying commonly used body mass index (BMI) eligibility criteria to two large national databases.

METHODS

We retrospectively reviewed data from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database for the years 2015-2019 for primary THA and TKA and the National Health and Nutrition Examination Survey (NHANES) from 2011-2018. Designations of race and ethnicity were standardized between cohorts. BMI cutoffs of <50 kg/m², <45 kg/m², <40 kg/m², and <35 kg/m² were then applied. Rates of eligibility for surgery were examined for each respective BMI cutoff and stratified by age, race and ethnicity, and gender.

RESULTS

143,973 NSQIP THA patients, 242,518 NSQIP TKA patients, and 13,255 NHANES participants were analyzed. Female patients were more likely to be ineligible for surgery across all cohorts for all modeled BMI cutoffs (P < .001 for all). Black patients had relatively lower rates of eligibility across all cohorts for all modeled BMI cutoffs (P < .0001 for all). Hispanic patients had disproportionately lower rates of eligibility only at a BMI cutoff of <35 kg/m².

CONCLUSION

Using BMI cutoffs alone to determine the eligibility for primary THA and TKA may disproportionally exclude women, Black persons, and Hispanic persons. These data raise concerns regarding further disparity and restriction of arthroplasty care to vulnerable populations that are already marginalized.

LEVEL OF EVIDENCE

Retrospective Cohort Study, Level III.

Greater risk of all-cause revisions and complications for obese patients in 3 106 381 total knee arthroplasties: a meta-analysis and systematic review

BACKGROUND

Obesity is a major public health issue and has considerable implications on outcomes of total knee arthroplasty (TKA). However, there has been conflicting evidence and conclusions on the effects of obesity on TKA. This meta-analysis compares the outcomes, complications, and peri-operative parameters of TKA in the obese (body mass index [BMI] ≥ 30 kg/m² ) versus non-obese (BMI < 30 kg/m² ) population as well as subgroup analysis of morbidly obese (BMI ≥ 40 kg/m² ) versus non-obese population.

METHODS

A meta-analysis was conducted with a multi-database search according to PRISMA guidelines on 12 September 2019. Data from all published literature meeting inclusion criteria were extracted and analysed.

RESULTS

Ninety-one studies were included, consisting of 917 447 obese and 2 188 834 non-obese TKA. Obese patients had higher risk of all-cause revisions (odds ratio [OR] = 1.15, 95% CI: 1.08-1.24, p < 0.0001), all complications (OR = 1.21, 95% CI: 1.06-1.38, p = 0.004), deep infections (OR = 1.47, 95% CI: 1.27-1.69, p < 0.0001), superficial infections (OR = 1.59, 95% CI: 1.32-1.91, p < 0.0001), wound dehiscence (OR = 1.46, 95% CI: 1.24-1.72, p < 0.0001) and readmissions (OR = 1.21, 95% CI: 1.05-1.40, p = 0.009). Subgroup analysis of morbidly obese patients revealed greater risks of all-cause revisions (OR = 1.25, 95% CI: 1.10-1.43, p = 0.0009), deep infections (OR = 1.98, 95% CI: 1.05-3.75, p = 0.04), superficial infections (OR = 2.44, 95% CI: 2.08-2.88, p < 0.0001) and readmissions (OR = 1.33, 95% CI: 1.20-1.47, p < 0.0001). No analysis was performed on patient reported outcome measures due to heterogeneous reporting methods.

CONCLUSION

Obese and morbidly obese patients have higher risks of revisions and infections post TKA. Surgeons should counsel patients of these risks during the informed consenting process and adopt preventative strategies into clinical practice to reduce risks where possible. In conclusion, obesity is a significant, modifiable risk factor for increased complications following TKA.

The Changing Characteristics of Arthroplasty Patients: A Retrospective Cohort Study

BACKGROUND

Total joint arthroplasty (TJA) is among the most common operations performed worldwide, with global volumes on the rise. It is important to understand if the characteristics of this patient population are changing over time for resource allocation and surgical planning. The purpose of this study is to examine how this patient population has changed between 2003 and 2017.

METHODS

A retrospective review of a prospective TJA database was conducted. Age, gender, body mass index, comorbidities, American Society of Anesthesiologists class, responsible diagnoses, and comorbidities were compared over 5-year intervals between 2003 and 2017. All patients undergoing primary, elective TJA were included.

RESULTS

Overall, 17,138 TJAs were included. Mean body mass index increased over the study period for total hip arthroplasty (THA; 29.4-30.4 kg/m², P < .0001) and total knee arthroplasty (TKA; 32.0-3.1 kg/m², P < .0001) patients. THA patients were significantly younger in more recent years (68.0-66.8 years old, P = .0026); this trend was not observed among TKA patients. Over the study period, a significantly higher proportion of patients were American Society of Anesthesiologists class III/IV for THA (50.5%-72.3%) and TKA (57.5%-80.7%) (P < .00001). Prevalence of common comorbidities did not change significantly.

CONCLUSION

The key findings of this retrospective analysis of a large prospective database are that patients undergoing TJA are becoming younger and more obese. It is unclear whether patients are becoming more medically complex. These trends paint a concerning picture of a population that is increasingly complex, and may require a greater allocation of resources in the future.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Preoperative risk stratification minimizes 90-day complications in morbidly obese patients undergoing primary total knee arthroplasty

AIMS

It has been shown that the preoperative modification of risk factors associated with obesity may reduce complications after total knee arthroplasty (TKA). However, the optimal method of doing so remains unclear. The aim of this study was to investigate whether a preoperative Risk Stratification Tool (RST) devised in our institution could reduce unexpected intensive care unit (ICU) transfers and 90-day emergency department (ED) visits, readmissions, and reoperations after TKA in obese patients.

METHODS

We retrospectively reviewed 1,614 consecutive patients undergoing primary unilateral TKA. Their mean age was 65.1 years (17.9 to 87.7) and the mean BMI was 34.2 kg/m² (SD 7.7). All patients underwent perioperative optimization and monitoring using the RST, which is a validated calculation tool that provides a recommendation for postoperative ICU care or increased nursing support. Patients were divided into three groups: non-obese (BMI < 30 kg/m², n = 512); obese (BMI 30 kg/m² to 39.9 kg/m², n = 748); and morbidly obese (BMI > 40 kg/m², n = 354). Logistic regression analysis was used to evaluate the outcomes among the groups adjusted for age, sex, smoking, and diabetes.

RESULTS

Obese patients had a significantly increased rate of discharge to a rehabilitation facility compared with non-obese patients (38.7% (426/1,102) vs 26.0% (133/512), respectively; p < 0.001). When stratified by BMI, discharge to a rehabilitation facility remained significantly higher compared with non-obese (26.0% (133)) in both obese (34.2% (256), odds ratio (OR) 1.6) and morbidly obese (48.0% (170), OR 3.1) patients (p < 0.001). However, there was no significant difference in unexpected ICU transfer (0.4% (two) non-obese vs 0.9% (seven) obese (OR 2.5) vs 1.7% (six) morbidly obese (OR 5.4); p = 0.054), visits to the ED (8.6% (44) vs 10.3% (77) (OR 1.3) vs 10.5% (37) (OR 1.2); p = 0.379), readmissions (4.5% (23) vs 4.0% (30) (OR 1.0) vs 5.1% (18) (OR 1.4); p = 0.322), or reoperations (2.5% (13) vs 3.3% (25) (OR 1.2) vs 3.1% (11) (OR 0.9); p = 0.939).

CONCLUSION

With the use of a preoperative RST, morbidly obese patients had similar rates of short-term postoperative adverse outcomes after primary TKA as non-obese patients. This supports the assertion that morbidly obese patients can safely undergo TKA with appropriate perioperative optimization and monitoring. Cite this article: Bone Joint J 2021;103-B(6 Supple A):45-50.

Predictors for readmission following primary total hip and total knee arthroplasty

BACKGROUND

Readmission following total joint arthroplasty has become a closely watched metric for many hospitals in the United States due to financial penalties imposed by Centers for Medicare and Medicaid Services. The purpose of this study was to identify both preoperative and postoperative reasons for readmission within 30 days following primary total hip and total knee arthroplasty (TKA).

