Surgical site infection and transfusion rates are higher in underweight total knee arthroplasty patients

Incidence and Risk Factors for Acid-fast Bacillus/Fungal Culture Positivity in Primary, Conversion, and Revision Hip and Knee Arthroplasty

INTRODUCTION

Previous literature has reported minimal incidences of positive fungal/AFB cultures, questioning the routine use of these tests. With growing concern for excessive use, predictive factors for patients at higher risk for intraoperative AFB/fungal infections would help surgeons limit unnecessary testing. This study evaluates the positivity rate and predictive factors of positive fungal and/or acid-fast bacillus (AFB) cultures after primary, conversion, or revision hip and knee arthroplasty.

METHOD

Two hundred thirty-eight knee and hip procedures were done between January 2007 and 2022 where intraoperative AFB/fungal cultures were obtained. Procedures included primary total knee arthroplasty, primary total hip arthroplasty, conversion, first of two-stage, second of two-stage, irrigation and débridement polyexchange, and aseptic revision. Positivity rates of intraoperative AFB/fungal cultures were calculated as binomial exact proportions with 95% confidence intervals and are displayed as percentages. Univariable generalized linear mixed models estimated the unadjusted effects of demographics, individual comorbid conditions, and procedural characteristics on the logit of positive AFB/fungal cultures.

RESULTS

Two hundred thirty-eight knee and hip procedures recorded an overall positivity rate of 5.8% for intraoperative AFB/fungal cultures. Aseptic revisions showed the lowest rates of positivity at 3.6%, while conversions showed the highest rates of positivity at 14.3%. The positivity rates are highest among patients who are male (9.0%), of Hispanic origin (12.0%), with body mass index <30 (6.4%), and a Charlson Comorbidity Index <5 (6.1%). History of a prior infection in the same surgical joint showed statistically significant influence of odds of culture positivity with an odds ratio of 3.47 ( P -value: 0.039). Other demographic factors that we investigated including age, sex, race, ethnicity, body mass index, and Charlson Comorbidity Index did not show any notable influence on AFB/fungal positivity rates.

CONCLUSION

These results suggest utility in obtaining routine intraoperative AFB/fungal cultures, given the relatively high positivity and poor predictive factors.

Low Body Mass Index Patients Undergoing an Anterior Lumbar Fusion May Have an Increased Risk of Perioperative Complications

BACKGROUND

Previous research has shown that underweight patients may be at a greater risk of experiencing postsurgical complications. The purpose of this study was to investigate the association between body mass index (BMI) and postoperative complications following single-level anterior lumbar fusion (ALF).

METHODS

All single-level elective ALF procedures performed between 2010 and 2020 were identified in the PearlDiver Mariner Database. Patients were separated into 6 groups based on the World Health Organization BMI classifications. Differences in postsurgical complications (ie, deep vein thrombosis, pulmonary embolism, surgical site infection, hardware malfunction, wound dehiscence, and blood transfusion) among BMI categories were assessed using a χ2 contingency test.

RESULTS

Results indicated that underweight patients (BMI <20) were at a significantly greater risk of developing deep vein thromboses, experiencing hardware malfunction, and requiring blood transfusion compared with any other BMI classification (P < 0.001). Results also demonstrated that underweight individuals had similar risks of developing surgical site infection and wound dehiscence compared with patients classified as having obesity class III.

CONCLUSION

Underweight patients may be at a greater risk than currently believed of experiencing postoperative complications following single-level ALF procedures.

CLINICAL RELEVANCE

Patients with a BMI of 20 or less should be carefully evaluated prior to surgical intervention to ensure they are optimized for surgery.

LEVEL OF EVIDENCE: 3

Body Mass Index and Revision Total Knee Arthroplasty: Does Cause for Revision Vary by Underweight or Obese Status?

BACKGROUND

Body mass index (BMI) impacts risk for revision total knee arthroplasty (rTKA), but the relationship between BMI and cause for revision remains unclear. We hypothesized that patients in different BMI classes would have disparate risk for causes of rTKA.

METHODS

There were 171,856 patients who underwent rTKA from 2006 to 2020 from a national database. Patients were classified as underweight (BMI < 19), normal-weight, overweight/obese (BMI 25 to 39.9), or morbidly obese (BMI > 40). Multivariable logistic regressions adjusted for age, sex, race/ethnicity, socioeconomic status, payer status, hospital geographic setting, and comorbidities were used to examine the effect of BMI on risk for different rTKA causes.

