Role of obesity on the risk for total hip or knee arthroplasty

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.

Modeling the impact of obesity on cost of hip and knee arthroplasty

PURPOSE

This study aimed to determine the proportions of total knee arthroplasty (TKA) and total hip arthroplasty (THA) attributable to obesity in Ireland and the associated hospital costs.

METHODS

Sex- and age-specific numbers of primary TKA and THA procedures and length of stay were estimated using Irish population data from the Central Statistics Office (sex and age) and data from the national Hospital Inpatient Enquiry (numbers of TKA and THA procedures, length of stay, diagnostic-related group codes, sex, and age). Population attributable fractions of TKA and THA related to obesity were calculated using relative risks for different weight groups obtained from published literature. Nationally representative weight and height data were available from the 2015 Healthy Ireland Survey (n = 6142) and extrapolated to the Irish population. Diagnostic-related group tariffs from the Healthcare Pricing Office were used to estimate hospital costs of TKA and THA.

RESULTS

In 2015, 2296 TKA and 3411 THA procedures were performed in public hospitals in Ireland. Of those procedures, 43% of TKA and 20% of THA were attributable to obesity. This equates to €16.0 million out of €52.1 million of TKA- and THA-related hospital costs.

CONCLUSIONS

Effective obesity control has potential to decrease the demand for joint replacements and associated costs.

How I treat obese patients with oral anticoagulants

Obesity has become a major threat to health worldwide. The prevalence of obesity is rapidly increasing, so much so that the World Health Organization has declared obesity as a global epidemic. Obesity is associated with multiple health problems, including venous thromboembolism and atrial fibrillation, both of which are treated with anticoagulation. However, obesity and treatments for obesity such as bariatric surgery can influence absorption, excretion, pharmacokinetics, and pharmacodynamics of various anticoagulants. This results in uncertainty regarding the best antithrombotic strategies in this population, particularly in the morbidly obese. In the recent years, several studies have attempted to investigate anticoagulation use in this population and provided more insight. Herein, we present 4 cases of anticoagulant use in the obese to illustrate the common challenges faced by clinicians and discuss our approach. Whenever possible, we provide a review of the literature and base our recommendations on the best available evidence.

Potential Risk Factors Contributing to Development of Venous Thromboembolism for Total Knee Replacements Patients Prophylaxed With Rivaroxaban: A Retrospective Case-Control Study

Rivaroxaban after total knee arthroplasty (TKA) is used to prevent postoperative venous thromboembolism (VTE); however, despite thromboprophylaxis, some patients still develop postoperative VTE. To determine whether tourniquet time, time to initiate rivaroxaban (TTI_RIV), or Body Mass Index (BMI) was associated with postoperative VTE. A retrospective case-control study was conducted. Those patients that developed VTE despite prophylaxis (cases) were compared to controls (no VTE). A univariate analysis was conducted (p < 0.05 statistically significant). Seven VTE cases were identified from 234 TKA-patients. Patients with and without VTE had BMI of 40.1 ± 9.1 and 32.8 ± 7.5, respectively (p = 0.064). TTI_RIV in VTE and control group was 28.2 ± 4.7 hours and 26.4 ± 4.2 hours, respectively (p = 0.39). Mean tourniquet time in VTE and control group was 65.0 ± 8.7 minutes and 49 ± 8.8 minutes, respectively (p = 0.0007). Statistically significant differences in tourniquet times were noted between VTE and non-VTE group but not for TTI_RIV and BMI. Prolonged tourniquet use could pose a potential risk factor for postoperative VTE. Thromboprophylaxis management may need to be adjusted, based on patient-specific factors that could include increasing doses of oral anticoagulants and/or mechanical prophylaxis. However, further large-scale studies are required to establish pathophysiology.

Perioperative Complications Stratified by Body Mass Index for the Direct Anterior Approach to Total Hip Arthroplasty

BACKGROUND

Previous studies have addressed the increased risk of perioperative complications in the obese and morbidly obese populations undergoing total hip arthroplasty. Over the last 15 years, the direct anterior approach has increased in popularity. The purpose of this study is to compare the 90-day perioperative complication rate of total hip arthroplasty performed through the direct anterior approach stratified by body mass index (BMI).

METHODS

Perioperative complications both intraoperative and up to 90 days postoperative were identified in a case series of 1808 primary total hip arthroplasties performed through a direct anterior approach. The patients were stratified according to BMI. Demographics of age, side, sex, and American Society of Anesthesiologists score were recorded. Medical and surgical complications including National Surgical Quality Improvement Program complications, length of stay, reoperation rate, readmission rate, and length of operation were recorded. Bivariate analysis and analysis of variance were performed.

RESULTS

Morbidly obese patients (BMI > 40) demonstrated increased American Society of Anesthesiologists scores, increased surgical times with statistically significant increase in number of patients with surgical complications, National Surgical Quality Improvement Program complications, deep infection, and wound breakdown. Grading the severity of complications also demonstrated the morbidly obese had a higher risk of experiencing more severe complications. Underweight patients (BMI < 18.5) demonstrated a statistically significant readmission rate.

CONCLUSION

In stratifying patients undergoing the direct anterior approach for total hip arthroplasty by BMI, a greater rate of surgical complications both in number and in severity occurs with the morbidly obese undergoing total hip arthroplasty through a direct anterior approach.

Results of Cemented Posterior-Stabilized Total Knee Arthroplasty in Obese Patients With an Average 10-Year Follow-Up

BACKGROUND

Obese and morbidly obese patients undergoing primary total knee arthroplasty (TKA) place significant stress at the bone-cement-implant interface over the life of the patient. The purpose of this study is to evaluate results of cemented, posterior-stabilized TKA in obese and morbidly obese patients at an average follow-up of 10 years.

METHODS

Retrospective study of 181 patients who had a cemented, posterior-stabilized TKA between 2000 and 2013 with body mass index >35 at the time of surgery was conducted. Clinical data and radiographs were evaluated along with survivorship, complications, and revisions. Minimum follow-up was 5 years with an average follow-up of 10 years.

RESULTS

There were 135 women and 46 men in the study, with mean age of 60.2 years (range 43-80), mean body mass index of 42.0 (range 35.1-66.1), and an average follow-up of 10 years (range 5-18). There were a total of 39 failures (22%) that underwent revision TKA surgery with mean time to revision of 8 years. Failures included 25 (14%) cases of aseptic loosening; 9 (5%) polyethylene wear; 2 (1%) prosthetic joint infection; and 3 additional revisions for instability, pain, and stiffness. There were a total of 11 cases of isolated tibial component loosening and 13 for both tibial and femoral loosening. Survivorship at 15 years with aseptic loosening as the endpoint was 86.7%, and for all causes 79.6% at 15 years.

CONCLUSION

Aseptic loosening is the leading cause of failure following TKA in obese and morbidly obese patients with decreasing survivorship from 96.1% to 91.2% and 86.7% at 5, 10, and 15 years, respectively.

Bariatric Surgery Prior to Total Hip Arthroplasty Is Cost-Effective in Morbidly Obese Patients

BACKGROUND

The cost-effectiveness of bariatric surgery to achieve weight loss prior to total hip arthroplasty (THA), and decrease the complications and costs associated with THA in the morbidly obese, is unknown. This study evaluated the cost-effectiveness of bariatric surgery prior to THA for morbidly obese patients with end-stage hip osteoarthritis (OA).

METHODS

A state-transition Markov model was constructed to compare the cost-utility of 2 treatment protocols for patients with morbid obesity and end-stage hip OA: (1) immediate THA and (2) bariatric surgery 2 years prior to THA (combined protocol). The analysis was performed from both a payer and a societal perspective using direct and indirect costs over a 40-year time horizon. Utilities, associated costs, and probabilities for health state transitions were derived from the literature. One-way, 2-way and probabilistic sensitivity analyses were performed to validate the robustness of the base case results, using the standard willingness-to-pay threshold of $100,000/quality-adjusted life years.

RESULTS

From the societal perspective, the combined protocol was more effective (13.16 vs 12.26) with less cost ($91,717 vs $92,684) and thus was the dominant strategy over immediate THA. These results were stable across broad ranges for independent model variables. Monte Carlo simulation with 100,000 samples demonstrated that bariatric surgery prior to THA was the preferred cost-effective strategy over 95% of the time from both a societal and payer perspective.

CONCLUSION

In the morbidly obese patient with end-stage hip OA, bariatric surgery prior to THA is a cost-effective strategy for improving quality of life and decreasing societal and payer costs.

LEVEL OF EVIDENCE

II.