METHODS

Retrospective data were collected for patients who underwent elective primary total hip arthroplasty (THA; CPT code 27130) and TKA (27447) from 2008 to 2013 at our institution. The sample was separated into readmitted and nonreadmitted cohorts. Demography, comorbidities, Charlson comorbidity index (CCI), operative parameters, readmission rates, and causes of readmission were compared between the groups using univariate and multivariate regression analysis.

RESULTS

There were 42 (3.4%) and 28 (2.2%) readmissions within 30 days for THA and TKA, respectively. The most common cause of readmission within 30 days following total joint arthroplasty was infection. Trauma was the second most common reason for readmission of a THA while wound dehiscence was the second most common cause for readmission following TKA. With univariate regression, there were multiple associated factors for readmission among THA and TKA patients, including body mass index, metabolic equivalent (MET), and CCI. Multivariate regression revealed that hospital length of stay was significantly associated with 30-day readmission after THA and TKA.

CONCLUSION

Patient comorbidities and preoperative functional capacity significantly affect 30-day readmission rate following total joint arthroplasty. Adjustments for these parameters should be considered and we recommend the use of CCI and METs in risk adjustment models that use 30-day readmission as a marker for quality of patient care.

LEVEL OF EVIDENCE

Level III/Retrospective cohort study.

The relationship between obesity and primary Total Knee Replacement: A scoping review of the literature

BACKGROUND

Primary Total Knee Replacement (TKR) is one of the most commonly performed elective orthopaedic procedures globally. Many patients undergoing this type of surgery are overweight or obese. In the UK, clinical commissioning groups have imposed arbitrary Body Mass Index (BMI) thresholds for TKR surgery. Many obese patients undergoing TKR believe they will lose weight following the procedure because of increased mobility.

AIM

This paper aims to present the findings of a scoping literature review about the relationship between obesity and primary TKR and to make recommendations for clinical practice, education and policy.

METHODS

A scoping literature review investigated the impact of BMI/body weight on the need for TKR, the impact of body weight and or BMI on patient outcomes following TKR, weight loss/gain following TKR and the implications of obesity on cost of TKR.

FINDINGS

Seventy-one papers were included in the review. Seven studies reported statistically significant associations between increased BMI/obesity with the need for TKR. Thirty of the studies reported worse outcomes for obese patients compared to non-obese comparisons. Forty of the studies reported no difference between obese and non-obese participants, including some where outcomes of obese patients were better than non-obese comparisons. Eight studies reported on changes to weight before and after TKR, three of the studies reporting a higher percentage losing weight than gaining weight and four studies reporting that obese patients gained weight. The 8th study reported that morbidly obese patients largely returned to their baseline BMI postoperatively.

CONCLUSION

The findings of the review challenge the legitimacy of setting BMI thresholds to control access to TKR surgery. There is an urgent need to develop evidence based approaches to support weight loss and weight management for this group of patients. Obese patients undergoing TKR should receive specific information regarding potential additional risks of complications and poorer outcomes. There is a need for health promotion regarding the association of being overweight/obese in young adulthood and developing osteoarthritis of the knee joints requiring TKR in middle and older age.

Revision Rates and Functional Outcomes Among Severely, Morbidly, and Super-Obese Patients Following Primary Total Knee Arthroplasty: A Systematic Review and Meta-Analysis

BACKGROUND

Obesity has been associated with a greater burden of symptomatic knee osteoarthritis. There is some evidence that patients with a very high body mass index (BMI) may have a higher risk of complications and poor outcomes following total knee replacement compared with non-obese patients or obese patients with a lower BMI. We hypothesized that increasing degrees of obesity would be associated with deteriorating outcomes for patients following total knee replacement.

METHODS

We performed a comprehensive systematic review of 4 medical databases (MEDLINE, AMED, Ovid Healthstar, and Embase) from inception to August 2016. We extracted data to determine revision risk (all-cause, septic, and aseptic) and functional outcome scores (Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC], Knee Society Score, Oxford Knee Score, EuroQol-5D, and Short Form [SF]-12 Physical Component Summary) in patients with severe obesity (BMI ≥35 kg/m), morbid obesity (BMI ≥40 kg/m), and super-obesity (BMI ≥50 kg/m) in comparison with patients with a normal BMI (<25 kg/m). Meta-analysis was performed using a random effects model.

RESULTS

We screened 3,142 titles and abstracts and 454 full-text articles to identify 40 eligible studies, of which 37 were included in the meta-analysis. Compared with patients with a normal BMI, the risk ratio for an all-cause revision surgical procedure was 1.19 (95% confidence interval [CI], 1.03 to 1.37; p = 0.02) in patients with severe obesity, 1.93 (95% CI, 1.27 to 2.95; p < 0.001) in patients with morbid obesity, and 4.75 (95% CI, 2.12 to 10.66; p < 0.001) in patients with super-obesity. The risk ratio for septic revision was 1.49 (95% CI, 1.28 to 1.72; p < 0.001) in patients with severe obesity, 3.69 (95% CI, 1.90 to 7.17; p < 0.001) in patients with morbid obesity, and 4.58 (95% CI, 1.11 to 18.91; p = 0.04) in patients with super-obesity. There were no significant differences (p > 0.05) in risk of aseptic revision. Based on the Knee Society Scores reported in a single study, patients with super-obesity had outcome scores, expressed as the standardized mean difference, that were 0.52 lower (95% CI, 0.80 lower to 0.24 lower; p < 0.001) than non-obese controls; however, no difference was observed for severe or morbidly obese patients.

CONCLUSIONS

The risk of septic revision is greater in patients with severe obesity, morbid obesity, and super-obesity, with progressively higher BMI categories associated with a higher risk. However, the risk of aseptic revision was similar between all obese and non-obese patients. Functional outcome improvements are also similar, except for super-obese patients, in whom data from a single study suggested slightly lower scores. These findings may serve to better inform evidence-based clinical, research, and policy decision-making.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Readmission Rates for One Versus Two-Midnight Length of Stay for Primary Total Knee Arthroplasty: Analysis of the Michigan Arthroplasty Registry Collaborative Quality Initiative (MARCQI) Database

BACKGROUND

The length of stay (LOS) in the hospital for total knee arthroplasty (TKA) has been declining over recent decades. The purpose of this study was to determine if patients with an LOS for TKA that includes only 1 midnight have an increased odds of 90-day readmission compared with those with a 2-midnight LOS. We also sought to identify any predictors of 90-day hospital readmission among those readmitted during our period of analysis.

METHODS

A retrospective review of the Michigan Arthroplasty Registry Collaborative Quality Initiative (MARCQI) database was performed to identify patients with a 1-midnight or 2-midnight LOS for TKA during a 5-year period. The primary end point of this study was inpatient readmission within the 90-day postoperative period. A multiple logistic regression model and propensity score matching were used to compare the odds of 90-day readmission between 1-midnight and 2-midnight LOS. The secondary end points of this study were 90-day complications.

RESULTS

There were 96,250 TKA procedures identified in the database, and 46,709 met our inclusion criteria for LOS. No difference in 90-day-readmission odds between patients with a 1-midnight LOS and those with a 2-midnight LOS for primary TKA was identified. Male sex, single marital status, age of ≥80 years, type-I diabetes, previous smoking, narcotic use prior to surgery, and a higher American Society of Anesthesiologists (ASA) scores increased the odds of 90-day readmission. Patients in the age group of ≥50 to <65 years, those with a higher preoperative hemoglobin level, and those with a positive social history of alcohol use were found to have decreased odds of readmission.

CONCLUSIONS

We found no association between the LOS for primary TKA (1 midnight compared with 2 midnights) and the 90-day readmission risk.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

What are the patient factors that impact on decisions to progress to total knee replacement? A qualitative study involving patients with knee osteoarthritis

OBJECTIVES

General practitioners (GPs) are often the first health professionals to assess patients with osteoarthritis (OA). Despite clinical guideline recommendations for non-surgical intervention as first-line therapies, the most frequent referral from a GP for a person with knee OA is to an orthopaedic surgeon. The aim of our study was to explore patient factors that impact on the decision to progress to total knee replacement (TKR), including the experience of patients in general practice, their perceptions of their condition, and their access and use of community-based allied health interventions.