RESULTS

Compared to normal-weight controls, underweight patients were 62% less likely to undergo revision due to aseptic loosening, 40% less likely due to mechanical complications, 187% more likely due to periprosthetic fracture, 135% more likely due to periprosthetic joint infection (PJI). Overweight/obese patients were 25% more likely to undergo revision due to aseptic loosening, 9% more likely due to mechanical complications, 17% less likely due to periprosthetic fracture, and 24% less likely due to PJI. Morbidly obese patients were 20% more likely to undergo revision due to aseptic loosening, 5% more likely due to mechanical complications, and 6% less likely due to PJI.

CONCLUSION

Mechanical reasons were more likely to be the cause of rTKA in overweight/obese and morbidly obese patients, compared to underweight patients, for whom revision was more likely to be infection or fracture related. Increased awareness of these differences may promote patient-specific management to reduce complications.

LEVEL OF EVIDENCE

III.

Underweight Patients are at Increased Risk for Complications following Total Hip Arthroplasty

BACKGROUND

Given the prevalence of obesity in the United States, much of the adult reconstruction literature focuses on the effects of obesity and morbid obesity. However, there is little published data on the effect of being underweight on postoperative outcomes. This study aimed to examine the risk of low body mass index (BMI) on complications after total hip arthroplasty (THA).

METHODS

A large national database was queried between 2010 and 2020 to identify patients who had THAs. Using International Classification of Disease codes, patients were grouped into the following BMI categories: morbid obesity (BMI>40), obesity (BMI 30 to 40), normal BMI (BMI 20 to 30), and underweight (BMI<20). There were 58,151 patients identified, including 2,484 (4.27%) underweight patients, 34,710 (59.69%) obese patients, and 20,957 (36.04%) morbidly obese patients. Control groups were created for each study group, matching for age, sex, and a comorbidity index. Complications that occurred within 1 year postoperatively were isolated. Subanalyses were performed to compare complications between underweight and obese patients. Statistical analyses were performed using Pearson Chi-squares.

RESULTS

Compared to their matched control group, underweight patients showed increased odds of THA revision (Odds Ratio (OR) = 1.32, P = .04), sepsis (OR = 1.51, P = .01), and periprosthetic fractures (OR = 1.63, P = .01). When directly comparing underweight and obese patients (BMI 30 and above), underweight patients had higher odds of aseptic loosening (OR = 1.62, P = .03), sepsis (OR = 1.34, P = .03), dislocation (OR = 1.84, P < .001), and periprosthetic fracture (OR = 1.46, P = .01).

CONCLUSION

Morbidly obese patients experience the highest odds of complications, although underweight patients also had elevated odds for several complications. Underweight patients are an under-recognized and understudied high risk arthroplasty cohort and further research is needed.

Impact of being underweight on peri-operative and post-operative outcomes of total knee or hip arthroplasty: A meta-analysis

BACKGROUND

Many systematic reviews have focused on assessing the effect of body mass index (BMI) on the outcomes and complications associated with total hip arthroplasty (THA) and total knee arthroplasty (TKA), but primarily dealt with obesity compared to normal weight (NW). None of these reviews attempted to assess the effect of low BMI or underweight (UW) compared to NW in patients undergoing THA or TKA.

AIM

This review aims to compare specific operative outcomes such as operation duration, length of hospital stay, and post-operative complications including mortality, infections, deep vein thrombosis, etc. along with re-hospitalization and reoperation rates between UW and NW patients undergoing THA, TKA or both.

METHODS

An electronic search was performed in PubMed, Scopus, Excerpta Medica database (EMBASE), Web of Science (WoS), and Cochrane Central Register of Controlled Trials (CENTRAL) along with a manual search. The quality of the studies was assessed using the Newcastle-Ottawa scale for cohort studies. The data were subjected to both qualitative and quantitative analysis.

RESULTS

Thirteen retrospective and five prospective cohort studies were included. The quality of included studies was assessed to be good to fair. The length of hospital stay after TKA or THA was found to be significantly higher for UW patients when compared to NW patients, with a mean difference: 0.39 95%CI: [0.06, 0.72], P = 0.02 (in days). Studies presenting both THA and TKA together as total joint arthroplasty showed an increased incidence of mortality in patients treated with THA or TKA alone, Odds ratio: 4.18 95%CI: [2.88, 6.07]. A higher incidence of post-operative complications was also observed in UW patients undergoing THA.

