Are We Winning or Losing the Battle With Periprosthetic Joint Infection: Trends in Periprosthetic Joint Infection and Mortality Risk for the Medicare Population.

BACKGROUND: Periprosthetic joint infection (PJI) is a potentially deadly complication of total joint arthroplasty. This study was designed to address how the incidence of PJI and outcome of treatment, including mortality, are changing in the population over time. METHODS: Primary total hip arthroplasty (THA) and total knee arthroplasty (TKA) patients with PJI from the 100% Medicare inpatient data set (2005-2015) were identified. Cox proportional hazards regression models for risk of PJI after THA/TKA (accounting for competing risks) or risk of all-cause mortality after PJI were adjusted for patient and clinical factors, with year included as a covariate to test for time trends. RESULTS: The unadjusted 1-year and 5-year risk of PJI was 0.69% and 1.09% for THA and 0.74% and 1.38% for TKA, respectively. After adjustment, PJI risk did not change significantly by year for THA (P = .63) or TKA (P = .96). The unadjusted 1-year and 5-year overall survival after PJI diagnosis was 88.7% and 67.2% for THA and 91.7% and 71.7% for TKA, respectively. After adjustment, the risk of mortality after PJI decreased significantly by year for THA (hazard ratio = 0.97; P < .001) and TKA (hazard ratio = 0.97; P < .001). CONCLUSION: Despite recent clinical focus on preventing PJI, we are unable to detect substantial decline in the risk of PJI over time, although mortality after PJI has declined. Because PJI risk appears not to be changing over time, the incidence of PJI is anticipated to scale up proportionately with the demand for THA and TKA, which is projected to increase substantially in the coming decade.

What Are the Frequency, Associated Factors, and Mortality of Amputation and Arthrodesis After a Failed Infected TKA?

BACKGROUND: For patients with failed surgical treatment of an infected TKA, salvage operations such as arthrodesis or above-knee amputation (AKA) may be considered. Clinical and institutional factors associated with AKA and arthrodesis after a failed TKA have not been investigated in a large-scale population, and the utilization rate and trend of these measures are not well known. QUESTIONS/PURPOSES: (1) How has the frequency of arthrodesis and AKA after infected TKA changed over the last 10 years? (2) What clinical or institutional factors are associated with patients undergoing arthrodesis or AKA? (3) What is the risk of mortality after arthrodesis or AKA? METHODS: The Medicare 100% National Inpatient Claims Database was used to identify 44,466 patients 65 years of age or older who were diagnosed with an infected TKA and who underwent revision between 2005 and 2014 based on International Classification of Diseases, 9th Revision, Clinical Modification codes. Overall, 1182 knee arthrodeses and 1864 AKAs were identified among the study population. One year of data before the index infection-related knee revision were used to examine patient demographic, institutional, and clinical factors, including comorbidities, hospital volumes, and surgeon volumes. We developed Cox regression models to investigate the risk of arthrodesis, AKA, and death as outcomes. In addition, the year of the index revision was included as a covariate to determine if the risk of subsequent surgical interventions was changing over time. The risk of mortality was also assessed as the event of interest using a similar multivariate Cox model for each patient group (arthrodesis, AKA) in addition to those who underwent additional revisions but who did not undergo either of the salvage procedures. RESULTS: The number of arthrodesis (hazard ratio [HR], 0.90, p < 0.001) and amputation (HR, 0.95, p < 0.001) procedures showed a declining trend. Clinical factors associated with arthrodesis included acute renal failure (HR, 1.22 [1.06-1.41], p = 0.006), obesity (HR, 1.58 [1.35-1.84], p < 0.001), and having additional infection-related revisions (HR for 2+ additional revisions, 1.36 [1.13-1.64], p = 0.001). Higher Charlson comorbidity score (HR for a score of 5+ versus 0, 2.56 [2.12-3.14], p < 0.001), obesity (HR, 1.14 [1.00-1.30], p = 0.044), deep vein thrombosis (HR, 1.34 [1.12-1.60], p = 0.001), and additional revisions (HR for 2+ additional revisions, 2.19 [1.91-2.49], p < 0.001) were factors associated with AKA, which in turn was an independent risk factor for mortality. The risk of death increased with amputation after adjusting for age, comorbidities, and other factors (HR, 1.28 [1.20-1.37], p < 0.001), but patients who received arthrodesis did not show a change in mortality compared with the patients who did not receive arthrodesis or amputation (HR, 1.00 [0.91-1.10], p = 0.971). CONCLUSIONS: The findings of this study suggest that clinicians may be more aggressively attempting to preserve the knee even in the face of chronic prosthetic joint infection but also show that a greater number of revisions is associated with a greater risk of subsequent AKA or arthrodesis. The results also suggest that recommending centers with a high volume of joint arthroplasties may be a way to reduce the risk of the salvage procedures. LEVEL OF EVIDENCE: Level III, therapeutic study.