DESIGN

Qualitative investigation using semi-structured interviews. The Candidacy framework was selected as a lens to examine the factors driving healthcare access. Data were analysed using a thematic analysis approach. Codes identified in the data were mapped to the seven Candidacy domains. Themes corresponding to each domain were described.

SETTING

A public hospital in Melbourne, Australia.

PARTICIPANTS

27 patients with knee OA who were on a waiting list to undergo TKR.

RESULTS

Ten themes described factors influencing access and use of non-surgical interventions and decision-making for undergoing TKR: (1) History of knee problems, change in symptoms; (2) Physical and psychosocial functioning (Identification of Candidacy); (3) GP and social networks as information sources, access to care (Navigation); (4) Referral pathways (Permeability of services); (5) Communication of impact (Appearances at health services); (6) GP-Surgeon as the predominant referral pathway (Adjudications); (7) Physical activity as painful; (8) Beliefs about effectiveness of non-surgical interventions (Offers and resistance); (9) Familiarity with local system; and (10) Availability (Operating conditions and local production of Candidacy).

CONCLUSIONS

Using the Candidacy framework to analyse patients' experiences when deciding to progress to TKR highlighted missed opportunities in general practice to orient patients to first try non-surgical interventions. Patients with knee OA also require improved support to navigate allied health services.

Variation in rehabilitation setting after uncomplicated total knee or hip arthroplasty: a call for evidence-based guidelines

Background

High-level evidence consistently indicates that resource-intensive facility-based rehabilitation does not provide better recovery compared to home programs for uncomplicated knee or hip arthroplasty patients and, therefore, could be reserved for those most impaired. This study aimed to determine if rehabilitation setting aligns with evidence regardless of insurance status.

Methods

Sub-study within a national, prospective study involving 19 Australian high-volume public and private arthroplasty centres. Individuals undergoing primary arthroplasty for osteoarthritis participated. The main outcome was the proportion participating in each rehabilitation setting, obtained via chart review and participant telephone follow-up at 35 and 90 days post-surgery, categorised as ‘facility-based’ (inpatient rehabilitation and/or ≥ four outpatient-based sessions, including day-hospital) or ‘home-based’ (domiciliary, monitored or unmonitored home program only). We compared characteristics of the study cohort and rehabilitation setting by insurance status (public or private) using parametric and non-parametric tests, analysing the knee and hip cohorts separately.

Results

After excluding ineligible participants (bilateral surgeries, self-funded insurance, participation in a concurrent rehabilitation trial, experience of a major acute complication potentially affecting their rehabilitation pathway), 1334 eligible participants remained. Complete data were available for 1302 (97%) [Knee: n = 610, mean age 68.7 (8.5) yr., 51.1% female; Hip: n = 692, mean age 65.5 (10.4) yr., 48.9% female]; 26% (158/610) of knee and 61% (423/692) of hip participants participated predominantly in home-based programs. A greater proportion of public recipients were obese and had greater pre-operative joint impairment, but participated more commonly in home programs [(Knee: 32.9% (79/240) vs 21.4% (79/370) (P = 0.001); Hip: 71.0% (176/248) vs 55.6% (247/444) (P <  0.001)], less commonly in inpatient rehabilitation [Knee: 7.5% (18/240) vs 56.0% (207/370) P (< 0.001); Hip: 4.4% (11/248) vs 33.1% (147/444) (P <  0.001], and had fewer outpatient treatments [Knee: median (IQR) 6 (3) vs 8 (6) (P < 0.001); Hip: 6 (4) vs 8 (6) (P < 0.001)].

Conclusions

Facility-based programs remain the norm for most knee and many hip arthroplasty recipients with insurance status being a major determinant of care. Development and implementation of evidence-based guidelines may help resolve the evidence-practice gap, addressing unwarranted practice variation across the insurance sectors.

Electronic supplementary material

The online version of this article (10.1186/s12891-019-2570-8) contains supplementary material, which is available to authorized users.

The projected burden of primary total knee and hip replacement for osteoarthritis in Australia to the year 2030

Background

Comprehensive national joint replacement registries with well-validated data offer unique opportunities for examining the potential future burden of hip and knee osteoarthritis (OA) at a population level. This study aimed to forecast the burden of primary total knee (TKR) and hip replacements (THR) performed for OA in Australia to the year 2030, and to model the impact of contrasting obesity scenarios on TKR burden.

Methods

De-identified TKR and THR data for 2003–2013 were obtained from the Australian Orthopaedic Association National Joint Replacement Registry. Population projections and obesity trends were obtained from the Australian Bureau of Statistics, with public and private hospital costs sourced from the National Hospital Cost Data Collection. Procedure rates were projected according to two scenarios: (1) constant rate of surgery from 2013 onwards; and (2) continued growth in surgery rates based on 2003–2013 growth. Sensitivity analyses were used to estimate future TKR burden if: (1) obesity rates continued to increase linearly; or (2) 1–5% of the overweight or obese population attained a normal body mass index.

Results

Based on recent growth, the incidence of TKR and THR for OA is estimated to rise by 276% and 208%, respectively, by 2030. The total cost to the healthcare system would be $AUD5.32 billion, of which $AUD3.54 billion relates to the private sector. Projected growth in obesity rates would result in 24,707 additional TKRs totalling $AUD521 million. A population-level reduction in obesity could result in up to 8062 fewer procedures and cost savings of up to $AUD170 million.

Conclusions

If surgery trends for OA continue, Australia faces an unsustainable joint replacement burden by 2030, with significant healthcare budget and health workforce implications. Strategies to reduce national obesity could produce important TKR savings.

Electronic supplementary material

The online version of this article (10.1186/s12891-019-2411-9) contains supplementary material, which is available to authorized users.

The AAHKS Clinical Research Award: Intraosseous Regional Prophylaxis Provides Higher Tissue Concentrations in High BMI Patients in Total Knee Arthroplasty: A Randomized Trial

BACKGROUND

Obesity is an established risk factor for periprosthetic joint infections after total knee arthroplasty (TKA). In obese patients, a larger dose of prophylactic vancomycin based on actual body weight is required to reach therapeutic concentrations. It is unclear how tissue concentrations are affected when intraosseous regional administration (IORA) is used in this population. This study compared tissue concentrations of low-dose vancomycin via IORA vs actual body weight-adjusted systemic intravenous (IV) dose in primary TKA.

METHODS

Twenty-two patients with a body mass index (BMI) >35 undergoing TKA were randomized into 2 groups. The IV group received 15 mg/kg (maximum of 2 g) of systemic IV vancomycin and the IORA group received 500 mg vancomycin into the tibia. Subcutaneous fat and bone samples were taken at regular intervals. Tissue antibiotic concentrations were measured using liquid chromatography coupled with tandem mass spectrometry. A blood sample was taken 1 to 2 hours after tourniquet deflation to measure systemic concentration.

RESULTS

The mean BMI was 41.1 in the IORA group and 40.1 in the IV systemic group. The overall mean tissue concentration in subcutaneous fat was 39.3 μg/g in the IORA group and 4.4 μg/g in the IV systemic group (P < .01). Mean tissue concentrations in bones were 34.4 μg/g in the IORA group and 6.1 μg/g in the IV systemic group (P < .01).

CONCLUSION

Low-dose IORA was effective in the high-BMI population group, providing tissue concentrations of vancomycin 5-9 times higher than systemic administration. IORA optimizes timing of vancomycin administration and provides high tissue antibiotic concentrations during TKA in this high-risk patient group.

The Effect of Obesity in Shoulder Arthroplasty Outcomes and Complications

The effect of obesity in shoulder arthroplasty has been recently reported in the literature with different and conflicting results. This review analyzes the role of obesity on outcomes and complications in shoulder arthroplasty. Morbid obesity (body mass index >40 kg/m²), more than standard obesity, is associated with a longer operative time, higher complication rate, reoperation rate and superficial infection. Obesity does not have a detrimental effect on functional outcomes. The magnitude of functional improvement in obese patients, however, can be inferior to that in nonobese patients. Obesity and morbid obesity do not increase hospital charges.