CONCLUSION

UW patients undergoing THA or TKA had a higher incidence of post-operative complications and were associated with a higher readmission rate. Moreover, UW patients were associated with an increased incidence of mortality in the studies that reported THA and TKA together.

Underweight patients are the highest risk body mass index group for perioperative adverse events following stand-alone anterior lumbar interbody fusion

BACKGROUND CONTEXT

Prior studies investigating the association between Body Mass Index (BMI) and patient outcomes following spine surgery have had inconsistent conclusions, likely owing to insufficient power, confounding variables, and varying definitions and cutoffs for BMI categories (eg, underweight, overweight, obese, etc.). Further, few studies have considered outcomes among low BMI cohorts.

PURPOSE

The current study analyzes how anterior lumbar interbody fusion (ALIF) perioperative outcomes vary along the BMI spectrum, using World Health Organization (WHO) categories of BMI.

STUDY DESIGN/SETTING

A retrospective cohort study.

PATIENT SAMPLE

Patients undergoing stand-alone one or two-level anterior lumbar interbody fusion (ALIF) found in the 2005-2018 American College of Surgeons National Surgical Quality Improvement Program (NSQIP) databases.

OUTCOME MEASURES

Thirty-day adverse events, hospital readmissions, post-operative infections, and mortality.

METHODS

Stand-alone one or two-level ALIF surgical cases were identified and extracted from the 2005-2018 National Surgical Quality Improvement Program (NSQIP) database. Posterior cases and those primary diagnoses of trauma, tumor, infection, or emergency presentation were excluded. Patients were then binned into WHO guidelines of BMI. The incidence of adverse outcomes within 30-day post-operation was defined. Odds ratios of adverse outcomes, normalized to the average risk of normal-weight subjects (BMI 18.5-24.9 kg/m³), were calculated. Multivariate analysis was then performed controlling for patient factors.

RESULTS

In total, 13,710 ALIF patients were included in the study. Incidence of adverse events was elevated in both the underweight (BMI<18.5 kg/m³) and super morbidly obese (>50 kg/m³), however, multivariate risks for adverse events and postoperative infection were elevated for underweight patients beyond those found in any other BMI category. No effect was noted in these identical variables between normal, overweight, obese class 1, or even obese class 2 patients. Multivariate analysis also found overweight patients to show a slightly protective trend against mortality while the super morbidly obese had elevated odds.

CONCLUSIONS

Underweight patients are at greater odds of experiencing postoperative adverse events than normal, overweight, obese class 1, or even obese class 2 patients. The present study identifies underweight patients as an at-risk population that should be given additional consideration by health systems and physicians, as is already done for those on the other side of the BMI spectrum.

Transfusion Trends of Knee Arthroplasty in Korea: A Nationwide Study Using the Korean National Health Insurance Service Sample Data

Knee arthroplasties are strongly associated with blood transfusion to compensate for perioperative bleeding. The purpose of this study was to evaluate trends of transfusion associated with knee arthroplasties using nationwide data of the National Health Insurance Service-National Sample Cohort (NHIS-NSC). Using data from the nationwide claims database of the Health Insurance Review Assessment Service managed by the NHIS, 50,553 knee arthroplasties under three categories (total knee replacement arthroplasty, uni-knee replacement arthroplasty, and revision arthroplasty) from 2012 to 2018 were identified. Overall transfusion rate, transfusion count, proportion of each type of transfusion, and cost associated with each type of operation were investigated. Overall transfusion rate was 83.4% (5897/7066) in 2012, 82.7% (5793/7001) in 2013, 79.6% (5557/6978) in 2014, 75.9% (5742/7557) in 2015, 73.1% (6095/8337) in 2016, 68.2% (4187/6139) in 2017, and 64.6% (4271/6613) in 2018. The proportion of each type of transfusion was 1.8% for fresh frozen plasma, 0.5% for platelets, and 97.7% for red blood cells. The average cost of transfusion was $109.1 ($123 in 2012, $124 in 2013, $123.3 in 2014, $110.6 in 2015, $100 in 2016, $92.9 in 2017, and $90.1 in 2018). In this nationally representative study of trends in transfusion associated with knee arthroplasty, we observed significantly high rates of blood transfusion among patients undergoing knee arthroplasties. Although the overall rate of transfusion had declined, the allogeneic transfusion rate was still high from 2012 to 2018 in Korea. Thus, surgeons need to develop various patient blood management plans and minimize the use of allogeneic transfusion when performing knee arthroplasties.