Impact of body mass index on hemoglobin level and blood transfusion in total knee arthroplasty: A retrospective case control study

Background

Morbid obesity is a challenge in cases that require total knee arthroplasty, and several studies considered it a contraindication for the procedure due to associated risk of complications, including plummeting hemoglobin levels and subsequent need for a blood transfusion. This study investigated risk factors for blood transfusion in this patient group and considered their relationship to obesity.

Materials and methods

Patients' data were extracted from medical records, including estimated blood loss and perioperative hemoglobin levels. Patients were weighed and measured, and their body mass index (BMI) was calculated and stratified according to international criteria.

Results

A total of 188 patients were included in this study; among them, 136 patients had obesity (72%), with a mean BMI of 33.54. The mean volume of blood lost was 1055.4 ml, with the mean postoperative hemoglobin decrease of 1.42 g/dl and 2.88 g/dl at 6 and 24 h after surgery, respectively. The pre-operative Hb level was the only significant risk factor for blood transfusion. BMI did not affect the risk of blood transfusion or amount of blood lost.

Conclusion

Obesity (BMI > 30 kg/m²) did not increase the risk of needing a blood transfusion after total knee arthroplasty. A judicious transfusion strategy involving the pre-operative Hb optimization should be adopted in TKA to decrease transfusion rate, benefit patient outcomes, and increase healthcare system efficiency. This study shows that high BMI is not a risk factor for postoperative blood transfusion.

Neuro-Immunity Controls Obesity-Induced Pain

The prevalence of obesity skyrocketed over the past decades to become a significant public health problem. Obesity is recognized as a low-grade inflammatory disease and is linked with several comorbidities such as diabetes, circulatory disease, common neurodegenerative diseases, as well as chronic pain. Adipocytes are a major neuroendocrine organ that continually, and systemically, releases pro-inflammatory factors. While the exact mechanisms driving obesity-induced pain remain poorly defined, nociceptor hypersensitivity may result from the systemic state of inflammation characteristic of obesity as well as weight surplus-induced mechanical stress. Obesity and pain also share various genetic mutations, lifestyle risk factors, and metabolic pathways. For instance, fat pads are often found hyper-innervated and rich in immune cell types of multiple origins. These immunocytes release cytokines, amplifying nociceptor function, which, in turn, via locally released neuropeptides, sustain immunocytes' function. Here, we posit that along with mechanical stress stemming from extra weight, the local neuro-immune interplay occurring within the fat pads maintains the state of chronic low-grade inflammation and heightens sensory hypersensitivity. Overall, stopping such harmful neuro-immune crosstalk may constitute a novel pathway to prevent obesity-associated comorbidities, including neuronal hypersensitivity.

Obesity Alters Spinopelvic Alignment Changes From Standing to Relaxed Sitting: the Influence of the Soft-tissue Envelope

Background

Changes in spinopelvic and lower extremity alignment between standing and relaxed sitting have important clinical implications with regard to stability of total hip arthroplasty. This study aimed to analyze the effect of body mass index (BMI) on lumbopelvic alignment and motion at the hip joint.

Methods

A retrospective review of patients who underwent full-body stereoradiographs in standing and relaxed sitting for total hip arthroplasty planning was conducted. Spinopelvic parameters measured included spinopelvic tilt (SPT), pelvic incidence (PI), lumbar lordosis (LL), PI minus LL (PI-LL), proximal femoral shaft angle (PFSA), and standing-to-sitting hip range of motion. Propensity score matching controlled for age, gender, PI, and hip ostoarthritis grade. Patients were stratified into normal (NORMAL; BMI, 18.5-24.9), overweight (OW; 25.0-29.9), and obese (OB; 30.0-34.9) groups. Alignment parameters were compared using one-way analysis of variance.

Results

There were 84 patients in each group after propensity score matching. Standing alignment between BMI groups was similar for all parameters (P > .05) except for PFSA (P < .001). Significant differences were noted for sitting alignment between patients who are NORMAL, OW, and OB in: SPT (P = .007), PI-LL (P = .018), and LL (P = .029). PFSA between groups was not significantly different (P > .05). Significant differences were found for sitting-to-standing alignment across groups in PFSA change (P < .001), SPT change (P = .006), PI-LL change (P = .005), LL change (P = .037), and hip flexion (P < .001).

Conclusions

Significant differences in sitting and standing-to-sitting change in lumbopelvic alignment based on BMI suggest obese patients recruit more posterior spinopelvic tilt when sitting to compensate for soft-tissue impingement that occurs anterior to the hip joint and limiting hip flexion.

Ten-year risk of complication and mortality after total hip arthroplasty in morbidly obese patients: a population study

Background

The relationship between morbid obesity and long-term patient outcomes after primary total hip arthroplasty (THA) has been understudied. The purpose of this study was to determine the association between morbid obesity and 10-year complications (revision surgery, reoperation, dislocation) and mortality in patients undergoing primary THA.

Methods

We conducted a population-based cohort study of patients aged 45–74 years who underwent primary THA for osteoarthritis between 2002 and 2007 using Ontario administrative health care databases. Patients were followed for 10 years. We estimated risk ratios (RRs) of mortality, reoperation, revision and dislocation in patients with body mass index (BMI) greater than 45 kg/m2 (morbidly obese patients) compared with patients with a BMI of 45 kg/m2 or less (nonmorbidly obese patients).

Results

There were 22 251 patients in the study cohort, of whom 726 (3.3%) were morbidly obese. Morbid obesity was associated with higher 10-year risk of death (RR 1.38, 95% confidence interval [CI] 1.18–1.62). Risks of revision (RR 1.43, 95% CI 0.96–2.13) and dislocation (RR 2.38, 95% CI 1.38–4.10) were higher in morbidly obese men than in nonmorbidly obese men; there were no associations between obesity and revision or dislocation in women. Risk of reoperation was higher in morbidly obese women than in nonmorbidly obese women (RR 1.59, 95% CI 1.05–2.40); there was no association between obesity and reoperation in men.

Conclusion

Morbidly obese patients undergoing primary THA are at higher risk of long-term mortality and complications. There were differences in complication risk by sex. The results of this study should inform perioperative counselling of patients considering THA.

Obesity is Associated with an Increased Prevalence of Glenohumeral Osteoarthritis and Arthroplasty: A Cohort Study

The relationship between obesity and glenohumeral osteoarthritis is relatively understudied. The purpose of this study was to better define this relationship by age- and gender-matching 596,874 patients across six body mass index (BMI) cohorts and determining the prevalence of glenohumeral osteoarthritis and the standardized rate of glenohumeral arthroplasty in each cohort. Individuals with a BMI over 24 were found to be at increased odds for developing glenohumeral osteoarthritis, compared to the normal BMI cohort, and individuals with a BMI over 30 were additionally found to be at increased odds for undergoing glenohumeral arthroplasty.

Association of body mass index and osteoarthritis with healthcare expenditures and utilization

OBJECTIVE

Osteoarthritis is highly prevalent and, on aggregate, is one of the largest contributors to US spending on hospital-based health care. This study sought to examine body mass index (BMI)-related variation in the association of osteoarthritis with healthcare utilization and expenditures.

METHODS

This is a retrospective study using administrative insurance claims linked to electronic health records. Study patients were aged ≥ 18 years with ≥1 BMI measurement recorded in 2014, with the first (index) BMI ≥ 25 kg m-2. Study outcomes and covariates were measured during a 1-year evaluation period spanning 6 months before and after index. Multivariable regression analyses examined the association of BMI with osteoarthritis prevalence, and the combined associations of osteoarthritis and BMI with osteoarthritis-related medication utilization, all-cause hospitalization, and healthcare expenditures.

RESULTS

A total of 256 459 patients (median age = 56 y) met study eligibility criteria; 14.8% (38 050) had osteoarthritis. In multivariable analyses, the adjusted prevalence of osteoarthritis increased with increasing BMI (12.7% in patients who were overweight [25.0-29.9 kg m-2] to 21.9% in patients with class III obesity [BMI ≥ 40 kg m-2], P < .001). Among patients with osteoarthritis, increasing BMI (from overweight to class III obesity) was associated with increased (all P < .01): utilization rates for analgesic medications (41.5-53.5%); rates of all-cause hospitalization (26.3%-32.0%); and total healthcare expenditures ($18 204-$23 372).

CONCLUSION

The prevalence and economic burden of osteoarthritis grow with increasing BMI; primary prevention of weight-related osteoarthritis and secondary weight management may help to alleviate this burden.

Obesity Treatment: A Focus on Pharmacotherapy of Weight Management

Obesity, a chronic multifactorial disease, has been on the rise in the United States in recent years. It paves a way to other chronic conditions and related morbidity and mortality. The treatment of obesity should have a chronic approach involving lifestyle modifications from the very beginning. Along with reduced calorie diet, increased physical activity, and behavior modifications, various short- and long-term pharmacological agents are available to help with the weight loss. For qualifying patients, selection of an appropriate agent based on its mechanism, efficacy, and safety profile as well as patient preference can provide desired outcomes. This medical weight management should be a multidisciplinary approach involving nurses to provide continuous patient education and motivation.