Surgical Risks and Costs of Care are Greater in Patients Who Are Super Obese and Undergoing THA.

BACKGROUND: Patients with morbid obesity, defined as a BMI greater than 40 kg/m2, and super obesity, defined as a BMI greater than 50 kg/m2, increasingly present for total hip replacement. There is disagreement in the literature whether these individuals have greater surgical risks and costs for the episode of care, and the magnitude of those risks and costs. There also is no established threshold for obesity as defined by BMI in identifying increased complications, risks, and costs of care. Until recently, analysis of higher BMI data was limited to small cohorts from hospital-based data banks, based on BMI or height and weight only, often as part of a multivariate analysis. On October 1, 2010 the Centers for Medicare & Medicaid Services added a fifth digit to the BMI data, V85.xx, in the Medicare data bank, which allowed data mining of cases of patients with higher BMI. To our knowledge, our study is the first large retrospective Medicare data mining study, which allows us to examine BMI levels greater than 40 and 50 kg/m2 to delineate risks, complications, and costs for these patients. QUESTIONS/PURPOSES: We sought to quantify (1) the surgical risk, and (2) the costs associated with complications after THA in patients who were morbidly obesity (BMI ≥ 40 kg/m2) or super obese (BMI ≥ 50 kg/m2). METHODS: This is a retrospective study of patients, using Medicare hospital claims data, who underwent THA. The ICD-9 Clinical Modification (CM) diagnosis code V85.4x was used to identify patients with morbid obesity and with super obesity from October 1, 2010 through December 31, 2014. Patients without any BMI-related diagnosis codes were used as the control group. Twelve complications occurring during the 90 days after THA were analyzed using multivariate Cox models adjusting for patient demographic, comorbidities, and institutional factors. In addition, hospital charges and payments were compared from primary surgery through the subsequent 90 days. RESULTS: Patients with morbid obesity had increased postoperative complications including prosthetic joint infection (hazard ratio [HR], 3.71; 95% CI, 3.2-4.31; p < 0.001), revision (HR, 1.91; 95% CI, 1.69-2.16; p < 0.001), and wound dehiscence (HR, 3.91; 95% CI, 3.14-4.86; p < 0.001). In addition, patients with morbid obesity had increased risk of deep vein thrombosis (HR, 1.43; 95% CI, 1.14-1.79; p < 0.002), pulmonary embolism (HR, 1.57; 95% CI, 1.25-1.99; p < 0.001), implant failure (HR, 1.48; 95% CI, 1.3-1.68; p < 0.001), acute renal failure (HR, 1.68; 95% CI, 1.56-1.80; p < 0.001), and all-cause readmission (HR, 1.48; 95% CI, 1.40-1.56; p < 0.001). However, death (HR, 0.94 95% CI, 0.73-1.19 p < 0.592), acute myocardial infarction (HR, 0.94; 95% CI, 0.74-1.2 p < 0.631), and dislocation (HR 1.07; 95% CI, 0.85-1.34; p < 0.585) were not different between patients in the control and morbidly obese groups. Super obese patients had an increased risk of infection (HR, 6.48; 95% CI, 4.54-9.25; p < 0.001), wound dehiscence (HR, 9.81; 95% CI, 6.31-15.24; p < 0.001), and readmission (HR, 2.16; 95% CI, 1.84-2.54; p < 0.001) compared with patients with normal BMI. Controlling for patient and institutional factors, each THA had mean total hospital charges of USD 88,419 among patients who were super obese compared with USD 73,827 for the control group, a difference of USD 14,591. Medicare payment for the patients who were super obese also was higher, but only by USD 3631. CONCLUSIONS: Patients who are super obese are at increased risk for serious complications compared with patients with morbid obesity, whose risks are elevated relative to patients whose BMI is less than 40 kg/m2. Costs of care for patients who were super obese, likewise, were increased. We present BMI outcomes to allow an objective basis for patient counseling, risk stratification, maintaining access to orthopaedic surgical care, and maintaining hospital operating margins. LEVEL OF EVIDENCE: Level III, therapeutic study.

Risk and Cost of 90-Day Complications in Morbidly and Superobese Patients After Total Knee Arthroplasty.