Body fat prediction through feature extraction based on anthropometric and laboratory measurements

Obesity, associated with having excess body fat, is a critical public health problem that can cause serious diseases. Although a range of techniques for body fat estimation have been developed to assess obesity, these typically involve high-cost tests requiring special equipment. Thus, the accurate prediction of body fat percentage based on easily accessed body measurements is important for assessing obesity and its related diseases. By considering the characteristics of different features (e.g. body measurements), this study investigates the effectiveness of feature extraction for body fat prediction. It evaluates the performance of three feature extraction approaches by comparing four well-known prediction models. Experimental results based on two real-world body fat datasets show that the prediction models perform better on incorporating feature extraction for body fat prediction, in terms of the mean absolute error, standard deviation, root mean square error and robustness. These results confirm that feature extraction is an effective pre-processing step for predicting body fat. In addition, statistical analysis confirms that feature extraction significantly improves the performance of prediction methods. Moreover, the increase in the number of extracted features results in further, albeit slight, improvements to the prediction models. The findings of this study provide a baseline for future research in related areas.

Caution, "normal" BMI: health risks associated with potentially masked individual underweight-EPMA Position Paper 2021

An increasing interest in a healthy lifestyle raises questions about optimal body weight. Evidently, it should be clearly discriminated between the standardised "normal" body weight and individually optimal weight. To this end, the basic principle of personalised medicine "one size does not fit all" has to be applied. Contextually, "normal" but e.g. borderline body mass index might be optimal for one person but apparently suboptimal for another one strongly depending on the individual genetic predisposition, geographic origin, cultural and nutritional habits and relevant lifestyle parameters-all included into comprehensive individual patient profile. Even if only slightly deviant, both overweight and underweight are acknowledged risk factors for a shifted metabolism which, if being not optimised, may strongly contribute to the development and progression of severe pathologies. Development of innovative screening programmes is essential to promote population health by application of health risks assessment, individualised patient profiling and multi-parametric analysis, further used for cost-effective targeted prevention and treatments tailored to the person. The following healthcare areas are considered to be potentially strongly benefiting from the above proposed measures: suboptimal health conditions, sports medicine, stress overload and associated complications, planned pregnancies, periodontal health and dentistry, sleep medicine, eye health and disorders, inflammatory disorders, healing and pain management, metabolic disorders, cardiovascular disease, cancers, psychiatric and neurologic disorders, stroke of known and unknown aetiology, improved individual and population outcomes under pandemic conditions such as COVID-19. In a long-term way, a significantly improved healthcare economy is one of benefits of the proposed paradigm shift from reactive to Predictive, Preventive and Personalised Medicine (PPPM/3PM). A tight collaboration between all stakeholders including scientific community, healthcare givers, patient organisations, policy-makers and educators is essential for the smooth implementation of 3PM concepts in daily practice.

Risk Adjustment for Episode-of-Care Costs After Total Joint Arthroplasty: What is the Additional Cost of Individual Comorbidities and Demographics?

INTRODUCTION

Concerns exist regarding the lack of risk adjustment in alternative payment models for patients who may use more resources in an episode of care. The purpose of this study was to quantify the additional costs associated with individual medical comorbidities and demographic variables.

METHODS

We reviewed a consecutive series of primary total hip and knee arthroplasty patients at our institution from 2015 to 2016 using claims data from Medicare and a single private insurer. We collected demographic data and medical comorbidities for all patients. To control for confounding variables, we performed a stepwise multivariate regression to determine the independent effect of medical comorbidities and demographics on 90-day episode-of-care costs.

RESULTS

Six thousand five hundred thirty-seven consecutive patients were identified (4,835 Medicare and 1,702 private payer patients). The mean 90-day episode-of-care cost for Medicare and private payers was $19,555 and $30,020, respectively. Among Medicare patients, comorbidities that significantly increased episode-of-care costs included heart failure ($3,937, P < 0.001), stroke ($2,604, P = 0.002), renal disease ($2,479, P = 0.004), and diabetes ($1,368, P = 0.002). Demographics that significantly increased costs included age ($221 per year, P < 0.001), body mass index (BMI; $106 per point, P < 0.001), and unmarried marital status ($1896, P < 0.001). Among private payer patients, cardiac disease ($4,765, P = 0.001), BMI ($149 per point, P = 0.004) and age ($119 per year, P = 0.002) were associated with increased costs.