Does body mass index affect the rate of adverse outcomes in total hip and knee arthroplasty? A retrospective review of a total joint replacement database

Background

Total hip arthroplasty (THA) and total knee arthroplasty (TKA) are reliable surgical options to treat pain and disability resulting from degenerative conditions around the hip and knee. Obesity is a modifiable risk factor that contributes to significant morbidity. The purpose of this study was to retrospectively compare outcomes in primary hip and knee arthroplasty for patients with increased body mass index (BMI) and those with normal BMI, using data from the registry of the Alberta Bone and Joint Health Institute (ABJHI).

Methods

We retrospectively reviewed the data compiled in the ABJHI registry between March 2010 and July 2016. We reviewed outcomes with respect to length of stay, discharge destination, 30-day readmission, postoperative infection, postoperative transfusion requirements, postoperative adverse events and in-hospital postoperative mechanical complications.

Results

A total of 10 902 patients (6076 women, 4826 men) who underwent THA and 16 485 patients (10 057 women, 6428 men) who underwent TKA were included in the study. For both THA and TKA, patients with increased BMI had an increased number of in-hospital medical events, had an increased rate of deep infection, were less likely to be discharged home (p < 0.001) and had decreased transfusion requirements (p < 0.001) than patients whose weight was in the normal range. Increased BMI increased the rate of 30-day readmission and length of stay in the THA cohort but not in the TKA cohort. Increased BMI had no effect on acute postoperative dislocation or periprosthetic fractures. Patients with a BMI of 30 kg/m2 or greater required a THA 1.7 years earlier than patients of normal weight, patients whose BMI was 35 kg/m2 or greater required a THA 3.4 years earlier, and patients whose BMI was 40 kg/m2 or greater required a THA 5.8 years earlier. In the TKA cohort, patients with a BMI of 30 kg/m2 or greater required a TKA 2.7 years earlier than patients whose weight was in the normal range, patients with a BMI of 35 kg/m2 or greater required a TKA 4.6 years earlier, and patients whose BMI was 40 kg/m2 or greater required a TKA 7.6 years earlier.

Conclusion

Our study quantifies the effects of obesity in primary hip and knee arthroplasty. It provides a greater understanding of the risks in the obese population when contemplating joint arthroplasty.

The effect of body mass index on 30-day complications after total hip arthroplasty

BACKGROUND

Evaluating body mass index (BMI) as a continuous variable eliminates the potential pitfalls of only considering BMI as a binary or categorical variable, as most studies do when correlating BMI and total hip arthroplasty (THA) outcomes. Therefore, the objective of this study was to correlate the effect of continuous BMI on 30-day complications post-THA. Specifically, we correlated BMI to: (1) 30-day readmissions and reoperations; (2) medical complications; and (3) surgical complications in: (a) normal-weight; (b) over-weight; (c) obese; and (d) morbidly obese patients.

METHODS

Using the NSQIP database, 93,598 primary THAs were identified. 30-day rates of readmissions, reoperations, and medical/surgical complications as well as patient BMI data were extrapolated. A comparative analysis using univariate, multivariate, and spline regression models adjusting for demographics and comorbidities were created to study the continuous effect of BMI on different outcomes.

RESULTS

Readmission (p < 0.001), reoperation (p = 0.007), superficial infection (p = 0.003), prosthetic joint infection (p < 0.001), and sepsis (p = 0.026) had a J-shaped relationship with BMI, with the lowest rates seen in patients with BMI around 28 kg/m². The risks of mortality (p = 0.007) and transfusion (p < 0.001) had a reverse J-shaped relationship, with the risk steadily decreasing for BMIs in the normal weight and overweight range, and then flattening afterwards.

CONCLUSION

This data proposes a multifactorial effect of BMI on post-THA complications. Considering BMI as a continuous variable allows for a better assessment when considering the interplay between modifiable risk factors, such as smoking or alcohol use, as well as multiple comorbidities.

The Influence of Obesity on Hip Pain, Function, and Satisfaction 10 Years Following Total Hip Arthroplasty

BACKGROUND

The prevalence of obesity is rising, and increasing numbers of joint arthroplasty surgeries are being performed on obese patients. Concern exists that obesity increases surgical risk; however, its impact on function following total hip arthroplasty (THA) is inconsistently affirmed and less understood. A paucity exists in the literature pertaining long-term objective functional measures. Therefore, we investigated the impact of obesity on hip pain, function, and satisfaction 10 years following THA.

METHODS

This single-center, prospective, observational study categorized consecutive THA patients according to their body mass index to nonobese (<30 kg/m²) and obese (≥30 kg/m²) groups. Preoperative assessment included a numerical pain rating and the Oxford Hip Score. These were repeated along with a 6-minute walk test and a Likert satisfaction scale at 3 months, 1, 5, and 10 years postoperatively.

RESULTS

The series included 191 primary THA patients. No significant differences were found in hip pain or function between the obese and nonobese groups. Obese patients however had poorer walking capacity (P = .008), were more likely to use walking aids (P = .04), and were less satisfied (P = .04) at 10 years.

CONCLUSION

THA confers significant long-term symptom resolution irrespective of obesity; however, despite undergoing surgery, obese patients can be counseled they may not be as satisfied as or achieve the same walking capacity as nonobese individuals.

Using Cluster Analysis to Identify Patient Factors Linked to Differential Functional Gains After Total Knee Arthroplasty

BACKGROUND

The basis of poor outcomes following total knee arthroplasty (TKA) is multifactorial. Previous research aimed at predicting outcome following TKA focuses largely on outcomes measured between two specific time points (pre-to post-TKA). Analysis of outcomes measured over multiple time points (trajectory) may expose relationships between patients' characteristics and longitudinal outcome patterns that may otherwise remain obscured.

METHODS

The current study analyzed Short Form 36 Physical Component Score (PCS) trajectories of 656 patients composed of 3 time points over a 1-year period. Clusters were constructed utilizing MultiExperiment Viewer hierarchical clustering algorithm. Statistical significance of these clusters was assessed using MeV's built-in bootstrapping method. Patient characteristics of the resulting statistically conserved clusters were summarized and compared using Wilcoxon rank-sum test or chi-squared test as appropriate.

RESULTS

Two distinct clusters of outcome trajectory were identified. Cluster 1 included 550 patients (84%) who demonstrated persistent PCS improvement at 6 and 12 months. Cluster 2 included 106 patients (16%) who demonstrated decline in PCS at 6 months followed by improvement at 12 months. Cluster 1 achieved earlier success, greater absolute mental and physical health scores as compared to Cluster 2 (P < .05), and demonstrated higher baseline mental health scores, lower baseline PCS, and a significantly higher proportion of non-Hispanic Whites (P ≤ .05).

CONCLUSION

Cluster analysis identified distinct functional outcome trajectories following TKA. Specific differentiating patient factors were associated with differing trajectories. Future studies should focus on this method's ability to inform predictive models regarding patient outcomes.

Total Joint Arthroplasty in the Morbidly Obese: How Body Mass Index ≥40 Influences Patient Retention, Treatment Decisions, and Treatment Outcomes

BACKGROUND

The United States is in an obesity epidemic. Obesity has multiple common comorbid conditions, including lower extremity arthritis. We sought to examine the course of treatment for a population with body mass index (BMI) ≥40 kg/m² and osteoarthritis (OA) of the hip or knee. We investigated decision criteria that influenced arthroplasty surgeons to recommend nonoperative management vs total joint arthroplasty (TJA). For those patients who ultimately received TJA, we compared outcomes in this population to those with BMI <40 kg/m².

METHODS

This study retrospectively reviewed 158 new patients with BMI ≥40 kg/m² and moderate/severe OA of the hip or knee. Demographics, comorbidity profiles, and weight loss were compared between groups that underwent TJA and those that did not. The arthroplasty database was used to identify patients who underwent TJA during 2016-2018 (N = 1473). Comorbidities, readmissions, surgical site infections, and overall complications were compared between those with BMI ≥40 kg/m² and BMI <40 kg/m².