Body Mass Index Is Associated With All-cause Mortality After THA and TKA

BACKGROUND

Both obesity and underweight are associated with a higher risk of mortality in adulthood, but the association between mortality after arthroplasty and extreme ranges of body mass index (BMI) have not been evaluated beyond the first year.

QUESTIONS/PURPOSES

The purpose of this study was to investigate the association between BMI and all-cause mortality after TKA and THA.

METHODS

Data from two arthroplasty registries, the St Vincent's Melbourne Arthroplasty (SMART) Registry from Australia and the Kaiser Permanente Total Joint Replacement Registry (KPTJRR) from the United States, were used to identify patients aged ≥ 18 years undergoing elective TKAs and THAs between January 1, 2002, and December 31, 2013. Same-day bilateral THA and hemiarthroplasties were excluded. All-cause mortality was recorded from the day of surgery to the end of the study (December 31, 2013). Data capture was complete for the SMART Registry. No patients were lost to followup in the KPTJRR cohort and 2959 (5%) THAs and 5251 (5%) TKAs had missing data. Cox proportional hazard regression was used to estimate the all-cause mortality associated with six BMI categories: underweight (< 18.5 kg/m), normal weight (18.5-24.9 kg/m), overweight (25.0-29.9 kg/m), obese class I (30.0-34.9 kg/m), obese class II (35.0-39.9 kg/m), and obese class III (> 40 kg/m). For TKA, the SMART cohort had a median followup of 5 years (range, 0-12 years) and the KPTJRR cohort had a median followup of 4 years (range, 0-12 years). For THA, the SMART cohort had a median followup of 5 years (range, 0-12 years) and the KPTJRR cohort had a median followup of 4 years (range, 0-12 years).

RESULTS

In both the Australian and US cohorts, being underweight (Australia: hazard ratio [HR], 3.72; 95% confidence interval [CI], 1.94-7.08; p < 0.001 and United States: HR, 1.88; 95% CI, 1.33-2.64; p < 0.001) was associated with higher all-cause mortality after TKA, whereas obese class I (Australia: HR, 0.66; 95% CI, 0.47-0.92; p = 0.015; United States: HR, 0.71; 95% CI, 0.66-0.78; p < 0.001) or obese class II (Australia: HR, 0.54; 95% CI, 0.35-0.82; p = 0.004; United States: HR, 0.73; 95% CI, 0.66-0.81; p < 0.001) was associated with lower mortality when compared with normal-weight patients. In the US cohort, being overweight was also associated with a lower risk of mortality (HR, 0.76; 95% CI, 0.71-0.82; p < 0.001). In the US cohort, being underweight had a higher risk of mortality after THA (HR, 2.09; 95% CI, 1.65-2.64; p < 0.001), whereas those overweight (HR, 0.73; 95% CI, 0.67-0.80; p < 0.001), obese class I (HR, 0.68; 95% CI, 0.62-0.75; p < 0.001), or obese class II (HR, 0.71; 95% CI, 0.62-0.81; p < 0.001) were at a lower risk of mortality after THA when compared with normal-weight patients. In patients undergoing THA in the Australian cohort, we observed no association between BMI and risk of death.

CONCLUSIONS

We found that even severe obesity is not associated with a higher risk of death after arthroplasty. Patients should be informed of this when considering surgery. Clinicians should be cautious when considering total joint arthroplasty in underweight patients without first considering their nutritional status.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Participation in Regular Physical Activity After Total Knee or Hip Arthroplasty for Osteoarthritis: Prevalence, Associated Factors, and Type

OBJECTIVE

To describe the rates of participation in regular physical activity presurgery and at 3 years follow-up after knee or hip arthroplasty, and to describe factors associated with participation postsurgery and types of activity undertaken.

METHODS

A previously acquired multicenter, prospective cohort of knee or hip arthroplasty recipients was followed up for 3 years postsurgery. Regular participation in physical activity was defined as participation in physical activity ≥1 time/week, excluding incidental activities. Participants were interviewed about current participation as well as participation in the year presurgery. Joint-specific and health-related quality-of-life scores and information on experience of major complications were obtained. Information about comorbidity and body weight were updated. Factors associated with 3-year physical activity participation were determined using multivariable logistic regression modeling.

RESULTS

In total, 73.4% of the eligible cohort (1,289 of 1,757) were followed up (718 patients with total knee arthroplasty, and 571 patients with total hip arthroplasty). Participation profiles were similar regardless of the joint replaced. Participation in physical activity increased postsurgery in the combined cohort (from 45.2% to 63.5%; P < 0.001). Participation at 3 years was associated with participation presurgery (P < 0.0001), better 3-year quality of life (P < 0.001), younger age (P = 0.002), better 3-year joint scores (P = 0.01), >1 lifetime arthroplasty (P = 0.02), and higher education level (P = 0.04). Low-impact and nonambulatory activities significantly increased postsurgery with no change in high-impact activities.

CONCLUSION

Participation rates increased postsurgery when recovery was stable, but approximately one-third of arthroplasty recipients did not engage in physical activity at least once per week. Because participation is associated with habitual activity presurgery, a potential role for behavior change interventions is suggested. The increase in nonambulatory activities indicates that current devices measuring ambulatory activity alone are inadequate for capturing physical activity.

All-Cause Versus Complication-Specific Readmission Following Total Knee Arthroplasty

BACKGROUND

Unplanned readmissions have become an important quality indicator, particularly for reimbursement; thus, accurate assessment of readmission frequency and risk factors for readmission is critical. The purpose of this study was to determine (1) the frequency of and (2) risk factors for readmissions for all causes or procedure-specific complications within 30 days after total knee arthroplasty (TKA) as well as (3) the association between hospital volume and readmission rate.

METHODS

The Statewide Planning and Research Cooperative System (SPARCS) database from the New York State Department of Health was used to identify 377,705 patients who had undergone primary TKA in the period from 1997 to 2014. Preoperative diagnoses, comorbidities, and postoperative complications were determined using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes. Readmission was defined as all-cause, due to complications considered by the Centers for Medicare & Medicaid Services (CMS) to be TKA-specific, or due to an expanded list of TKA-specific complications based on expert opinion. Multivariable logistic regression analysis was utilized to determine the independent predictors of readmission within 30 days after surgery.

RESULTS

There were 22,076 all-cause readmissions-a rate of 5.8%, with a median rate of 3.9% (interquartile range [Q1, Q3] = 1.1%, 7.2%]) among the hospitals-within 30 days after discharge. Of these, only 11% (0.7% of all TKAs) were due to complications considered to be TKA-related by the CMS whereas 31% (1.8% of all TKAs) were due to TKA-specific complications on the expanded list based on expert opinion. Risk factors for TKA-specific readmissions based on the expanded list of criteria included an age of >85 years (odds ratio [OR] = 1.32, 95% confidence interval [CI] = 1.15 to 1.52), male sex (OR = 1.41, 95% CI = 1.34 to 1.49), black race (OR = 1.24, 95% CI = 1.14 to 1.34), Medicaid coverage (OR = 1.40, 95% CI = 1.26 to 1.57), and comorbidities. Several comorbid conditions contributed to the all-cause but not the TKA-specific readmission risk. Very low hospital volume (<90 cases per year) was associated with a higher readmission risk.

CONCLUSIONS

The frequency of readmissions for TKA-specific complications was low relative to the frequency of all-cause readmissions. Reasons for hospital readmission are multifactorial and may not be amenable to simple interventions. Health-care-quality measurement of readmission rates should be calculated and risk-adjusted on the basis of procedure-specific criteria.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Predicting the Long-Term Gains in Health-Related Quality of Life After Total Knee Arthroplasty

BACKGROUND

We investigated the predictors of long-term gains in quality-adjusted life years (QALYs) from total knee arthroplasty (TKA) and the patient attributes that predicted cost-effective TKA.

