Association of Rurality and Neighborhood Level Socioeconomic Deprivation with Perioperative Health Status in Total Joint Arthroplasty Patients: Analysis from a Large, Tertiary Care Hospital.

BACKGROUND: Individual socioeconomic status (SES) is associated with disparities in access to care and worse outcomes in total joint arthroplasty (TJA). Neighborhood-level SES measures are sometimes used as a proxy for individual-level SES, but the validity of this approach is unknown. We examined neighborhood level SES and rurality on perioperative health status in TJA. METHODS: The study population comprised 46,828 TJA surgeries performed at a tertiary care hospital. Community area deprivation index (ADI) was derived from the 2015 American Census Survey. Logistic regression was used to examine perioperative characteristics by ADI and rurality. RESULTS: Compared to patients from the least deprived neighborhoods, patients from the most deprived neighborhoods were likely to be female (odds ratioOR 1.46, 95% confidence interval CI: 1.33-1.61), non-white (OR 1.36, 95% CI: 1.13-1.64), with education high school or less (OR 4.85, 95% CI: 4.35-5.41), be current smokers (OR 2.20, 95% CI: 1.61-2.49), have BMI>30 kg/m2 (OR 1.43, 95% CI: 1.30-1.57), more limitation on instrumental activities of daily living (OR 1.75, 95% CI: 1.55-1.97) and American Society of Anesthesiologists (ASA) score > II (OR 2.0, 95% CI: 1.11-1.37). There was a progressive association between the degree of area level deprivation with preexisting comorbidities. Patients from rural communities were more likely to be male, white, have body mass index (BMI)>30 kg/m2 and lower education levels. However, rurality was either not associated or negatively associated with comorbidities. CONCLUSION: TJA patients from lower SES neighborhoods have worse behavioral risk factors and higher comorbidity burden than patients from higher SES neighborhoods. Patients from rural communities have worse behavioral risk factors but not comorbidities.

Effects of Hospital and Surgeon Volume on Patient Outcomes After Total Joint Arthroplasty: Reported From the American Joint Replacement Registry.

BACKGROUND: The purpose of this study was to evaluate outcomes and complications because it relates to surgeon and hospital volume for patients undergoing primary total hip arthroplasty (THA) and total knee arthroplasty (TKA) using the American Joint Replacement Registry from 2012 to 2017. METHODS: A retrospective study was conducted on Medicare-eligible cases of primary elective THAs and TKAs reported to the American Joint Replacement Registry database and was linked with the available Centers of Medicaid and Medicare Services claims and the National Death Index data from 2012 to 2017. Surgeon and hospital volume were defined separately based on the median annual number of anatomic-specific total arthroplasty procedures performed on patients of any age per surgeon and per hospital. Values were aggregated into separate surgeon and hospital volume tertile groupings and combined to create pairwise comparison surgeon/hospital volume groupings for hip and knee. RESULTS: Adjusted multivariable logistic regression analysis found low surgeon/low hospital volume to have the greatest association with all-cause revisions after THA (odds ratio [OR], 1.63, 95% confidence interval [CI], 1.41-1.89, P < 0.0001) and TKA (OR, 1.72, 95% CI, 1.44-2.06, P < 0.0001), early revisions because of periprosthetic joint infection after THA (OR, 2.50, 95% CI, 1.53-3.15, P < 0.0001) and TKA (OR, 2.18, 95% CI, 1.64-2.89, P < 0.0001), risk of early THA instability and dislocation (OR, 2.47, 95% CI, 1.77-3.46, P < 0.0001), and 90-day mortality after THA (OR, 1.72, 95% CI, 1.27-2.35, P = 0.0005) and TKA (OR, 1.47, 95% CI, 1.15-1.86, P = 0.002). CONCLUSION: Our findings demonstrate considerably greater THA and TKA complications when performed at low-volume hospitals by low-volume surgeons. Given the data from previous literature including this study, a continued push through healthcare policies and healthcare systems is warranted to direct THA and TKA procedures to high-volume centers by high-volume surgeons because of the evident decrease in complications and considerable costs associated with all-cause revisions, periprosthetic joint infection, instability, and 90-day mortality. LEVEL OF EVIDENCE: III.

Migration Patterns for Revision Total Knee Arthroplasty in the United States as Reported in the American Joint Replacement Registry.