RESULTS

About 51.3% of new patients with BMI ≥40 kg/m² and moderate/severe OA did not return for a second clinic visit. Of those who did return, 42.9% eventually underwent surgery. BMI was higher in single visit patients vs those with multiple visits (49.5 vs 46.3 kg/m², P < .001), no difference in those scheduled on an "as-needed" basis vs a specific return date (P = .18), and did not change significantly during the 2-year follow-up (P = .41). Patients who underwent TJA had a lower mean BMI at presentation than their nonoperative counterparts (44.5 vs 47.6 kg/m², P < .01) and demonstrated significant weight loss prior to surgery (44.5 vs 42.6 kg/m², P < .05). When comparing patients with BMI ≥40 kg/m² vs BMI <40 kg/m², overall complications were not higher in the BMI ≥40 kg/m² group, although surgical site infections were higher in those undergoing total hip arthroplasty with BMI ≥40 kg/m² (0.3% vs 3.1%, P < .05).

CONCLUSION

A majority of patients with BMI ≥40 kg/m² and moderate/advanced OA will be lost to orthopedic follow-up. A relatively lower BMI indicates a greater chance of retention in care, and ultimately surgery, but does not influence surgeons' recommendations to continue orthopedic management. Patients who persist in seeking treatment, lose significant weight, and exhaust nonoperative alternatives may be suitable for TJA despite a BMI ≥40 kg/m², with an overall complication rate of 4.3%. However, only 9% of patients at 2-year follow-up achieved BMI <40 kg/m² and only 20% of surgeries were performed on patients who had achieved this proposed cutoff.

Does Bariatric Surgery Normalize Risks After Total Knee Arthroplasty? Administrative Medicare Data

Patients with morbid obesity, defined as body mass index of greater than 40 kg/m², are being referred for weight loss and bariatric surgery before being accepted for a total knee arthroplasty (TKA). Previous studies have identified the risks associated with doing a TKA in an individual with an increased body mass index. We now present data identifying the same risks in individuals who have undergone bariatric surgery before submitting to TKA.

Severe Obesity Increases Risk of Infection After Revision Total Hip Arthroplasty

BACKGROUND

The increasing prevalence of obesity has resulted in an increased number of revision total hip arthroplasties (rTHAs) performed in patients with a high body mass index (BMI). The aim of this study is to evaluate whether obesity negatively affects (1) complication rate, (2) reoperation and revision rate, and (3) patient-reported outcome in rTHA.

METHODS

In this registry-based study, we prospectively followed 444 rTHAs (cup: n = 265, stem: n = 57, both: n = 122) performed in a specialized high-volume orthopedic center between 2013 and 2015. The number of complications, and reoperation and revision surgery was registered until 5 years postoperatively. Oxford Hip Score (OHS) was evaluated preoperatively, and at 1 and 2 years postoperatively. Patients were categorized based on BMI to nonobese (<30 kg/m², n = 328), obese (30-35 kg/m², n = 82), and severe obese (≥35 kg/m², n = 34).

RESULTS

Severe obese patients, but not obese patients, had higher risks of complications and re-revision than nonobese patients. In particular, the risk of infection following rTHA was higher in severe obese patients (24%) compared to nonobese patients (3%; relative risk, 7.7). Severe obese patients had overall poorer OHS than nonobese patients, but improvement in OHS did not differ between severe obese and nonobese patients. No differences between obese and nonobese groups on OHS were observed.

CONCLUSION

In our study, severe obesity was associated with an increased risk of infection following rTHA. Patients with high BMI should be counseled appropriately before surgery.

Reduction of invasive interventions in severely obese with osteoarthritis after bariatric surgery

BACKGROUND

Osteoarthritis (OA) affects 56,000,000 Americans, 30% with obesity. Their risk of developing OA is 5 times higher. With each extra kilogram above ideal weight, the risk of OA increases to 13%. The study aim is to describe changes in OA treatment after undergoing bariatric surgery (BS).

METHODS

After IRB approval, we conducted a retrospective analysis of all severely obese patients and OA that underwent laparoscopic adjustable gastric banding, laparoscopic sleeve gastrectomy (LSG), and laparoscopic Roux-en-Y gastric bypass from 2004 to 2018. Changes of OA severity were assessed based on the requirement of invasive intervention (INI) at 12 and 24 months after BS. INI was defined as the need for surgical drainage; articular injection; and surgical interventions such as meniscectomy, total hip replacement, and total knee replacement.

RESULTS

A total of 11.52% (N = 486) had OA diagnosed prior to BS, the most common location being unilateral hip 31.1% (N = 151). A total of 35.2% (N = 159) of patients required pain management (PM) for OA at 12 months. Of these, 90% (N = 144) required only INI and 5.6% (N = 9) required PM only. Baseline and postoperative BMI were associated to need for INI. At 12 months, the 66.7% (N = 301) who did not require INI had a baseline BMI of 44.70 ± 8.22 and total weight loss percent (TWL%) of 14.29 ± 13 (P = 0.05; 95% CI 0.96-1.00). LSG patients were the majority compared to other procedures (44.5%; N = 134). On the other hand, 64.3% (N = 175) did not require INI at 24 months and had a baseline BMI of 17.82±17.4 and TWL% of 2.43 ± 6 (P = 0.003; 95% CI 1.04-1.25). The risk to require INI was reduced by 69.9% at 12 months and 80% at 24 months. Need for pain medications at 12 months was reduced by 96.9%.

CONCLUSION

According to this study data, bariatric surgery reduces the need for INI in patients with OA. The effect seems to be related to the amount of weight loss. Additional studies conducted on a larger scale are necessary to validate findings.

The Effect of Bariatric Surgery Prior to Lower-Extremity Total Joint Arthroplasty: A Systematic Review

BACKGROUND

Obesity is an independent risk factor for osteoarthritis and has been associated with increased rate of complications following lower-extremity total joint arthroplasty (TJA). Bariatric surgery (BS) is a surgical option for weight loss and for reducing obesity-related comorbidities in morbidly obese patients.

PURPOSE/QUESTIONS

The goal of this systematic review was to answer the following questions: (1) Does BS prior to TJA correlate with lower post-operative complication rates in morbidly obese patients undergoing TJA? (2) Does BS have an impact on revision rates following TJA?

METHODS

Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and checklist, a systematic review of medical databases (PubMed/ MEDLINE, Cochrane Library, Web of Science, and Clinicaltrials.gov) was undertaken for articles published in English from January 1990 to September 2018. Inclusion criteria were studies that included at least ten patients who underwent BS prior to TJA, collected data on complications or other outcomes, and followed patients for at least 90 days after TJA. A descriptive and critical analysis of the results was performed.

RESULTS

From 799 studies, 13 met inclusion criteria. A total of 11,770 patients who had undergone bariatric surgery prior to TJA were analyzed. The quality of the evidence ranged between moderate and high. There was no consensus on the effect of previous BS on early- to short-term outcomes reported after TJA.

CONCLUSION

The literature remains conflicted on the impact of BS prior to TJA on early, short-term, and long-term complications after TJA. Additional well-matched, observational studies may further our understanding of the impact of BS prior to TJA on outcomes. In particular the effect of various types of BS prior to TJA on outcomes has yet to be elucidated. Ideally, prospective studies with higher level of evidence will be more definitive on the effects of BS prior to TJA.Prospero Registration Number: CRD42016043025.

Management of the Bariatric Patient. What Are the Implications of Obesity and Total Joint Arthroplasty: The Orthopedic Surgeon's Perspective?

BACKGROUND

Obesity in the United States has reached epidemic proportions. It is associated with multiple higher rates of osteoarthritis of the hip and knee and thus an increasing need for total hip and knee arthroplasty. The demand for total joint arthroplasty among obese patients has increased and outpaces that of a non-obese cohort. The complications associated with obese patients undergoing hip or knee replacement is well defined in the literature.

METHODS

Many practices have set restriction on body mass index (BMI) prior to elective total join arthroplasty. We review the implications of these BMI cutoffs as it is related to access to care for morbidly obese patients in need of hip and knee arthroplasty.

RESULTS

Of the 289 patients who presented with BMI >40, only 19% of patients underwent total hip or knee arthroplasty at a minimum of 2 years of follow-up.

CONCLUSION

This symposium discusses the implications of withholding surgery in the morbidly obese and sets the stage for the development of more collaborative work to ensure optimal care and optimal outcome for the morbidly obese.

The Effect of Body Mass Index on 30-day Complications After Revision Total Hip and Knee Arthroplasty

BACKGROUND

We aimed to explore the effect of body mass index (BMI) on 30-day complications after aseptic revision total knee arthroplasty (rTKA) and aseptic revision total hip arthroplasty (rTHA), considering BMI as both a categorical and continuous variable.

METHODS

A total of 18,866 patients (9093 rTHA and 9773 rTKA) patients were included for analysis using the American College of Surgeons National Surgical Quality Improvement Project database. Thirty-day rates of readmissions, reoperations, and major and minor complications were compared between different weight categories (overweight: BMI >25 and ≤30 kg/m²; obese: BMI >30 and ≤40 kg/m²; morbidly obese: BMI >40 kg/m²) and the normal weight category (BMI >18.5 and ≤25 kg/m²) using multivariate regression models. Spline regression models were created to study BMI as a continuous variable.

