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Background: The Affordable Care Act of 2010 advanced the economic model of bundled payments for total joint arthroplasty (TJA), in which hospitals will be financially responsible for readmissions, typically at 90 days after surgery. However, little is known about the financial burden of readmissions and what patient, clinical, and hospital factors drive readmission costs., Questions/purposes: (1) What is the incidence, payer mix, and demographics of THA and TKA readmissions in the United States? (2) What patient, clinical, and hospital factors are associated with the cost of 30- and 90-day readmissions after primary THA and TKA? (3) Are there any differences in the economic burden of THA and TKA readmissions between payers? (4) What types of THA and TKA readmissions are most costly to the US hospital system?, Methods: The recently developed Nationwide Readmissions Database from the Healthcare Cost and Utilization Project (2006 hospitals from 21 states) was used to identify 719,394 primary TJAs and 62,493 90-day readmissions in the first 9 months of 2013 based on International Classification of Diseases, 9th Revision, Clinical Modification codes. We classified the reasons for readmissions as either procedure- or medical-related. Cost-to-charge ratios supplied with the Nationwide Readmissions Database were used to compute the individual per-patient cost of 90-day readmissions as a continuous variable in separate general linear models for THA and TKA. Payer, patient, clinical, and hospital factors were treated as covariates. We estimated the national burden of readmissions by payer and by the reason for readmission., Results: The national rates of 30- and 90-day readmissions after THA were 4% (95% confidence interval [CI], 4.2%-4.5%) and 8% (95% CI, 7.5%-8.1%), respectively. The national rates of 30- and 90-day readmissions after primary TKA were 4% (95% CI, 3.8%-4.0%) and 7% (95% CI, 6.8%-7.2%), respectively. The five most important variables responsible for the cost of 90-day THA readmissions (in rank order, based on the Type III F-statistic, p < 0.001) were length of stay (LOS), all patient-refined diagnosis-related group (APR DRG) severity, type of readmission (that is, medical- versus procedure-related), hospital ownership, and age. Likewise, the five most important variables responsible for the cost of 90-day TKA readmissions were LOS, APR DRG severity, gender, hospital procedure volume, and hospital ownership. After adjusting for covariates, mean 90-day readmission costs reimbursed by private insurance were, on average, USD 1324 and USD 1372 greater than Medicare (p < 0.001) for THA and TKA, respectively. In the 90 days after TJA, two-thirds of the total annual readmission costs were covered by Medicare. In 90 days after THA, more readmissions were still associated with procedure-related complications, including infections, dislocations, and periprosthetic fractures, which in aggregate account for 59% (95% CI, 59.1%-59.6%) of the total readmission costs to the US healthcare system. For TKA, 49% of the total readmission cost (95% CI, 48.8%-49.6%) in 90 days for the United States was associated with procedure issues, most notably including infections., Conclusions: Hospital readmissions up to 90 days after TJA represent a massive economic burden on the US healthcare system. Approximately half of the total annual economic burden for readmissions in the United States is medical and unrelated to the joint replacement procedure and half is related to procedural complications., Clinical Relevance: This national study underscores LOS during readmission as a primary cost driver, suggesting that hospitals and doctors further optimize, to the extent possible, the clinical pathways for the hospitalization of readmitted patients. Because patients readmitted as a result of infection, dislocation, and periprosthetic fractures are the most costly types of readmissions, efforts to reduce the LOS for these types of readmissions will have the greatest impact on their economic burden. Additional clinical research is needed to determine the extent to which, if any, the LOS during readmissions can be reduced without sacrificing quality or access of care.

Background: The state of Massachusetts enacted universal health insurance in 2006. However it is unknown whether the increased access to care resulted in changes to surgical use or costs., Questions/purposes: We asked the following related research questions: compared with the United States as a whole, how did the (1) number of cases (as a percentage of the overall population, to account for changes in the overall population during the time surveyed), (2) payer mix, and (3) inpatient costs for arthroplasty change in Massachusetts after introduction of health insurance reform?, Methods: We analyzed the use and cost of primary THAs and TKAs in Massachusetts using the State Inpatient Database (SID) between 2002 and 2011 compared with the Nationwide Inpatient Sample (NIS) during the same years. The SID captures 100% of inpatient procedures in Massachusetts, while the NIS is a nationally representative database of inpatient procedures for the United States. The SID and NIS are publicly available data sources from the Agency for Healthcare Research and Quality, and include information regarding procedure volumes, payer mixes, and costs. Inpatient costs were defined similarly in both databases by using hospital charges and an average cost-to-charge ratio that is unique for each hospital. The incidence of arthroplasties was calculated by dividing the procedure volume by the relevant population (either for Massachusetts or the entire country) based on public data from the United States Census bureau., Results: The incidence of THAs and TKAs performed in Massachusetts increased steadily throughout the study period, and paralleled a similar increase in the United States as a whole. In Massachusetts, the incidence of THAs increased by 59% between 2002 and 2011, and the incidence of TKAs likewise increased by 80%. The trends for the incidence in total joint arthroplasties were similar to those for Massachusetts for the United States as a whole. The period of health insurance reform in Massachusetts was associated with a greater proportion of patients covered by Medicaid, Commonwealth Care, or Health Safety Net for THAs and TKAs. By 2011, universal health insurance in Massachusetts covered 2.45% of primary THAs and 2.77% of primary TKAs. Coverage for Medicaid in Massachusetts increased from 3.23% and 3.04% of THAs and TKAs in 2002 to 4.06% and 4.34% respectively in 2011. On average, Medicaid coverage was greater for TKAs in Massachusetts than across the United States during the study period. The introduction of health insurance reform had a minimal effect on the cost of total joint arthroplasties in Massachusetts. Although the costs of total joint arthroplasties in the United States were higher than those in Massachusetts, this difference narrowed substantially from 2002 to 2011, with the Massachusetts cost trending upward and the overall United States cost trending downward., Conclusions: Despite extending insurance coverage to the entire state of Massachusetts, there was little change in actual utilization trends for joint replacement., Clinical Relevance: The enactment of universal health insurance coverage in Massachusetts appears to have been a nonevent insofar as the use and cost of total hip and knee surgeries is concerned in the state. Factors other than health insurance reform appear to be driving the growth in demand for arthroplasties in Massachusetts and are likely to do so as well in the United States under the Affordable Care Act of 2010.