DISCUSSION

Providers participating in alternative payment models should be aware of factors (cardiac history, age, and elevated BMI) associated with increased costs. Further study is needed to determine whether risk adjustment in alternative payment models can prevent problems with access to care for these high-risk patients.

Low Body Mass Index Is a Predictor for Mortality and Increased Length of Stay Following Total Joint Arthroplasty

BACKGROUND

Malnutrition is a devastating condition which disproportionally affects the elderly population. Malnutrition furthers the pre-existing elevated risk for osteoarthritis in this population, thus exacerbating joint damage in patients and furthering the need for total joint arthroplasty (TJA). A marker for malnutrition is a low body mass index (BMI). The purpose of this study is to investigate whether low BMI status increased the risk for 2-year mortality or reoperation, 90-day readmission, or extended length of stay (LOS) following TJA.

METHODS

A retrospective study was performed using the Partners Arthroplasty Registry which contains data from 2016 to 2019. The registry was queried for primary total hip and primary total knee arthroplasty (TKA) patients that had a minimum of 2-years follow-up data. Demographic, surgical, and clinical outcome variables were obtained from these patients. The association between underweight BMI and objective outcomes of reoperation, 90-day readmission, mortality, and LOS was evaluated by univariate analysis followed by multiple logistic and linear regression analyses.

RESULTS

The final cohort used for analysis consisted of 4802 TJA cases. After accounting for potential confounders, underweight BMI was found to be independently associated with increased risk of mortality within 2 years following TJA (odds ratio 8.77) (95% confidence interval 2.14-32.0) and increased LOS of 0.44 days (95% confidence interval 0.02-0.86).

CONCLUSION

Our findings demonstrate that TJA patients with an underweight BMI experience an 8 times increased risk of 2-year mortality and an increased LOS of 0.44 days. Orthopedic surgeons should consider nutritional consultation and medical optimization in these high-risk patients prior to surgery.

The Effectiveness and Safety of General and Spinal Anesthesia on Systemic Inflammatory Response in Patients with Tumor-Type Total Knee Arthroplasty

BACKGROUND

The anesthesia procedure in tumor-type total knee arthroplasty (TKA) may contribute to systemic inflammatory response. Therefore, we aim to investigate the effectiveness and safety of general and spinal anesthesia in patients with tumor-type TKA.

PATIENTS AND METHODS

Twenty-five patients with tumors around the knee undergoing primary unilateral TKA were randomly divided into the general anesthesia group (n = 13) and spinal anesthesia group (n = 12). Knee joint HSS scores and Western Ontario and McMaster University osteoarthritis index (WOMAC osteoarthritis) were recorded before surgery and 12 months after surgery. Visual analogue scale, C-reactive protein (CPR), tumor necrosis factor-α (TNF-α), and interleukin-8 (IL-8) concentration were measured preoperatively (T0), on the day of the operation (T1), and on the first day (T2) after the operation. Complications in the two groups were recorded.

RESULTS

The operative time, intraoperative blood loss, postoperative drainage, tourniquet time, and complication rate were not significantly different between the general anesthesia and spinal anesthesia groups (all p > 0.05). There were no significant differences in CPR (7.6 ± 3.1, 8.1 ± 4.1, 91.3 ± 24.2 vs. 7.1 ± 2.9, 7.6 ± 3.8, 85.1 ± 19.3 pg/mL, respectively), IL-8 (12.2 ± 6.6, 13.4 ± 7.3, 19.2 ± 10.5 vs. 11.9 ± 5.7, 12.9 ± 8.6, 22.2 ± 12.4 pg/mL, respectively), and TNF-α (2.5 ± 1.7, 2.2 ± 1.9, 2.8 ± 2.1 vs. 2.4 ± 1.3, 2.7 ± 2.1, 2.9 ± 1.6 pg/mL, respectively) between the two groups at T0, T1, and T2 (all p > 0.05). There were no statistical differences in pre- and postoperative HSS knee scores (39.78 ± 11.3, 90.24 ± 15.3 vs. 42.68 ± 12.5, 91.21 ± 16.3) and WOMAC indexes (49.89 ± 7.9, 25.12 ± 6.2 vs. 51.3 ± 8.3, 23.15 ± 5.3) between the two groups (p > 0.05).

CONCLUSION

General anesthesia and spinal anesthesia in patients with tumor-type TKA had the same effectiveness and safety.