RESULTS

Both readmission rates and reoperation rates increased for rTKA as BMI increased (P < .005). There was a linear relationship between BMI and readmission rates for rTKA. Morbid obesity was associated with an increased reoperation rate for rTHA on univariate analysis (P = .022); however, multivariate analysis showed no statistically significant increase in readmission or reoperation rates as BMI increased for rTHA.

CONCLUSIONS

The relationship between BMI and complications after revision total joint arthroplasty is a J-shaped curve with the lowest rates of complications occurring around a BMI of 30 kg/m². The relationship between BMI and perioperative complications is stronger for revision TKA as opposed to revision THA.

Total hip arthroplasty in obesity: separating 'fat' from fiction

Obesity is a modern-day epidemic with increasing prevalence that is directly impacting the global burden of primary total hip arthroplasty. The risk of requiring total hip arthroplasty for osteoarthritis increases incrementally with increasing obesity class. Surgical intervention in obese patients presents a set of unique challenges that should be recognized by the treating medical team. Although predominantly satisfactory outcomes have been reported, perioperative anaesthetic and surgical concerns require thorough patient assessment. There is an increased potential risk of thrombogenic and septic complications, but the body mass index cutoff level beyond which total hip arthroplasty should not be offered in the obese patient remains controversial. Preoperative medical optimization of the patient and appropriate intraoperative interventions are essential to mitigate the risk of complications.

Morbid Obesity in Revision Total Knee Arthroplasty: A Significant Risk Factor for Re-Operation

BACKGROUND

The purpose of this study is to compare surgical and clinical outcomes between matched groups of morbidly obese (body mass index [BMI] >40 kg/m²) and non-morbidly obese (BMI <40 kg/m²) patients undergoing first-time revision total knee arthroplasty with a minimum 5-year follow-up.

METHODS

Two groups of 87 patients (BMI >40 or <40 kg/m²) were matched 1:1 based on age at the time of revision, gender, and diagnosis for revision (aseptic or septic causes).

RESULTS

The morbidly obese group had a significantly greater incidence of re-operation (34.5% [30/87] vs 16.1% [14/87], P = .005) and re-revision (27.6% [24/87] vs 12.6% [11/87], P = .014) with a significantly lower 10-year survivorship for re-operation (P = .05) and subsequent revision (P = .014). In particular, the aseptic sub-group had a greater incidence of re-operation (29.9% [20/67] vs 13.4% [9/67], P = .021) and re-revision (26.9% [18/67] vs 11.9% [8/67], P = .029). The non-morbidly obese group demonstrated higher final Western Ontario and McMaster Universities Index scores (63.1 ± 19.5 vs 55.5 ± 22.5, P = .030) and a greater change between pre-operative and final KSS (45.6 ± 44.3 vs 39.7 ± 48.4, P = .040) and SF-12 Mental component (3.6 ± 10.8 vs -1.4 ± 10.3, P = .013).

CONCLUSION

Morbidly obese patients undergoing revision total knee arthroplasty have a greater risk of re-operation and re-revision while experiencing lower clinical outcome scores compared to non-morbidly obese patients. These patients should be informed of the higher potential for re-operation and the possibility of poor results.

Obese patients have higher rates of polymicrobial and Gram-negative early periprosthetic joint infections of the hip than non-obese patients

Background

Obese patients are more likely to develop periprosthetic joint infection (PJI) after primary total joint arthroplasty. This study compared the clinical and microbiological characteristics of non-obese, obese and severely obese patients with early PJI, in order to ultimately optimize antibiotic prophylaxis and other prevention measures for this specific patient category.

Methods

We retrospectively evaluated patients with early PJI of the hip and knee treated with debridement, antibiotics and implant retention (DAIR) between 2006 and 2016 in three Dutch hospitals. Only patients with primary arthroplasties indicated for osteoarthritis were included. Early PJI was defined as an infection that developed within 90 days after index surgery. Obesity was defined as a BMI ≥30kg/m² and severe obesity as a BMI ≥35kg/m².

Results

A total of 237 patients were analyzed, including 64 obese patients (27.0%) and 62 severely obese patients (26.2%). Compared with non-obese patients, obese patients had higher rates of polymicrobial infections (60.3% vs 33.3%, p<0.001) with more often involvement of Enterococcus species (27.0% vs 11.7%, p = 0.003). Moreover, severely obese patients had more Gram-negative infections, especially with Proteus species (12.9% vs 2.3%, p = 0.001). These results were only found in periprosthetic hip infections, comprising Gram-negative PJIs in 34.2% of severely obese patients compared with 24.7% in obese patients and 12.7% in non-obese patients (p = 0.018).

Conclusions

Our results demonstrate that obese patients with early periprosthetic hip infections have higher rates of polymicrobial infections with enterococci and Gram-negative rods, which stresses the importance of improving preventive strategies in this specific patient category, by adjusting antibiotic prophylaxis regimens, improving disinfection strategies and optimizing postoperative wound care.

Osteochondral Allograft Transplantation of the Knee in Patients with an Elevated Body Mass Index

OBJECTIVE

To characterize the graft survivorship and clinical outcomes of osteochondral allograft transplantation (OCA) of the knee in patients with an elevated body mass index (BMI).

DESIGN

Prospective data on 38 consecutive patients with a BMI ≥30 kg/m² treated with OCA from 2000 to 2015 were reviewed. Complications, reoperations, and patient responses to validated outcome measures were examined. Failures were defined by any removal/revision of the allograft or conversion to arthroplasty.

RESULTS

Thirty-one knees in 31 patients (mean age, 35.4 years [range, 17-61 years]; 87% male) met the inclusion criteria. Mean BMI was 32.9 kg/m² (range, 30-39 kg/m²). Mean chondral defect size was 6.4 cm² (range, 1.0-15.3 cm²). Prior to OCA, 23 patients (74%) had undergone previous surgery to the ipsilateral knee. Mean duration of follow-up was 4.1 years (range, 2-11 years). After OCA, 5 knees (13%) underwent conversion to unicompartmental (1) or total (4) knee arthroplasty. Two- and 5-year graft survivorship were 87% and 83%, respectively. At final follow-up, clinically significant improvements were noted in the pain (49.3-72.6) and physical functioning (52.9-81.3) subscales of the Short Form-36 ( P ≤ 0.001), International Knee Documentation Committee subjective form (43.5-67.0; P = 0.002), Knee Outcome Survey-Activities of Daily Living (58.2-80.4; P = 0.002), and overall condition subscale of the Cincinnati Knee Rating System (4.7-6.9; P = 0.046).

CONCLUSIONS

OCA can be a successful midterm treatment option for focal cartilage defects of the knee in select patients with a BMI ≥30 kg/m².

Accuracy and Precision of Acetabular Component Placement With Imageless Navigation in Obese Patients

BACKGROUND

Obesity is a risk factor for acetabular component malposition when total hip arthroplasty is performed with manual techniques. The utility of imageless navigation in obese patients remains unknown. This study compared the accuracy and precision of imageless navigation for component orientation between obese and nonobese patients.

METHODS

A total of 459 total hip arthroplasties performed for osteoarthritis using imageless navigation were reviewed from a single surgeon's institutional review board-approved database. Einzel-Bild-Roentgen Analyse determined component orientation on 6-week postoperative anteroposterior radiographs. Mean orientation error (accuracy) and precision were compared between obese (body mass index ≥ 30 kg/m²) and nonobese patients. Regression analysis evaluated the influence of obesity on component position.

RESULTS

The difference in mean inclination and anteversion between obese and nonobese groups was 1.1° (43.0° ± 3.5°; range, 35.8°-57.8° vs 41.9° ± 4.4°; range, 33.0°-57.1° and 24.9° ± 6.3°; range, 14.2°-44.3° vs 23.8° ± 6.6°; range, 7.0°-38.6°, respectively). Inclination precision was better for nonobese patients. No difference in inclination accuracy or anteversion accuracy or precision was detected between groups. And 83% of components were placed within the target range. There was no relationship between obesity (dichotomized) and component placement outside the target ranges for inclination, anteversion, or both. As a continuous variable, increased body mass index correlated with higher odds of inclination outside the target zone (odds ratio, 1.06; P = .001).

CONCLUSION

Using imageless navigation, inclination orientation was less precise for obese patients, but the observed difference is likely not clinically relevant. Accurate superficial registration of landmarks in obese patients is achievable, and the use of imageless navigation similarly improves acetabular component positioning in obese and nonobese patients.

LEVEL OF EVIDENCE

Therapeutic Level IV.