Background: Revision is technically more demanding than primary total joint arthroplasty (TJA) and requires more extensive use of resources. Understanding the relative risk of rerevision and risk factors can help identify patients at high risk who may require closer postsurgical care., Objectives/purposes: We therefore evaluated the risk of subsequent revision after primary and revision TJA in the elderly (65 years or older) patient population and identified corresponding patient risk factors., Patients and Methods: Using the 5% Medicare claims data set (1997-2006), we identified a total of 35,746 patients undergoing primary THA and 72,913 undergoing primary TKA; of these, 1205 who had THAs and 1599 who had TKAs underwent initial revision surgery. The rerevision rate after primary and revision TJAs was analyzed by the Kaplan-Meier method. The relative risk of revision surgery for primary and revision TJAs was compared using hazard ratio analysis., Results: The 5-year survival probabilities were 95.9%, 97.2%, 81.0%, and 87.4% for primary THA and TKA and revision THA and TKA, respectively. Patients with revision arthroplasty were five to six times more likely to undergo rerevision (adjusted relative risk, 4.89 for THA; 5.71 for TKA) compared with patients with primary arthroplasty. Age and comorbidities were associated with initial revision after primary THA and TKA., Conclusions: Patients should undergo stringent preoperative screening for preexisting health conditions and careful patient management and followup postoperatively so as to minimize the risk of an initial revision, which otherwise could lead to a significantly greater likelihood of subsequent rerevisions.

Unlabelled: The current risk of infection in contemporary total knee arthroplasty (TKA) as well as the relative importance of risk factors remains under debate as a result of the rarity of the complication and temporal changes in the treatment and prevention of infection. We therefore determined infection incidence and risk factors after TKA in the Medicare population. The Medicare 5% national sample administrative data set was used to identify and longitudinally follow patients undergoing TKA for deep infections and revision surgery between 1997 and 2006. Cox regression was used to evaluate patient and hospital characteristics. In 69,663 patients undergoing elective TKA, 1400 TKA infections were identified. Infection incidence within 2 years was 1.55%. The incidence between 2 and up to 10 years was 0.46%. Women had a lower risk of infection than men. Comorbidities also increased TKA infection risk. Patients receiving public assistance for Medicare premiums were at increased risk for periprosthetic joint infection (PJI). Hospital factors did not predict an increased risk of infection. PJI occurs at a relatively high rate in Medicare patients with the greatest risk of PJI within the first 2 years after surgery; however, approximately one-fourth of all PJIs occur after 2 years., Level of Evidence: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Attempts to preserve periacetabular bone stock following total hip replacement have largely ignored the potential for stress shielding in the acetabulum. We sought to quantify the change in stress distribution in acetabular bone with components of varying material stiffness by developing a high-resolution 3-D finite element model from CT scans of a young female donor. Periprosthetic bone stresses and strains on the left pelvis were compared with hemispherical cups of various material properties and with a horseshoe shaped polymeric design described in the recent literature. We observed unphysiologic periacetabular bone stress and strain fields for all designs tested. For hemispherical components, reduction of the acetabular shell material modulus caused modest changes in bone stress compared to the changes in implant geometry. The horseshoe shaped cup more effectively loaded the acetabular structures than the hemispherical design. Our results suggest stress and strain fields in pelvic structures after introduction of hemispherical acetabular components predict inevitable bone adaptation that can not be resolved by changes in implant material properties alone. Radical changes in implant design may be necessary for long-term maintenance of supporting structures in the reconstructed acetabulum.

Unlabelled: The economic burden to Medicare due to revision arthroplasty procedures has not yet been studied systematically. The economic burden of revisions was calculated as annual reimbursements for revision arthroplasties relative to the sum total reimbursements of primary and revision arthroplasties. We evaluated this revision burden for total hip and knee arthroplasties through investigation of trends in charges and reimbursements in the Medicare population (Parts A and B claims from 1997-2003), while taking into account age and gender effects. Mean annual economic revision burdens were 18.8% (range, 17.4-20.2%) and 8.2% (range, 7.5-9.2%) for total hip arthroplasties and total knee arthroplasties, respectively. Procedural charges increased while reimbursements decreased over the study period, with higher charges observed for revisions than primary arthroplasties. Reimbursements per procedure were 62% to 68% less than associated charges for primary and revision total hip and knee arthroplasties. The effect of age and gender on reimbursements varied by procedure type. Unless some limiting mechanism is implemented to reduce the incidence of revision surgeries, the diverging trends in reimbursements and charges for total hip and knee arthroplasties indicate that the economic impact to the Medicare population and healthcare system will continue to increase., Level of Evidence: Prognostic study, level II-1 (retrospective study). See Guidelines for Authors for a complete description of levels of evidence.