Low Body Mass Index and Low Intelligence Quotient Are Infection Risk Factors in Vagus Nerve Stimulation

BACKGROUND

Risk factors for infection after vagus nerve stimulation (VNS) device implantation represent an important issue but remain unclear. We hypothesized that specific risk factors for infection would be associated with VNS device implantation. This study reviewed patients with epilepsy who underwent VNS device implantation and undertook a statistical analysis of risk factors for surgical site infection (SSI).

METHODS

We reviewed all medical records for patients who underwent VNS therapy in our facility between August 2011 and May 2018. Age, sex, height, body weight, body mass index (BMI), intelligence quotient (IQ), surgical incision opening time, blood loss, epilepsy classification, activities of daily living, and generator replacement were statistically compared between cases with and without SSI.

RESULTS

We performed 208 VNS device implantation surgeries at our facility during the study period. Among these, 150 patients underwent initial implantation, 56 patients underwent first generator replacement, and 2 patients underwent second replacement. Six patients (2.7%) with initial implantation and 3 patients (5.4%) with first replacement showed SSI. Low BMI was a risk factor for infection at initial implantation (P < 0.0012) using a BMI within 1.78 kg/m² of the cutoff for being underweight (100% sensitivity, 25% specificity). Low IQ (P = 0.0015) was also a risk factor for SSI.

CONCLUSIONS

This study identified low BMI and low IQ at initial implantation as risk factors for infection.

Transfusion trends in hip arthroplasty in Korea: a nationwide study by the Korean National Health Insurance Service

BACKGROUND

Hip arthroplasties are strongly associated with blood transfusion to compensate for perioperative bleeding. The purpose of this study was to evaluate the trends in transfusion associated with hip arthroplasties, using nationwide data supplied by the National Health Insurance Service.

STUDY DESIGN AND METHODS

We used data from nationwide claims database of the Health Insurance Review Assessment Service. The data managed by the National Health Insurance Service were used to identify 161,934 hip arthroplasties under three categories, including bipolar hemiarthroplasty, total hip arthroplasty, and revision arthroplasty, from 2007 to 2015. The transfusion rates, transfusion amounts, the proportion of transfusion, and cost associated with each type of operation were investigated and stratified according to age, sex, hospital type, and region.

RESULTS

The proportion of patients receiving any allogeneic transfusion was 81.1% in 9 years. The overall proportion of transfusion was 7% fresh frozen plasma, 12% platelets, and 77% RBCs. The average count of transfusions was 4.1 in bipolar hemiarthroplasty (343,815/83,729), 4.3 in total hip arthroplasty (196,869/46,097), and 8.7 in revision arthroplasty (35,044/4,024) from 2007 to 2015.

CONCLUSION

In this nationally representative study of trends in transfusion associated with hip arthroplasty, we observed significantly high rates of blood transfusion among patients undergoing hip arthroplasties. Although the overall amount of transfusion declined, the allogeneic transfusion rate was still high from 2007 to 2015 in Korea, and higher than other countries are reporting.

The association of under-weight and obesity with mortality after hip arthroplasty

Background

although many studies have demonstrated the association between body mass index (BMI) and many diseases, there is little evidence of postoperative mortality after hip arthroplasty. The aim of this study was to evaluate the association between BMI and mortality after hip arthroplasty in the older population.

Methods

a total of 3,627 older patients who underwent hip arthroplasty from 2010 to 2013 were included. We used Cox regression analysis to evaluate the association between BMI and mortality after hip arthroplasty. The hazard ratios (HRs) was calculated from 30 days, 31-365 days, and from the first day of surgery to the day of death during the study.

Results

under-weight (BMI under 18.5 kg/m2) is significantly associated with increased mortality (HR:1.423; 95% Confidence Interval (CI): 1.023-1.981) after hip arthroplasty compared to the normal range. However, in the short-term mortality within 30 days after surgery, both under-weight (HR: 2.368; 95%CI: 1.130-4.960) and obesity (25-29.9 kg/m2, HR: 2.023; 95%CI: 1.008-4.059) are associated with increased mortality.

Conclusion

our study suggested that under-weight is associated with increased risk of mortality after hip arthroplasty. Further, in a short-term outcome, obesity appear to be associated with increased mortality after hip arthroplasty within 30 days.