METHODS

Data on TKA patients (n = 570) from 2006 to 2007 were extracted from a single-institution registry. QALY gains over 7 years post surgery were calculated from health-related quality of life (HrQoL) scores measured preoperatively and annually postoperatively using the short-form health survey (SF-12) instrument. Multivariate linear regression analysis investigated the predictors of QALY gain from TKA from a broad range of preoperative patient characteristics and was used to predict QALY gains for each individual. Patients were grouped into deciles according to their predicted QALY gain, and the cost-effectiveness of each decile was plotted on the cost-effectiveness plane. Patient attribute differences between deciles were decomposed.

RESULTS

After exclusions and dropout, data were available for 488 patients. The average estimated QALY gain over 7 years was 0.77 (95% confidence interval [CI] 0.70-0.83). Predictors significantly associated with smaller QALY gains were comorbidities (Charlson comorbidity index 3+ coefficient -0.54 CI -0.15 to -0.92), the absence of severe osteoarthritis in the ipsilateral knee (-0.51 CI -0.16 to -0.85), preoperative HrQoL (standardized coefficient -0.34 CI -0.26 to -0.43), the requirement for an interpreter (-0.24 CI -0.05 to -0.44), and age (-0.01 CI -0.01 to -0.02). The largest difference between cost-effective and non-cost-effective deciles was relatively high preoperative HrQoL in the non-cost-effective decile.

CONCLUSION

TKA is likely to be cost-effective for most patients except those with unusually high preoperative HrQoL or a lack of severe osteoarthritis. The poorer outcomes for those requiring an interpreter requires further research.

Obesity and the Relative Risk of Knee Replacement Surgery in Patients With Knee Osteoarthritis: A Prospective Cohort Study

OBJECTIVE

It is unclear what impact obesity has on the progression of knee osteoarthritis (OA) from diagnosis to knee replacement surgery. This study was undertaken to examine the relative risk of knee replacement surgery in overweight and obese patients who were newly diagnosed as having knee OA in a community setting.

METHODS

Subjects were selected from the Information System for Development of Primary Care Research database, which compiles comprehensive clinical information collected by health care professionals for >5.5 million people in Catalonia, Spain (80% of the population). Patients newly diagnosed as having knee OA in primary care between 2006 and 2011 were included. Knee replacement was ascertained using International Classification of Diseases, Ninth Revision, Clinical Modification codes from linked hospital admissions data. Multivariable Cox regression models were fitted for knee replacement according to body mass index (BMI), and were adjusted for relevant confounders. Population proportional attributable risk was calculated.

RESULTS

A total of 105,189 participants were followed up for a median of 2.6 years (interquartile range 1.3-4.2). Of these patients, 7,512 (7.1%) underwent knee replacement. Adjusted hazard ratios and 95% confidence intervals (95% CIs) for knee replacement for the World Health Organization BMI categories were 1.41 (95% CI 1.27-1.57) for overweight, 1.97 (95% CI 1.78-2.18) for obese I, 2.39 (95% CI 2.15-2.67) for obese II, and 2.67 (95% CI 2.34-3.04) for obese III compared to normal weight. The effect of BMI on risk of knee replacement was stronger among younger participants. The population attributable risk of obesity for knee OA-related knee replacement was 31.0%.

CONCLUSION

Overweight and obese patients are at >40% and 100% increased risk of knee replacement surgery, respectively, compared to patients with normal weight. This association is even stronger in younger patients. Weight reduction strategies could potentially reduce the need for knee replacement surgery by 31% among patients with knee OA.

Outcomes of primary reverse shoulder arthroplasty in patients with morbid obesity

BACKGROUND

Obesity is a risk factor for worse outcomes in anatomic shoulder arthroplasty. The purpose of this investigation was to determine outcomes of primary reverse shoulder arthroplasty (RSA) in patients with morbid obesity.

METHODS

We reviewed all primary RSAs performed on morbidly obese (body mass index [BMI] ≥40 kg/m(2)) patients from 2005 to 2012 at our institution with at least 2 years of follow-up. The study included 41 patients (57% female), the mean BMI was 44 kg/m(2), and the mean age was 67.7 years.

RESULTS

The only intraoperative complication was an inferior glenoid fracture that remained stable after glenosphere implantation. At a mean follow-up of 3.2 years (range 2-7.36 years), 2 patients (5%) required revision surgery for infection (n = 1) and humeral loosening (n = 1). Survival was 98% at 2 years and 92% at 5 years. Additional postoperative complications included ulnar neuropathy (n = 1) and heterotopic ossification (n = 2). Pain relief was excellent, with 93% reporting moderate or severe pain preoperatively compared with 2% postoperatively (P < .001). Shoulder abduction improved from 49° to 142° and external rotation from 17° to 50° (P < .001). The average American Shoulder and Elbow Surgeons score was 71.1. At the most recent follow-up, no patients had glenoid lucency, 1 (2%) had humeral lucency, and 2 (5%) had inferior scapular notching. Laborers had higher risk for revision surgery (P = .01), and females had worse functional outcomes and shoulder motion (P < .02).

CONCLUSIONS

RSA is a successful procedure in morbidly obese patients (BMI ≥40 kg/m(2)). At intermediate follow-up, there is good implant survival with a reasonable complication rate and excellent pain relief.

Addressing obesity in the management of knee and hip osteoarthritis - weighing in from an economic perspective

Background

Obesity is one of the only modifiable risk factors for both incidence and progression of Osteoarthritis (OA). So there is increasing interest from a public health perspective in addressing obesity in the management of OA. While evidence of the efficacy of intereventions designed to address obesity in OA populations continues to grow, little is known about their economic credentials.

The aim of this study is to conduct a scoping review of: (i) the published economic evidence assessing the economic impact of obesity in OA populations; (ii) economic evaluations of interventions designed to explicitly address obesity in the prevention and management of OA in order to determine which represent value for money. Besides describing the current state of the literature, the study highlights research gaps and identifies future research priorities.

Methods

In July 2014, a search of the peer reviewed literature, published in English, was undertaken for the period January 1975 – July 2014 using Medline Complete (Ebscohost), Embase, Econlit, Global Health, Health Economics Evaluation Database (HEED), all Cochrane Library databases as well as the grey literature using Google and reference lists of relevant studies. A combination of key search terms was used to identify papers assessing the economic impact of obesity in OA or economic evaluations conducted to assess the efficiency of obesity interventions for the prevention or management of OA.

Results

14 studes were identified; 13 were cost burden studies assessing the impact of obesity as a predictor for higher costs in Total Joint Arthroplasty (TJA) patients and one a cost-effectiveness study of an intervention designed to address obesity in the managment of mild to moderate OA patients.

Conclusion

The majority of the economic studies conducted are cost burden studies. While there is some evidence of the association between severe obesity and excess hospital costs for TJA patients, heterogeneity in studies precludes definitive statements about the strength of the association. With only one economic evaluation to inform policy and practice, there is a need for future research into the cost-effectiveness of obesity interventions designed both for prevention or management of OA along the disease spectrum and over the life course.

Hip and knee arthroplasty implants contraindicated in obesity

INTRODUCTION

High patient weight is a risk factor for mechanical implant failure and some manufacturers list obesity as a contraindication for implant use. We reviewed data from the 2012-2013 UK National Joint Registry to determine whether surgical practice reflects these manufacturer recommendations.

METHODS

The product literature for the most commonly used hip and knee implants was reviewed for recommendations against use in obese patients (body mass index [BMI] ≥ 30kg/m(2)). The total number of obese patients undergoing hip and knee arthroplasty was calculated, as was the proportion receiving implants against manufacturer recommendations.

RESULTS

Out of 200,054 patient records, 147,691 (74%) had a recorded BMI. The mean BMI for patients undergoing primary total hip arthroplasty was 29kg/m(2), compared with 31kg/m(2) for total knee arthroplasty. Of the 25 components reviewed, 5 listed obesity as a contraindication or recommended against implant use in obese patients. A total of 10,745 patients (16% of all obese patients) received implants against manufacturer recommendations.

CONCLUSIONS

A high proportion of patients are receiving implants against manufacturer recommendations. However, there are limitations to using BMI for stratifying risk of implant fatigue failure and manufacturers should therefore provide more detailed guidelines on size specific implant load limits to facilitate surgical decisions.