Ninety-Day Costs, Reoperations, and Readmissions for Primary Total Hip Arthroplasty Patients of Varying Body Mass Index Levels

BACKGROUND

The purpose of this study is to compare 90-day costs and outcomes for primary total hip arthroplasty patients between a nonobese (body mass index, 18.5-24.9) vs overweight (25-29.9), obese (30-34.9), severely obese (35-39.9), morbidly obese (40-44.9), and super obese (45+) cohorts.

METHODS

We conducted a retrospective review of an institutional database of primary total hip arthroplasty patients from 2006 to 2013. Thirty-three super-obese patients were identified, and the other 5 cohorts were randomly selected in a 2:1 ratio (n = 363). Demographics, 90-day outcomes (costs, reoperations, and readmissions), and outcomes after 3 years (revisions and change scores for Short-Form Health Survey, Harris Hip Score, and Western Ontario and McMaster Universities Arthritis Index) were collected. Costs were determined using unit costs from our institutional administrative data for all in-hospital resource utilization. Comparisons between the nonobese and other groups were made with Kruskal-Wallis tests for non-normal data and chi-square and Fisher exact test for categorical data.

RESULTS

The 90-day costs in the morbidly obese ($13,134 ± $7250 mean ± standard deviation, P < .01) and super-obese ($15,604 ± 6783, P < .01) cohorts were significantly greater than the nonobese cohorts ($10,315 ± 1848). Only the super-obese cohort had greater 90-day reoperation and readmission rates than the nonobese cohort (18.2% vs 0%, P < .01 and 21.2% vs 4.5%, P = .02, respectively). Reoperations and septic revisions after 3 years were greater in the super-obese cohort compared to the nonobese cohort 21.2% versus 3.0% (P = .01) and 18.2% versus 1.5% (P = .01), respectively. Improvements in Short-Form Health Survey, Harris Hip Score, and Western Ontario and McMaster Universities Arthritis Index were comparable in all cohorts.

CONCLUSION

Super-obese patients have greater risks and costs compared to nonobese patients, but also have comparable quality of life improvements.

Obesity and racial characteristics drive utilization of total joint arthroplasty at a younger age

BACKGROUND

Obesity is a growing public health problem. Obesity increases the risk of requiring total joint arthroplasty (TJA). The purpose of this study was to examine the effect of obesity on the propensity for TJA in patients at our institution. We hypothesized that obese patients would be younger and more likely to be races other than non-Hispanic whites when compared to a normal weight cohort.

METHODS

568 consecutive patients undergoing primary TJA were reviewed. Demographic data and World Health Organization Body Mass Index (BMI) class were compared statistically, with age at time of TJA used as the main outcome of interest.

RESULTS

The average age at TKA was 68.3 years, while the average age at THA was 67.5 years (p = 0.447 between procedure groups). Increased BMI class was associated with decreased age at TJA: normal weight patients were 12.2 and 11.4 years older than class III obese patients at the time of TKA and THA, respectively (p < 0.001). Among TKA patients, obese patients, when compared to non-obese patients, were significantly less likely to be non-Hispanic whites (p = 0.016). Among THA patients, class III obese patients were significantly less likely to be non-Hispanic whites (p = 0.007).

CONCLUSIONS

Obesity is a risk factor for both TKA and THA at a younger age. For patients in the study, for each unit increase in BMI, the age at TKA decreased by 0.56 years and age at THA decreased by 0.52 years. Obese patients were less likely to be non-Hispanic whites than normal weight patients.

Increased Survivorship of Cementless versus Cemented TKA in the Morbidly Obese. A Minimum 5-Year Follow-Up

BACKGROUND

Total knee arthroplasty (TKA) in the morbidly obese patients can be challenging with an increased risk of complications. Studies have shown increased aseptic failures with well-aligned cemented TKAs in the obese patient. The purpose of this study is to determine if TKA in the morbidly obese (body mass index [BMI] ≥ 40) using cementless implants would demonstrate improved results and survivorship compared to cemented TKA at a minimum 5-year follow-up.

METHODS

This is a retrospective study comparing clinical results of cemented vs cementless primary TKA with a posterior stabilized design TKA in morbidly obese (BMI ≥ 40) patients with minimal 5-year follow-up. There were 108 patients in the cementless group with a mean BMI of 45.6. In the cemented cohort, there were 85 cemented TKAs with a mean BMI of 45.0. Demographic, clinical, surgical, and radiographic data along with complications were extracted for all study patients.

RESULTS

There were 5 failures requiring revision in the cementless group, including 1 for aseptic tibial loosening (0.9%). In the cemented group, there were 22 failures requiring revision, including 16 implants for aseptic loosening (18.8%; P = .0001). Survivorship with aseptic loosening as the endpoint was 99.1% in the cementless group vs 88.2% in the cemented cohort at 8 years (P = .02).

CONCLUSION

Morbidly obese patients (BMI ≥ 40) have a higher failure due to aseptic loosening with cemented TKA with decreasing survivorship over time. The use of cementless TKA in morbidly obese patients with the potential of durable long-term biologic fixation and increased survivorship appears to be a promising alternative to mechanical cement fixation.

Statistical Methods Dictate the Estimated Impact of Body Mass Index on Major and Minor Complications After Total Joint Arthroplasty

BACKGROUND

Elevated body mass index (BMI) is considered a risk factor for complications after THA and TKA. Stakeholders have proposed BMI cutoffs for those seeking arthroplasty. The research that might substantiate BMI cutoffs is sensitive to the statistical methods used, but the impact of the statistical methods used to model BMI has not been defined.

QUESTIONS/PURPOSES

(1) How does the estimated postarthroplasty risk of minor and major complications vary as a function of the statistical method used to model BMI? (2) What is the prognostic value of BMI for predicting complications with each statistical method?

METHODS

Using the American College of Surgeons National Surgical Quality Improvement Program from 2005 to 2012, we investigated the impact of BMI on major and minor complication risk for THA and TKA. Analyses were weighted with covariate-balancing propensity scores to account for the differential rate of comorbidities across the range of BMI. We specified BMI in two ways: (1) categorically by World Health Organization (WHO) BMI classes; and (2) as a smooth, continuous variable using splines. Models of risk for major complications (deep surgical site infection [SSI], pulmonary embolism, stroke, cardiac arrest, myocardial infarction, wound disruption, implant failure, unplanned intubation, > 48 hours on a ventilator, acute renal insufficiency, coma, sepsis, reoperation, or mortality) and minor complications (superficial SSI, pneumonia, urinary tract infection, deep vein thrombosis, or peripheral nerve injury) were constructed and were adjusted for confounding variables known to correlate with complications (eg, American Society of Anesthesiologists classification). Results were compared for different specifications of BMI. Receiver operating characteristic (ROC) curves were compared to determine the additive prognostic value of BMI.

RESULTS

The type of BMI parameterization leads to different assessments of risk of postarthroplasty complications for BMIs > 30 kg/m and < 20 kg/m with the spline specification showing better fit in all adjusted models (Akaike Information Criteria favors spline). Modeling BMI categorically using WHO classes indicates that BMI cut points of 40 kg/m for TKA or 35 kg/m for THA are associated with higher risks of major complications. Modeling BMI continuously as a spline suggests that risk of major complications is elevated at a cut point of 44 kg/m for TKA and 35 kg/m for THA. Additionally, in these models, risk does not uniformly increase with increasing BMI. Regardless of the method of modeling, BMI is a poor prognosticator for complications with area under the ROC curves between 0.51 and 0.56, false-positive rates of 96% to 97%, and false-negative rates of 2% to 3%.

CONCLUSIONS

The statistical assumptions made when modeling the effect of BMI on postarthroplasty complications dictate the results. Simple categorical handling of BMI creates arbitrary cutoff points that should not be used to inform larger policy decisions. Spline modeling of BMI avoids arbitrary cut points and provides a better model fit at extremes of BMI. Regardless of statistical management, BMI is an inadequate independent prognosticator of risk for individual patients considering total joint arthroplasty. Stakeholders should instead perform comprehensive risk assessment and avoid use of BMI as an isolated indicator of risk.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Obesity in the global haemophilia population: prevalence, implications and expert opinions for weight management

Overweight and obesity may carry a significant disease burden for patients with haemophilia (PWH), who experience reduced mobility due to joint inflammation, muscle dysfunction and haemophilic arthropathy. This review aimed to define the prevalence and clinical impact of overweight/obesity in the global population of PWH. A detailed literature search pertaining to overweight/obesity in haemophilia in the last 15 years (2003-2018) was conducted, followed by a meta-analysis of epidemiological data. The estimated pooled prevalence of overweight/obesity in European and North American PWH was 31%. Excess weight in PWH is associated with a decreased range in motion of joints, accelerated loss of joint mobility and increase in chronic pain. Additionally, the cumulative disease burden of obesity and haemophilia may impact the requirement for joint surgery, occurrence of perioperative complications and the prevalence of anxiety and depression that associates with chronic illness. Best practice guidelines for obesity prevention and weight management, based on multidisciplinary expert perspectives, are considered for adult and paediatric PWH. Recommendations in the haemophilia context emphasize the importance of patient education and tailoring engagement in physical activity to avoid the risk of traumatic bleeding.