Cefazolin Prophylaxis for Total Joint Arthroplasty: Obese Patients Are Frequently Underdosed and at Increased Risk of Periprosthetic Joint Infection

BACKGROUND

One of the most effective prophylactic strategies against periprosthetic joint infection (PJI) is administration of perioperative antibiotics. Many orthopedic surgeons are unaware of the weight-based dosing protocol for cefazolin. This study aimed at elucidating what proportion of patients receiving cefazolin prophylaxis are underdosed and whether this increases the risk of PJI.

METHODS

A retrospective study of 17,393 primary total joint arthroplasties receiving cefazolin as perioperative prophylaxis from 2005 to 2017 was performed. Patients were stratified into 2 groups (underdosed and adequately dosed) based on patient weight and antibiotic dosage. Patients who developed PJI within 1 year following index procedure were identified. A bivariate and multiple logistic regression analyses were performed to control for potential confounders and identify risk factors for PJI.

RESULTS

The majority of patients weighing greater than 120 kg (95.9%, 944/984) were underdosed. Underdosed patients had a higher rate of PJI at 1 year compared with adequately dosed patients (1.51% vs 0.86%, P = .002). Patients weighing greater than 120 kg had higher 1-year PJI rate than patients weighing less than 120 kg (3.25% vs 0.83%, P < .001). Patients who were underdosed (odds ratio, 1.665; P = .006) with greater comorbidities (odds ratio, 1.259; P < .001) were more likely to develop PJI at 1 year.

CONCLUSION

Cefazolin underdosing is common, especially for patients weighing more than 120 kg. Our study reports that underdosed patients were more likely to develop PJI. Orthopedic surgeons should pay attention to the weight-based dosing of antibiotics in the perioperative period to avoid increasing risk of PJI.

Weighing in on Body Mass Index and Infection After Total Joint Arthroplasty: Is There Evidence for a Body Mass Index Threshold?

BACKGROUND

Although morbid obesity is considered a modifiable risk factor for periprosthetic joint infection (PJI), there is no consensus regarding an appropriate threshold for body mass index (BMI) above which a high risk for infection may outweigh the benefits of surgery.

QUESTIONS/PURPOSES

(1) Is there a BMI cutoff threshold that is associated with increased risk for PJI? (2) Is the risk of PJI increased in higher obesity classes?

METHODS

A retrospective study was conducted of all primary THAs and TKAs performed at one institution between 2006 and 2015. Overall 19,226 patients were eligible to be included in the study; 1053 patients were excluded as a result of incomplete data, resulting in a final cohort of 18,173 patients (8757 TKAs and 9416 THAs). PJI was defined using the International Consensus Meeting criteria. To ensure accurate followup, and because there is evidence to support the association between obesity and early infection, we identified PJI within 90 days of the index surgery. This relationship was examined separately for BMI as a continuous variable and for each BMI category as defined by the Centers for Disease Control and Prevention (underweight ≤ 18.49 kg/m; normal 18.5-24.9 kg/m; overweight 25-29.9 kg/m; obese class I 30-34.9 kg/m; obese class II 35-39.9 kg/m; obese class III ≥ 40 kg/m). Analyses were performed with logistic regression, accounting for both patient and surgical risk factors. A BMI threshold was evaluated with a receiver operating characteristic (ROC) curve and the Youden index.

RESULTS

The area under the ROC curve for BMI and risk of PJI within 90 days was only 0.58 (confidence interval [CI], 0.52-0.63) suggesting such a cutoff was not much better than random chance. Among the BMI classes, patients with class III obesity (≥ 40 kg/m) were the only ones showing a higher risk for PJI within 90 days (odds ratio [OR], 3.09 [1.46-6.54]; p = 0.003). The risk of developing PJI was not greater for overweight (OR, 0.72; 95% CI, 0.38-1.4), class I obese (OR, 1.06; 95% CI, 0.57-2.0), or class II obese (OR, 1.08; 95% CI, 0.52-2.2) patients. Underweight patients also demonstrated no increased risk for PJI (OR, 1.80; 95% CI, 0.23-13.9).

CONCLUSIONS

The risk for infection increases gradually throughout the full range of BMI, but no threshold exists. Weight reduction before surgery may mitigate risk for infection for all patients with a BMI above normal. Of note, patients with a BMI > 40 kg/m carried a threefold higher risk for PJI and for these patients, the risks of surgery must be carefully weighed against its benefits.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Postoperative complications in underweight patients undergoing total hip arthroplasty: A comparative analysis to normal weight patients

Background

Underweight patients undergoing total hip arthroplasty have been largely overlooked. The purpose of this study was to evaluate their complications profiles compared to normal weight individuals.