Cost-effectiveness of Crohn’s disease post-operative care

AIM: To define the cost-effectiveness of strategies, including endoscopy and immunosuppression, to prevent endoscopic recurrence of Crohn’s disease following intestinal resection.

METHODS: In the “POCER” study patients undergoing intestinal resection were treated with post-operative drug therapy. Two thirds were randomized to active care (6 mo colonoscopy and drug intensification for endoscopic recurrence) and one third to drug therapy without early endoscopy. Colonoscopy at 18 mo and faecal calprotectin (FC) measurement were used to assess disease recurrence. Administrative data, chart review and patient questionnaires were collected prospectively over 18 mo.

RESULTS: Sixty patients (active care n = 43, standard care n = 17) were included from one health service. Median total health care cost was $6440 per patient. Active care cost $4824 more than standard care over 18 mo. Medication accounted for 78% of total cost, of which 90% was for adalimumab. Median health care cost was higher for those with endoscopic recurrence compared to those in remission [$26347 (IQR 25045-27485) vs $2729 (IQR 1182-5215), P < 0.001]. FC to select patients for colonoscopy could reduce cost by $1010 per patient over 18 mo. Active care was associated with 18% decreased endoscopic recurrence, costing $861 for each recurrence prevented.

CONCLUSION: Post-operative management strategies are associated with high cost, primarily medication related. Calprotectin use reduces costs. The long term cost-benefit of these strategies remains to be evaluated.

Do women have poorer outcomes following total knee replacement?

OBJECTIVE

To investigate whether women have poorer pain and functional outcomes following total knee replacement (TKR) and to investigate factors that may contribute to this poorer outcome.

METHODS

In a cohort of 494 people, outcomes were the Pain and Function/Daily Activity subscales of the Knee Injury and Osteoarthritis Outcome Score (KOOS) at 6 and 12 months post-surgery. Sequential multivariable regression analyses evaluated the following independent variables: (1) sex; (2) sex and age; (3) sex, age and pre-surgery score for respective outcome measures; and, (4) model 3 and body mass index (BMI), education, low back pain (LBP), depression, comorbidities, and symptomatic joint count.

RESULTS

The sample included 323 women and 171 men. Women were significantly worse on several factors pre-surgery: pain: 39.0 vs 44.9, P = 0.002; function: 47.7 vs 55.0, P < 0.0001; depression 5.6 vs 4.7, P = 0.006; obesity (BMI ≥30): 54.2 vs 36.3%, P = 0.0002; and, symptomatic joint count: ≥4: 61.3 vs 44.4%, P = 0.002. Women had worse outcomes for pain (72.2 vs 76.1, P = 0.04) and function (75.2 vs 80.5, P = 0.007) at 6 months. This effect was attenuated by adding pre-surgery pain/function. However, the magnitude of the association of pre-surgery pain/function was reduced when LBP, depression, BMI, education level, joint count and comorbidity count were added suggesting association with pre-surgery pain and function. Twelve month results were similar.

CONCLUSION

Women appear to have worse outcomes than men possibly due to a putative pre-operative profile across many factors. Consideration of TKR when impairments in pain and function are less severe along with interventions that address mood and comorbidity may improve outcomes for women having TKR.

Complications of Morbid Obesity in Total Joint Arthroplasty: Risk Stratification Based on BMI

This study stratifies complication risk in primary total joint arthroplasty (TJA) based on body mass index (BMI). Demographics, co-morbidities, perioperative variables, and complications were reviewed for 22,808 patients. Chi-squared, one-way ANOVA, univariate and multivariable regression analysis were performed. Increasing BMI led to an increase (P<0.05) in combined complications, acute kidney injury (AKI), cardiac arrest (CA), reintubation, reoperation, and superficial infection (SI). Univariate analysis for BMI>40 revealed an increase in combined complications (15.21-vs-17.40%), AKI (1.93-vs-3.87%), CA (0.22-vs-0.57%), reintubation (0.47-vs-0.95%), reoperation (2.36-vs-3.37%), and SI (0.82-vs-1.65%). Multivariable regression showed BMI>40 as an independent predictor for combined complications (OR=1.18), AKI (OR=1.79), CA (OR=3.94), reintubation (OR=2.56), reoperation (OR=1.44), and SI (OR=2.11). Morbid obesity confers increased risk for complications in TJA.

Two-Day Length of Stay is Not Inferior to 3 Days in Total Knee Arthroplasty with Regards to 30-Day Readmissions

The impact of a shortened length of stay (LOS) following total knee arthroplasty (TKA) on the risk of readmission is not well documented despite recent trends towards shorter hospitalization. We retrospectively compared the adjusted risk of 30-day readmission following TKA between patients with 2-, 3- and 4-day LOS using current postoperative care protocols. A total of 23,655 consecutive primary, unilateral TKAs operated between 01/01/2009 and 12/31/2011 were studied retrospectively using non-inferiority testing. The main outcome was 30-day readmission. Two-day LOS decreased the odds of readmission by a factor of 0.96, with an upper bound one-sided 95% confidence interval of 1.10. After adjusting for other variables, LOS of 2 days is not inferior to 3 days with respect to the risk of 30-day readmission.

Review article: Outcome of total knee arthroplasty in obese patients

The MEDLINE database was searched using the key words: 'obesity' and 'knee arthroplasty'. 41 articles focused on the topic were reviewed; most studies were prospective case series (providing low-level evidence) and 3 were systematic reviews. 16 studies reported no adverse association between obesity and total knee arthroplasty (TKA) outcome, whereas 24 studies reported a poorer TKA outcome in obese patients. In the 3 systematic reviews, obesity was reported to adversely affect the outcome, the rate of complications, implant survival, and the cost of TKA.

The effect of obesity and increasing age on operative time and length of stay in primary hip and knee arthroplasty

We retrospectively reviewed 589 patients undergoing lower-limb arthroplasty, recording age, body mass index (BMI) and co-morbidities. The effect of these on operative duration and length of stay (LOS) was analysed. For a 1 point increase in BMI we expect LOS to increase by a factor of 2.9% and mean theatre time to increase by 1.46minutes. For a 1-year increase in age, we expect LOS to increase by a factor of 1.2%. We have calculated the extra financial costs associated. The current reimbursement system underestimates the financial impact of BMI and age. The results have been used to produce a chart that allows prediction of LOS following lower limb arthroplasty based on BMI and age. These data are of use in planning operating lists.

Predictive risk factors for 30-day readmissions following primary total joint arthroplasty and modification of patient management

The Centers for Medicare and Medicaid have begun to publically publish statistics on readmissions following primary total hip (THA) and total knee arthroplasty (TKA). Our study retrospectively assesses 30-day readmissions rates following THA and TKA, performed by a single surgeon at a tertiary care medical center between 2007 and 2012. Results of a univariate analysis and logistic regression model indicated female gender, high ASA class, and increased operative time to be significantly associated with higher rates of readmission (OR 4.646, OR 1.257, and OR 5.323, respectively). Readmissions most often occurred within the first week of patient discharge. Surgical complications and gastrointestinal discomfort were the most common causes for readmission. Using readmission risk we can stratify patients into tiered critical care pathways to reduce readmissions.

Obesity increases operating room times in patients undergoing primary hip arthroplasty: a retrospective cohort analysis

Background. Obesity impacts utilization of healthcare resources. The goal of this study was to measure the relationship between increasing body mass index (BMI) in patients undergoing total hip arthroplasty (THA) with different components of operating room (OR) time.

Methods. The Stanford Translational Research Integrated Database Environment (STRIDE) was utilized to identify all ASA PS 2 or 3 patients who underwent primary THA at Stanford Medical Center from February 1, 2008 through January 1, 2013. Patients were divided into five groups based on the BMI weight classification. Regression analysis was used to quantify relationships between BMI and the different components of total OR time.

Results. 1,332 patients were included in the study. There were no statistically significant differences in age, gender, height, and ASA PS classification between the BMI groups. Normal-weight patients had a total OR time of 138.9 min compared 167.9 min (P < 0.001) for morbidly obese patients. At a BMI > 35 kg/m² each incremental BMI unit increase was associated with greater incremental total OR time increases.