Risk of Subsequent Joint Arthroplasty in Contralateral or Different Joint After Index Shoulder, Hip, or Knee Arthroplasty: Association with Index Joint, Demographics, and Patient-Specific Factors

BACKGROUND

The risk of subsequent joint replacement following an index joint replacement for osteoarthritis and the association of this risk with demographic and patient-specific factors are not well understood. The purpose of this study was to determine how demographic and other patient-specific factors are associated with the risk of subsequent joint replacement in the contralateral or a different joint following an index joint replacement for osteoarthritis.

METHODS

The Healthcare Cost and Utilization Project (HCUP) State Inpatient Database (SID) of New York was used to identify the first (primary) total hip arthroplasty (THA), total knee arthroplasty (TKA), or total shoulder arthroplasty (TSA) and the risk of subsequent joint replacement in the contralateral or a different joint over 5 to 8 years. The association of demographic and other patient-specific factors with subsequent joint replacement was assessed via multivariable Cox proportional hazards modeling. We also investigated the time between the index and subsequent joint replacement.

RESULTS

Of 85,616 patients, 20,223 (23.6%) underwent a subsequent replacement of the contralateral joint within 5 to 8 years (median, 343 days) after the index joint replacement. The strongest predictors were obesity (adjusted hazard ratio [HR] = 1.28; p < 0.001) and index TKA compared with THA (1.72; p < 0.001). A total of 3,197 patients (3.7%) underwent a subsequent replacement of a different joint within 5 to 8 years (median, 876 days) after the index joint replacement. The strongest predictors were obesity (adjusted HR = 1.41; p < 0.001) and index TSA compared with THA (adjusted HR = 2.52; p < 0.001).

CONCLUSIONS

There is a relatively high risk of subsequent replacement of the contralateral joint and a relatively low risk of subsequent replacement of a different joint within 5 to 8 years after an index THA, TKA, or TSA. Obesity was associated with a higher risk of subsequent replacement of the contralateral joint or a different joint.

LEVEL OF EVIDENCE

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

Lower Extremity Geometry in Morbid Obesity-Considerations for Total Knee Arthroplasty

BACKGROUND

Obesity has been associated with varying adverse outcomes related to total knee arthroplasty (TKA) and has long been associated with various mechanical complications. Computational modeling holds promise for investigating biomechanical aberrations related to TKA in obese patients. However, basic anthropometric information regarding the shape of the lower extremity in obese patients is lacking. We, therefore, developed a method to determine lower extremity shape both generally and subject specific as a function of body mass index (BMI) and sex.

METHODS

A unique set of 4 radiographs (knee anteroposterior/lateral; EOS long-leg alignment anteroposterior/lateral) were reviewed for patients with BMI exceeding 30 kg/m² before undergoing TKA. Soft tissue thickness in both the coronal and sagittal planes, including anterior adipose tissue thickness overlying the tibial tubercle and patella, was measured. Elliptical parameters were then determined for any distance along the lower extremity. Additional measurements were obtained, including prepatellar thickness and pretubercular thickness and anteroposterior and mediolateral dimensions of the proximal tibia. A total of 232 obese subjects were analyzed.

RESULTS

Girth increased as a function of BMI. Anterior prepatellar and pretubercular subcutaneous fat thickness in females exceeded that in males for all values of BMI. Wide variation was seen with regard to overall patterns of adiposity among same-sex subjects with similar BMI. Proximal tibial osseous dimensions did not demonstrate an association with BMI; however, males were found to have deeper and wider tibias compared with females.

CONCLUSIONS

BMI and sex influence lower extremity shape. The prediction algorithms developed here holds implications for future biomechanical studies of TKA in obese patients.

Severe and morbid obesity and transfusional risk in total knee arthroplasty: An observational study

BACKGROUND

Severe and morbid obesity (Class II -III) represents a challenge for successful knee surgery. There isn't consensus on what influence body mass index has on blood loss and on red blood cell (RBC) transfusion during total knee arthroplasty (TKA). The objective was to determine blood loss and transfusion needs in severe and morbid obese patients undertaking TKA.

METHODS

We recorded retrospectively all patients undergoing TKA. Obesity was assessed according to WHO guidelines. Perioperative haemoglobin and treatments for its optimisation were recorded. Blood losses were estimated from specific formulae for lost red-cell mass and percentage of lost blood volume.

RESULTS

922 patients were included: 35.90% were obese Class I and 18.76% obese Class II - III. Estimated blood volume was 4390  ±  470 ml, 4736  ±  423 ml and 5030 ± 464 ml among non-obese, obese Class I and obese Class II-III, respectively (P < 0.001). The global estimated blood volume (EBV) lost was 1502  ±  680 ml without differences between the three groups. However, the percentage of lost blood volume was lower in obese Class II -III (29.65%) than in non-obese (33.55%) and obese Class I (30.97%) (P < 0.005). Transfusion rates were 12.7%, 12.1% and 6.4% for non-obese, obese Class I and Class II -III, respectively (P = 0.062). A negative transfusion risk was predicted for Class II -III patients.

CONCLUSIONS

Severely and morbidly obese patients did not show greater blood loss nor higher RBC transfusion needs after primary TKA than non-obese and obese Class I patients. This could be because obese Class II -III patients had higher EBV but similar RBC losses.

Dislocation rate increases with bariatric surgery before total hip arthroplasty

INTRODUCTION

Annually in the USA, 113,000 patients with refractory obesity undergo bariatric surgery (BS), and a subset does so in order to lower body mass index to become a more desirable total hip arthroplasty (THA) candidate. This study aims to evaluate THA risk with and without bariatric surgery.

METHODS

12,160 patients were identified in a claim-based review of the entire Medicare database with ICD-9 codes to identify patients in three groups. Patients who underwent BS prior to THA (Group I: 1,545 experimental group) and two control groups that did not undergo BS but had either a body mass index >40 (Group II: 6,918 bariatric control) or <25 (Group III: 3,697 normal weight control). Preoperative demographics/comorbidities and short-term medical (30 day) and long-term surgical (90-day and 2-year) complications were evaluated.

RESULTS

Group I had female predominance, youngest age, and highest incidence of: deficiency anaemia, cardiovascular disease, liver disease, diabetes, polysubstance abuse, psychiatric disorders and smoking. At 2 years, Group I had approximately twice the dislocation and revision risk compared to both Groups II and III; Groups I and II had over four times the risk of infection and wound complications compared to Group III.

CONCLUSION

In the Medicare population, these patients continue to have complication rates similar to and sometimes greater than obese patients with no prior bariatric surgery. Greater dislocation risk is possibly due to ligamentous laxity related to decreased collagen/elastin and/or component malposition due to intraoperative visualisation challenges.

Bariatric Surgery Improves Outcomes After Lower Extremity Arthroplasty in the Morbidly Obese: A Propensity Score-Matched Analysis of a New York Statewide Database

BACKGROUND

The purpose of this study was to compare risks for revision and short-term complications after total joint arthroplasty (TJA) in matched cohorts of morbidly obese patients, receiving and not receiving prior bariatric surgery.

METHODS

Patients undergoing elective TJA between 1997 and 2011 were identified in a New York Statewide database, analyzing total knee arthroplasty (TKA) and total hip arthroplasty (THA) separately. Propensity scores were used to match morbidly obese patients receiving and not receiving bariatric surgery prior to TJA. Cox proportional hazard modeling assessed revision risk. Logistic regression evaluated odds for complications.

RESULTS

For TKA, 2636 bariatric surgery patients were matched to 2636 morbidly obese patients. For THA, 792 bariatric surgery patients were matched to 792 morbidly obese patients. Matching balanced all covariates. Bariatric surgery reduced co-morbidities prior to TJA (TKA P < .0001; THA P < .005). Risks for in-hospital complications were lower for THA and TKA patients receiving prior bariatric surgery (odds ratio [OR] 0.25, P < .001; and OR = 0.69, P = .021, respectively). Risks for 90-day complications were lower for TKA (OR 0.61, P = .002). Revision risks were not different for either THA (P = .634) or TKA (P = .431), nor was THA dislocation risk (P = 1.000).