Methods

Patients were selected from the NSQIP database, matched, and arranged into 2 groups based on BMI. Complications were recorded and analyzed to determine differences in outcomes.

Results

Multivariate analysis demonstrated increased length of hospital stay (LOS) (p = 0.006) for underweight patients but failed to demonstrate higher rates of medical or surgical complications.

Conclusion

There are no increased rates of infectious or medical complications in underweight patients undergoing THA. However, increased LOS was demonstrated.

Vancomycin Prophylaxis for Total Joint Arthroplasty: Incorrectly Dosed and Has a Higher Rate of Periprosthetic Infection Than Cefazolin

BACKGROUND

In total joint arthroplasty (TJA), vancomycin is used as perioperative antibiotic prophylaxis in patients with penicillin allergy or in patients colonized with methicillin-resistant Staphylococcus aureus (MRSA). Although vancomycin dosing should be weight-based (15 mg/kg), not all surgeons are aware of this; a fixed 1-g dose is instead frequently administered.

QUESTIONS/PURPOSES

(1) Is there a difference in the risk of periprosthetic joint infection (PJI) in patients receiving vancomycin or cefazolin prophylaxis after primary TJA? (2) What proportion of patients is adequately dosed with vancomycin? (3) Compared with actual fixed dosing, does weight-based dosing result in a greater proportion of patients staying above the recommended 15-mg/L level at the beginning and end of surgery? (4) Are patients overdosed with vancomycin at greater risk of developing nephrotoxicity and acute kidney injury?

METHODS

A single-institution, retrospective study was performed on 1828 patients undergoing primary TJAs who received vancomycin prophylaxis between 2008 and 2014. During the same period, 5810 patients underwent primary TJA and received cefazolin monotherapy. A chart review was performed to obtain patient characteristics, antibiotic dose and timing of administration, and microbiology data. Adequate vancomycin dosing was defined as 15 mg/kg and within the 125-mg range. Vancomycin levels were calculated at the beginning and end of surgery using pharmacokinetic equations. Levels of 15 mg/L were considered adequate. Logistic regression, chi square tests, and analysis of variance were performed.

RESULTS

Among primary TJAs, patients receiving vancomycin had a higher rate of PJI (32 of 1828 [2%]) compared with patients receiving cefazolin prophylaxis (62 of 5810 [1%]; adjusted odds ratio, 1.587 [1.004-2.508]; p = 0.048). Ten percent of PJIs in the vancomycin underdosed group (two of 20) was caused by MRSA, and no patients with adequate dosing or overdosing of vancomycin developed PJI with MRSA. Of all procedures in which vancomycin monotherapy was used, 28% (518 of 1828) was adequately dosed according to weight-based dosage recommendations. Furthermore, 94% (1726 of 1828) of patients received a fixed 1-g dose of vancomycin, of whom 64% (1105 of 1726) were underdosed. All patients had vancomycin infusion initiated within 2 hours before incision. A weight-based protocol would have resulted in fewer patients having unacceptably low vancomycin levels (< 15 mg/L) compared with those with actual fixed dosing, both for the beginning of surgery at the time of incision (zero of 1828 [0%] versus 471 of 1828 [26%]; odds ratio, 0.001 [0.000-0.013]; p < 0.001) and at the end of surgery (33 of 1828 [2%] versus 746 of 1828 [41%]; odds ratio, 0.027 [0.019-0.038]; p < 0.001). Between the vancomycin dosage groups, there were no differences in the rate of nephrotoxicity (underdosed: 12 of 1130 [1%], adequately dosed: five of 518 [1%], overdosed: four of 180 [2%], p = 0.363) and acute kidney injury (underdosed: 28 of 1130 [2%], adequately dosed: 10 of 518 [2%], overdosed: six of 180 [3%], p = 0.561).

CONCLUSIONS

The majority of patients given vancomycin prophylaxis are underdosed according to the weight-based dosage recommendations, and MRSA did not occur in patients who were adequately dosed with vancomycin. Surgeons should thus ensure that their patients are adequately dosed with vancomycin using the recommendation of 15 mg/kg and that the dose of vancomycin is administered in a timely fashion. Furthermore, and based on the findings of this study, we have moved toward limiting the utilization of vancomycin prophylaxis for patients undergoing elective arthroplasty at our institution.

LEVEL OF EVIDENCE

Level III, therapeutic study.