Conclusion. Morbidly obese patients required significantly more total OR time than normal-weight patients undergoing a THA procedure. This increase in time is relevant when scheduling obese patients for surgery and has an important impact on health resource utilization.

Selecting those to refer for joint replacement: who will likely benefit and who will not?

Osteoarthritis (OA) is one of the 10 most disabling diseases in developed countries and worldwide estimates are that 10% of men and 18% of women aged over 60 years have symptomatic OA, including moderate and severe forms. Total joint replacement (TJR) is considered the most effective treatment for end-stage OA in those who have exhausted available conservative interventions. The demand for TJR is continually rising due to the ageing population; in the United States, more than 1 million TJRs were performed in 2010 and the number of procedures is projected to exceed 4 million in the US by 2030. It has been estimated that of all hip and knee replacements performed, approximately one quarter of the patients may be considered inappropriate candidates. Predicting who will benefit from TJR and who will not would seem critical in terms of containing the current and projected expenditure as well as improving satisfaction in TJR recipients. Few formal predictive tools are available to aid referring clinicians to determine those likely to be good or poor responders to surgery and current available tools tend to focus on disease severity alone with little consideration of risk factors that may predict a poor outcome or impede an effective response to surgery. This review examines the tools available to assist with assessing appropriateness for TJR; investigates the modifiable risk factors associated with poor outcome; and identifies areas for future research in selecting those appropriate for joint replacement.

Outcomes and Costs of Reverse Shoulder Arthroplasty in the Morbidly Obese: A Case Control Study

BACKGROUND

The rising number of morbidly obese patients has important consequences for the health-care system. We investigated the effect of morbid obesity on outcomes, complications, discharge disposition, and costs in patients undergoing reverse shoulder arthroplasty.

METHODS

Our joint registry was searched for all patients who had undergone primary reverse shoulder arthroplasty for a reason other than fracture from 2003 to 2010 and had a minimum of twenty-four months of follow-up. Twenty-one patients with a body mass index (BMI) of ≥40 kg/m² were identified (follow-up, 45 ± 16 months; sex, seventeen female and four male; age, 69 ± 7 years) and were compared with sixty-three matched control patients with a BMI of <30 kg/m² (follow-up, 48 ± 20 months; sex, fifty female and thirteen male; age, 71 ± 6 years) after an a priori sample size calculation. Outcome instrument data were obtained preoperatively and postoperatively. The Charlson-Deyo comorbidity index (CDI) score, total comorbidities, operative time, blood loss, duration of hospital stay, discharge disposition, costs, and complications were recorded.

RESULTS

Compared with nonobese patients, morbidly obese patients had similar improvements in functional outcomes (e.g., American Shoulder and Elbow Surgeons score, 32 to 69 compared with 40 to 78) and in shoulder motion (e.g., forward flexion, 61° to 140° compared with 74° to 153°); all improvements were significant (p < 0.05). Morbidly obese patients had a similar rate of scapular notching (odds ratio [OR] = 0.58, p = 0.63), more total comorbidities excluding obesity (six compared with four, p = 0.001), a higher CDI (2 compared with 1, p = 0.025), and a higher rate of obstructive sleep apnea (OR = 27.7, p = 0.0001). Their operative time was thirteen minutes longer (p = 0.014) and their blood loss was 40 mL greater (p = 0.008). Morbidly obese patients had a similar duration of stay (3.1 compared with 2.6 days, p = 0.823) and hospital readmission rate (OR = 16.3, p = 0.08) but a sixfold higher rate of discharge to rehabilitation facilities rather than to home (OR = 8, p < 0.0001). Hospital costs were higher by $2974 (p = 0.009). The rates of major complications (n = 4 compared with 8, p = 0.479) and of minor complications (n = 3 compared with 14, p = 0.440) were similar. No intraoperative complications or mechanical device failures were noted in either group.

CONCLUSIONS

Reverse shoulder arthroplasty appears to be as safe and effective in morbidly obese patients, although it has an increased cost and patients have a lower rate of discharge to home and greater care needs after discharge.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

The Influence of Obesity on the Outcome of TKR: Can the Impact of Obesity be justified from the Viewpoint of the Overall Health Care System?

BACKGROUND

There is controversy in the literature regarding the justification of performing total knee replacement (TKR) in obese patients in view of their increased risk of poor outcomes and how those poorer outcomes impact the health care system overall.

QUESTIONS/PURPOSES

Is TKR justifiable in the obese patient? Can the negative impact of continuing to perform TKR in the obese be quantified?

METHODS

A Cochrane Library, PubMed (MEDLINE), and Google Scholar search related to the justification of TKR in the obese patient and its impact on the health care system was analyzed. The main criteria for selection were that the articles were focused in the aforementioned questions.

RESULTS

Two thousand one hundred seventy-three articles were found, but only 50 were selected and reviewed because they were focused on the questions of this paper. Although some articles (with low grade of evidence) did not find that obesity adversely affected the outcome of TKR, most of them found that obesity adversely affected the results of TKR. Regarding complications rates and survival rates, obesity has shown to have a negative influence on outcome after TKR. The improvements in patient-reported outcome measures, however, were similar irrespective of body mass index. Regarding the impact of TKR in obese patients, an extra cost of US$3,050 has been reported per patient. Considering that 50% of the US population is obese and that 600,000 TKRs are implanted per year, the impact for the US health system could be as much as 915 million dollars (300,000 × 3,050).

CONCLUSION

TKR in obese patients may be justifiable because the functional improvements appear equivalent to those of patients with a lower BMI. However, in obese patients, the risk of complications is higher and the prosthetic survival is lower. Moreover, TKR in obese patients has a huge impact on the health system which should be considered.

The effect of obesity on direct medical costs in total knee arthroplasty

BACKGROUND

Obesity prevalence continues to rise in the United States. We sought to examine the effect of obesity on length of hospital stay and direct medical costs in a large cohort of patients who underwent total knee arthroplasty.

METHODS

The study included 8129 patients who had undergone 6475 primary total knee arthroplasties and 1654 revision total knee arthroplasties at a large U.S. medical center from January 1, 2000, to September 30, 2008. Patients with bilateral procedures within ninety days following the index admission were excluded. Data on clinical and surgical characteristics and complications were obtained from the original medical records and the institutional joint registry. Patients were classified into eight groups based on their body mass index at the time of surgery. Direct medical costs were calculated in 2010 U.S. dollars by using standardized, inflation-adjusted costs for services and procedures billed during hospitalization and the ninety-day window. Study end points were hospital length of stay and direct medical costs. End points were compared across the eight body mass index categories in both unadjusted and multivariable risk-adjusted analyses. Linear regression models were used to determine the cost impact associated with increasing body mass index and obesity accounting for comorbidities and complications.

RESULTS

Body mass index data were available for 99.5% of patients and ranged from 15 to 73 kg/m2. Length of stay and the direct medical costs were lowest for patients with body mass index values in the normal to overweight range. Increasing body mass index was associated with significantly longer hospital stays and costs. Every 5-unit increase in body mass index beyond 30 kg/m2 was associated with approximately $250 to $300 higher hospitalization costs in primary total knee arthroplasty and $600 to $650 higher hospitalization costs in revision total knee arthroplasty. These estimates persisted after adjusting for comorbidities or complications.

CONCLUSIONS

Obesity is associated with longer hospital stays and higher costs in total knee arthroplasty. The effect of obesity on costs appears to be independent of obesity-related comorbid conditions and complications.

Outcomes following large joint arthroplasty: does socio-economic status matter?

BACKGROUND

We sought to determine whether socio-economic status (SES) is an independent predictor of outcome following total knee (TKR) and hip (THR) replacement in Australians.

METHODS

In this prospective cohort study, we included patients undergoing TKR and THR in a public hospital in whom baseline and 12-month follow-up data were available. SES was determined using the Australian Bureau of Statistics 'Index of Relative Advantage and Disadvantage'. Other independent variables included patients' demographics, comorbidities and procedure-related variables. Outcome measures were the International Knee Society Score and Harris Hip Score pain and function subscales, and the Short Form Health Survey (SF-12) physical and mental component scores.