BACKGROUND: This study investigated the risk and cost of postoperative complications associated with morbid and super obesity after total knee arthroplasty (TKA). METHODS: A retrospective cohort study was conducted of patients who underwent TKA using Medicare hospital claims data. The International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis code V85.4x was used to identify morbidly obese patients (body mass index [BMI] ≥40 kg/m(2)) and superobese patients (BMI ≥50 kg/m(2)) in 2011-2013. Patients without any BMI-related diagnosis codes were used as controls. Twelve complications occurred in the 90-day period after TKA were analyzed using multivariate Cox models, adjusting for patient demographic, morbidity, and institutional factors. In addition, hospital charges and payments were compared from primary surgery through subsequent 90 days. RESULTS: Morbidly obese patients showed a significantly elevated risk in most complications examined, with a 2-fold or higher risk in dislocation and wound dehiscence. In addition, death, periprosthetic joint infection, acute renal failure, and knee revision had significant hazard ratios between 1.5 and 2.0. However, risk of deep vein thrombosis and acute myocardial infarction did not increase for the morbidly obese patients. Superobese patients had significant increase in risk of infection, wound dehiscence, acute renal failures, revisions, death, and readmission compared with patients with BMI 40-49 kg/m(2). Significant dose-response trend was found between the level of BMI and risk for death, dislocation, implant failure, infection, readmission, revision, wound dehiscence, and acute renal failure. Controlling for patient and institutional factors, each TKA had an average total hospital charges of $75,884 among superobese patients, compared to $65,118 for the control group, a difference of $10,767. Medicare payment for the superobese patients was also higher, but only by $2703. CONCLUSION: Morbidly obese patients pose a significantly higher risk profile than normal-weight patients in a broad range of complications after TKA. Superobese patients add another layer of risk compared with less obese patients and are considerably more expensive to treat by health care systems. Technical difficulties and the high demand on resources present a severe challenge for providing treatment for such patients.

The Validity of Administrative BMI Data in Total Joint Arthroplasty.

Identifying BMI via administrative data is a useful way to evaluate outcomes in total joint arthroplasty (TJA) for varying degrees of obesity. The purpose of this study was to evaluate the concordance between BMI coding in administrative claims data and actual clinical BMI measurements in the medical record for patients undergoing TJA. Clinical BMI value was shown to be a significant determinant of whether ICD-9 codes were used to report the patient's obesity status (P<0.01). Although a higher clinical BMI strongly increased the likelihood of having either of the ICD-9 diagnosis codes used to identify obesity status, only the accuracy of the V85 code increased with increasing levels of BMI.

Mechanisms of osteoarthritis in the knee: MR imaging appearance.

Osteoarthritis has grown to become a widely prevalent disease that has major implications in both individual and public health. Although originally considered to be a degenerative disease driven by "wear and tear" of the articular cartilage, recent evidence has led to a consensus that osteoarthritis pathophysiology should be perceived in the context of the entire joint and multiple tissues. MRI is becoming an increasingly more important modality for imaging osteoarthritis, due to its excellent soft tissue contrast and ability to acquire morphological and biochemical data. This review will describe the pathophysiology of osteoarthritis as it is associated with various tissue types, highlight several promising MR imaging techniques for osteoarthritis and illustrate the expected appearance of osteoarthritis with each technique.

Quantitative tracking of passage and 3D culture effects on chondrocyte and fibrochondrocyte gene expression.

Success in cartilage and fibrocartilage tissue engineering relies heavily on using an appropriate cell source. Many different cell sources have been identified, including primary and stem cells, along with experimental strategies to obtain the required number of cells or to induce chondrogenesis. However, no definitive method exists to quantitatively evaluate the similarity of the resulting cell phenotypes to those of the native cells between candidate strategies. In this study, we develop an integrative approach to enable such evaluations by deriving, from gene expression profiles, two quantitative metrics representing the nearest location within the range of native cell phenotypes and the deviation from it. As an example application to evaluating potential cell sources for cartilage or meniscus tissue engineering, we examine phenotypic changes of juvenile and adult articular chondrocytes and fibrochondrocytes across multiple passages and subsequent 3D culture. A substantial change was observed in cell phenotype due to the isolation process itself, followed by a clear progression toward the outer meniscal cell phenotype with passage. The new metrics also indicated that 3D culture moderately reduced the passage-induced deviation from the native meniscal phenotypes for juvenile chondrocytes and adult fibrochondrocytes, which was not obvious through examination of individual gene expressions. However, brief 3D culture alone did not move any of the cells towards an inner meniscal phenotype, the most relevant target for meniscal tissue engineering. This integrative approach of examining and combining multiple gene expressions can be used to evaluate various other tissue-engineering strategies to direct cells toward the desired phenotype. Copyright © 2015 John Wiley & Sons, Ltd.