CONCLUSION

After accounting for relevant selection biases, bariatric surgery prior to TJA was associated with reduced co-morbidity burden at the time of TJA and with reduced post-TJA complications. However, bariatric surgery did not reduce the risk for revision surgery for either TKA or THA.

Ninety-Day Costs, Reoperations, and Readmissions for Primary Total Knee Arthroplasty Patients With Varying Body Mass Index Levels

BACKGROUND

We compared 90-day costs and outcomes for primary total knee arthroplasty patients among nonobese (body mass index [BMI] 18.5-24.9), overweight (25-29.9), obese (30-34.9), severely obese (35-39.9), morbidly obese (40-49.9), and super-obese (50+) cohorts.

METHODS

We conducted a retrospective review of an institutional database of total knee arthroplasty patients from 2006 to 2013 with a minimum of 3-year follow-up. Sixty-five super-obese patients were identified, and five other cohorts were randomly selected in a 2:1 ratio (total, n = 715). Demographics, 90-day outcomes (costs, reoperations, and readmissions), and outcomes after 3 years (revisions and change scores for Short-Form Health Survey [SF-12], Knee Society Scores, and Western Ontario and McMaster Universities Arthritis Index) were aggregated.

RESULTS

The 90-day costs were significantly greater in the morbidly obese ($11,568 ± $1,960) and super-obese ($14,021 ± $7,903) cohorts relative to the smaller BMI cohorts ($9,938 - $10,352). The increased cost from readmissions was the main driver of costs. The outcome change scores were similar across all the BMI cohorts for Knee Society Scores, SF-12 Mental Health Composite Score, and Western Ontario and McMaster Universities Arthritis Index, but not for the SF-12 Physical Health Composite Score. At the midterm follow-up, there was no statistical difference in repeat surgery or aseptic revision rates. Septic revisions were significantly greater in the super-obese cohort relative to the other cohorts (6.2% vs 0.8-3.1%).

CONCLUSION

Health-care policy based purely on the economic costs may place morbidly obese and super-obese patients at risk of losing arthroplasty care, thereby denying them access to the comparable quality of life improvements.

The Impact of Obesity on Orthopedic Upper Extremity Surgery

Obese patients have increased rates of upper extremity injury, carpal tunnel syndrome, and upper extremity osteoarthritis. Preoperative considerations include cardiovascular disease, pulmonary disease, and diabetes mellitus. Intraoperative and anesthetic considerations include specialized equipment, patient positioning, and the physiology of obese patients. Postoperative considerations should include increased risk of cardiovascular complications as well as surgical site infections and malunion. Surgery of the hand and upper extremity may be less prone to the postoperative complications seen in other regions of the body. There are currently no direct contraindications for obese patients to undergo orthopedic procedures if the appropriate considerations have been made.

Obesity: The Modifiable Risk Factor in Total Joint Arthroplasty

Obesity is an epidemic in the health care system. Obesity poses several challenges and raises unique issues for the arthroplasty surgeon. Obese patients are at higher risk for infection and dislocation. Additionally, obese patients have poorer implant survivorship and functional scores postoperatively. Obesity is a modifiable risk factor and weight loss preoperatively should be strongly considered. Obese patients must be counseled so that they have realistic expectations after total joint arthroplasty.

Risk Reduction Compared with Access to Care: Quantifying the Trade-Off of Enforcing a Body Mass Index Eligibility Criterion for Joint Replacement

BACKGROUND

Morbidly obese patients with severe osteoarthritis benefit from successful total joint arthroplasty. However, morbid obesity increases the risk of complications. Because of this, some surgeons enforce a body mass index (BMI) eligibility criterion above which total joint arthroplasty is denied. In this study, we investigate the trade-off between avoiding complications and restricting access to care when enforcing BMI-based eligibility criteria for total joint arthroplasty.

METHODS

In this retrospective cohort study, the Veterans Health Administration (VHA) Corporate Data Warehouse (CDW) and Veterans Affairs Surgical Quality Improvement Program (VASQIP) databases were reviewed for patients undergoing total joint arthroplasty from October 2011 through September 2014. We determined, if various BMI eligibility criteria had been enforced over that period of time, how many short-term complications would have been avoided, how many complication-free surgical procedures would have been denied, and the positive predictive value of BMI eligibility criteria as tests for major complications. To provide a frame of reference, we also determined what would have happened if eligibility for total joint arthroplasty were arbitrarily determined by flipping a coin.

RESULTS

In this study, 27,671 total joint arthroplasties were reviewed. With a BMI criterion of ≥40 kg/m, 1,148 patients would have been denied a surgical procedure free of major complications, and 83 patients would have avoided a major complication. The positive predictive value of a complication using a BMI of ≥40 kg/m as a test for major complications was 6.74% (95% confidence interval [CI], 5.44% to 8.33%). The positive predictive value of a complication using a BMI criterion of 30 kg/m was 5.33% (95% CI, 4.99% to 5.71%). Flipping a coin had a positive predictive value of 5.05%.

CONCLUSIONS

A 30 kg/m criterion for total joint arthroplasty eligibility is marginally better than flipping a coin and should not determine surgical eligibility. With a BMI criterion of ≥40 kg/m, the number of patients denied a complication-free surgical procedure is about 14 times larger than those spared a complication. Although the acceptable balance between avoiding complications and providing access to care can be debated, such a quantitative assessment helps to inform decisions regarding the advisability of enforcing a BMI criterion for total joint arthroplasty.

LEVEL OF EVIDENCE

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

Mortality Following Bariatric Surgery Compared to Other Common Operations in Finland During a 5-Year Period (2009-2013). A Nationwide Registry Study

PURPOSE

A concern regarding the safety of bariatric surgery may explain the fact that only a minor fraction of morbidly obese patients has access to it. This is a population-based, nationwide study reporting 30-day, 90-day, and 1-year mortality rates following bariatric surgery in comparison with mortality rates after other common operations in Finland.

MATERIALS AND METHODS

Patients undergoing surgery between January 2009 and December 2013 were included. Data on surgical procedures were obtained from the national hospital discharge registry, and cause of death was obtained from Statistics Finland.

RESULTS

Inclusion criteria were met by 156,536 patients. Of these, 3918 underwent surgery for morbid obesity. Three patients (0.08%) died within 30 days following bariatric surgery. The 30-day mortality rate was lower only following prostatectomy. Compared with bariatric surgery, the hazard ratios (HR) for 1-year postoperative mortality were significantly higher for elective cholecystectomy (HR 2.38, 95% CI 1.39-4.08, p = 0.002), hysterectomy (HR 2.87, 95% CI 1.68-4.92, p < 0.001), knee arthroplasty (HR 2.23, 95% CI 1.31-3.81, p = 0.003), hip arthroplasty (HR 11.7, 95% CI 6.90-19.8, p < 0.001), colorectal resections (HR 27.5, 95% CI 16.2-46, p < 0.001), gastric resection (HR 53.0, 95% CI 30.2-93.2, p < 0.001), gastrectomy (HR 74.7, 95% CI 43.0-130, p < 0.001), and coronary artery bypass grafting (HR 30.7, 95% CI 17.4-54.3, p < 0.001).

CONCLUSION

Mortality rates following bariatric surgery are low and similar or lower than mortality rates following all other common elective surgeries.

Change in Body Mass Index After Total Knee Arthroplasty and Its Influence on Functional Outcome

BACKGROUND

There is often an assumption by patients that weight loss will occur once their knee pain is relieved by total knee arthroplasty (TKA). This study aims to evaluate (1) the change in patients' body mass index (BMI) after TKA; (2) if postoperative change in BMI influences functional outcome and survival rate of TKA; and (3) the predictive factors associated with change in BMI.

METHODS

Seven thousand seven hundred thirty-three patients who underwent a primary TKA between 2001 and 2010 were included in this study. Functional outcome scores collected at 2 years after surgery include the Oxford Knee Score, Knee Society Function Score, Knee Society Knee Score, Physical Component Score, and Mental Component Score of short form 36.

RESULTS

Among these patients, 1067 (14%) had reduction in BMI, 5045 (65%) maintained their BMI, and 1621 (21%) had gain in BMI. The differences in improvement in Oxford Knee Score, Knee Society Function Score, Knee Society Knee Score, and Physical Component Score among the 3 groups of patients were less than the known minimal clinically important difference of these scores. The 10-year survival rate of TKA was not influenced by patients' change in BMI after surgery (P = .435). Obese class I, II, and III patients were more likely to reduce their BMI after TKA than those with normal preoperative BMI (P = .002, P = .012, and P = .004, respectively), while older patients were less likely to have gain in BMI after surgery (P = .001).

CONCLUSION

A change in BMI after TKA did not influence the functional outcome clinically or the survival rate of the TKA implant.