RESULTS

Among 1,016 patients undergoing TKR and 835 patients undergoing THR, in multiple regression analysis, SES score was not independently associated with pain and functional outcomes. Female sex, older age, being a non-English speaker, higher body mass index and presence of comorbidities were associated with greater post-operative pain and poorer functional outcomes following arthroplasty. Better baseline function, physical and mental health, and lower baseline level of pain were associated with better outcomes at 12 months. In univariate analysis, for TKR, the improvement in SF-12 mental health score post arthroplasty was greater in patients of lower SES (3.8 ± 12.9 versus 1.5 ± 12.2, p=0.008), with a statistically significant inverse association between SES score and post-operative SF-12 mental health score in linear regression analysis (coefficient-0.28, 95% CI: -0.52 to -0.04, p=0.02).

CONCLUSIONS

When adjustments are made for other covariates, SES is not an independent predictor of pain and functional outcome following large joint arthroplasty in Australian patients. However, relative to baseline, patients in lower socioeconomic groups are likely to have greater mental health benefits with TKR than more privileged patients. Large joint arthroplasty should be made accessible to patients of all SES.

Understanding readmission after primary total hip and knee arthroplasty: who's at risk?

Readmission has been cited as an important quality measure in the Patient Protection and Affordable Care Act. We queried an electronic database for all patients who underwent Total Hip Arthroplasty or Total Knee Arthroplasty at our institution from 2006 to 2010 and identified those readmitted within 90 days of surgery, reviewed their demographic and clinical data, and performed a multivariable logistic regression analysis to determine significant risk factors. The overall 90-day readmission rate was 7.8%. The most common readmission diagnoses were related to infection and procedure-related complications. An increased likelihood of readmission was found with coronary artery disease, diabetes, increased LOS, underweight status, obese status, age (over 80 or under 50), and Medicare. Procedure-related complications and wound complications accounted for more readmissions than any single medical complication.

Thirty-day postoperative complications and mortality following total knee arthroplasty: incidence and risk factors among a national sample of 15,321 patients

BACKGROUND

The purpose of this investigation was to determine the incidence rates of, and identify risk factors for, thirty-day postoperative mortality and complications among more than 15,000 patients who underwent a primary unilateral total knee arthroplasty as documented in the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP).

METHODS

The NSQIP database was queried to identify patients who had undergone primary unilateral total knee arthroplasty between 2006 and 2010. Patient demographics, medical history, and surgical characteristics were recorded, as were thirty-day postoperative complications, mortality, and length of hospital stay. Complications were divided into categories, which included major systemic complications (complications requiring complex medical intervention) and major local complications (including deep wound infection and peripheral nerve injury). Univariate testing and multivariate logistic regression analysis were used to identify significant independent predictors of the outcome measures.

RESULTS

A total of 15,321 individuals underwent primary unilateral total knee arthroplasty. The mean age (and standard deviation) of the patients was 67.3 ± 10.2 years. Obesity (a body mass index [BMI] of ≥30 kg/m²) was documented in 61.2% of cases, 18.2% of patients had diabetes, and 50% were graded as Class 3 or higher on the basis of the American Society of Anesthesiologists (ASA) classification system. The thirty-day mortality rate was 0.18%, and 5.6% of the patients experienced complications. Patient age (odds ratio [OR] = 1.12; 95% confidence interval [CI] = 1.06 to 1.17) and diabetes (OR = 2.99; 95% CI = 1.35 to 6.62) were independent predictors of mortality. A BMI of ≥40 kg/m² was an independent predictor of postoperative complications (OR = 1.47; 95% CI = 1.09 to 1.98). Patient age of eighty years or older, an ASA classification of ≥3, and an operative time of >135 minutes influenced the development of any postoperative complication as well as major and minor systemic complications. Cardiac disease (OR = 4.32; 95% CI = 1.01 to 18.45) and a BMI of ≥40 kg/m² (OR = 2.01; 95% CI = 1.02 to 3.97) were associated with minor local complications.

CONCLUSIONS

Patient age and diabetes increased the risk of mortality after primary total unilateral knee arthroplasty. Predictive factors impacting the development of postoperative complications included an ASA classification of ≥3, increased operative time, increased age, and greater body mass.

The cost of obesity for nonbariatric inpatient operative procedures in the United States: national cost estimates obese versus nonobese patients

OBJECTIVE

To evaluate the economic impact of obesity on hospital costs associated with the commonest nonbariatric, nonobstetrical surgical procedures.

BACKGROUND

Health care costs and obesity are both rising. Nonsurgical costs associated with obesity are well documented but surgical costs are not.

METHODS

National cost estimates were calculated from the Healthcare Cost and Utilization Project (HCUP) Nationwide Inpatient Sample (NIS) database, 2005-2009, for the highest volume nonbariatric nonobstetric procedures. Obesity was identified from the HCUP-NIS severity data file comorbidity index. Costs for obese patients were compared with those for nonobese patients. To control for medical complexity, each obese patient was matched one-to-one with a nonobese patient using age, sex, race, and 28 comorbid defined elements.

RESULTS

Of 2,309,699 procedures, 439,8129 (19%) were successfully matched into 2 medically equal groups (obese vs nonobese). Adjusted total hospital costs incurred by obese patients were 3.7% higher with a significantly (P < 0.0001) higher per capita cost of $648 (95% confidence interval [CI]: $556-$736) compared with nonobese patients. Of the 2 major components of hospital costs, length of stay was significantly increased in obese patients (mean difference = 0.0253 days, 95% CI: 0.0225-0.0282) and resource utilization determined by costs per day were greater in obese patients due to an increased number of diagnostic and therapeutic procedures needed postoperatively (odds ratio [OR] = 0.94, 95% CI: 0.93-0.96). Postoperative complications were equivalent in both groups (OR = 0.97, 95% CI: 0.93-1.02).

CONCLUSIONS

Annual national hospital expenditures for the largest volume surgical procedures is an estimated $160 million higher in obese than in a comparative group of nonobese patients.

Overweight preoperatively impairs clinical outcome after knee arthroplasty: a cohort study of 197 patients 3–5 years after surgery

BACKGROUND

Obesity contributes much to the development of knee osteoarthritis. However, the association between obesity and outcome after knee replacement is controversial. We investigated whether there was an association between the preoperative body mass index (BMI) of patients who underwent total knee arthroplasty (TKA) and their quality of life (QoL) and physical function 3-5 years after surgery.

METHODS

197 patients who had undergone primary TKA participated in a 3-5 year follow-up study. The outcome measures were the patient-reported Short Form 36 (SF-36) and the American Knee Society score (KSS).

RESULTS

Ordinal logistic regression analysis (adjusted for age, sex, disease, and surgical approach) revealed a statistically significant correlation between BMI and 9 of the 14 outcome measures. For all outcome measures, we found an odds ratio (OR) of < 1. A difference in BMI of 1 kg/m(2) increased the risk of a lower score from a minimum of 2% (OR = 0.98 (0.93-1.03); p = 0.5) (Mental Component score) to a maximum of 13% (OR = 0.87 (0.82-0.93); p < 0.001) (KSS function score).

INTERPRETATION

Our findings indicate that TKA patients' preoperative BMI is a predictor of the clinical effect and patients' quality of life 3-5 years postoperatively. A high BMI increases the risk of poor QoL (SF-36) and physical function (KSS).

Obese patients undergoing total knee arthroplasty have distinct preoperative characteristics: an institutional study of 4718 patients

Obesity affects a disproportionate proportion of total knee arthroplasty (TKA) patients. Our study explores pre-operative characteristics between obese and non-obese patients undergoing TKA surgery. A cohort of 4718 osteoarthritic patients, undergoing primary TKA, was studied. Patients were stratified according to BMI classes. Each class was compared in terms of age, race, gender, level of education, insurance status, pre-operative WOMAC, SF-36, and Elixhauser comorbidities. There was a positive relationship between BMI and female gender, non-white race, Medicaid, private insurance, and self-pay. A negative relationship was observed between BMI and age, Medicare, WOMAC and SF-36. Obese TKA candidates differ from their non-obese counterparts in a number of demographic, socioeconomic, and clinical characteristics.