BACKGROUND: Revision total knee arthroplasty (TKA) is associated with a higher complication rate and a greater cost when compared to primary TKA. Based on patient choice, referral, or patient transfers, revision TKAs are often performed in different institutions by different surgeons than the primary TKA. The aim of this study is to evaluate the effect of hospital size, teaching status, and revision indication on the migration patterns of failed primary TKA in patients 65 years of age and older. METHODS: All primary and revision TKAs reported to the American Joint Replacement Registry from January 2012 through March 2020 were included and merged with the Centers for Medicare and Medicaid Services database. Migration was defined as a patient having a primary TKA and revision TKA performed at separate institutions by different surgeons. RESULTS: In total, 9167 linked primary and revision TKAs were included in the analysis. Overall migration rates were significantly higher from small (<100 beds; P = .019), non-teaching institutions (P = .002) driven primarily by patients diagnosed with infection. Infection patients had significantly higher migration rates from small (46.8%, P < .001), non-teaching (43.5%, P < .001) institutions, while migration rates for other causes of revision were statistically similar. Most patients migrated to medium or large institutions (84.7%) for revision TKA rather than small institutions (15.3%, P < .001) and to teaching (78.3%) rather than non-teaching institutions (21.7%, P < .001). CONCLUSION: There is a diagnosis-dependent referral bias that affects the migration rates of infected primary TKA from small non-teaching institutions leading to a flow of more medically complex patients to medium and large teaching institutions for infected revision TKA.

Deep Learning Artificial Intelligence Model for Assessment of Hip Dislocation Risk Following Primary Total Hip Arthroplasty From Postoperative Radiographs.

BACKGROUND: Dislocation is a common complication following total hip arthroplasty (THA), and accounts for a high percentage of subsequent revisions. The purpose of this study is to illustrate the potential of a convolutional neural network model to assess the risk of hip dislocation based on postoperative anteroposterior pelvis radiographs. METHODS: We retrospectively evaluated radiographs for a cohort of 13,970 primary THAs with 374 dislocations over 5 years of follow-up. Overall, 1490 radiographs from dislocated and 91,094 from non-dislocated THAs were included in the analysis. A convolutional neural network object detection model (YOLO-V3) was trained to crop the images by centering on the femoral head. A ResNet18 classifier was trained to predict subsequent hip dislocation from the cropped imaging. The ResNet18 classifier was initialized with ImageNet weights and trained using FastAI (V1.0) running on PyTorch. The training was run for 15 epochs using 10-fold cross validation, data oversampling, and augmentation. RESULTS: The hip dislocation classifier achieved the following mean performance (standard deviation): accuracy = 49.5 (4.1%), sensitivity = 89.0 (2.2%), specificity = 48.8 (4.2%), positive predictive value = 3.3 (0.3%), negative predictive value = 99.5 (0.1%), and area under the receiver operating characteristic curve = 76.7 (3.6%). Saliency maps demonstrated that the model placed the greatest emphasis on the femoral head and acetabular component. CONCLUSION: Existing prediction methods fail to identify patients at high risk of dislocation following THA. Our radiographic classifier model has high sensitivity and negative predictive value, and can be combined with clinical risk factor information for rapid assessment of risk for dislocation following THA. The model further suggests radiographic locations which may be important in understanding the etiology of prosthesis dislocation. Importantly, our model is an illustration of the potential of automated imaging artificial intelligence models in orthopedics. LEVEL OF EVIDENCE: Level III.

Migration Patterns for Revision Total Hip Arthroplasty in the United States as Reported in the American Joint Replacement Registry.

BACKGROUND: Revision total hip arthroplasty (revTHA) is associated with higher rates of complications and greater costs than primary procedures. The aim of this study is to evaluate the effect of hospital size, teaching status, and indication for revTHA, on migration patterns in patients older than 65 years old. METHODS: All THAs and revTHAs reported to the American Joint Replacement Registry from 2012 to 2018 were included and merged with the Centers for Medicare and Medicaid Services database. Migration rate was defined as a patient's THA and revTHA procedures that were performed at separate institutions by different surgeons. Migratory patterns were recorded based on hospital size, teaching status, and indication for revTHA. Analyses were performed by statisticians. RESULTS: The number of linked procedures included was 11,906. Migration rates in revTHA due to infection were higher for small hospitals than large hospitals (46.6% vs 28.6%, P < .0001). Migration rates were higher comparing non-teaching with teaching hospitals (55% vs 34%, P < .0001). This difference was significant for periprosthetic fractures (70.6% vs 37.2%, P = .005), instability (56.5% vs 35.5%, P = .04), and mechanical complications (88.9% vs 34.7%, P < .05). Most patients migrated to medium or large hospitals rather than small hospitals (89% vs 11%, P < .0001) and to teaching rather than non-teaching institutions (82% vs 18%, P < .0001). CONCLUSION: Hospital size and teaching status significantly affected migration patterns for revTHA. Migration rates were significantly higher in small non-teaching hospitals in revTHA due to infection, periprosthetic fracture, instability, and mechanical complications. Over 80% of patients migrated to larger teaching hospitals.

Direct Inpatient Medical Costs of Operative Treatment of Periprosthetic Hip and Knee Infections Are Twofold Higher Than Those of Aseptic Revisions.

BACKGROUND: Periprosthetic joint infections (PJIs) following total hip arthroplasty (THA) and total knee arthroplasty (TKA) are associated with substantial morbidity. A better understanding of the costs of PJI treatment can inform prevention, treatment, and reimbursement strategies. The purpose of the present study was to describe direct inpatient medical costs associated with the treatment of hip and knee PJI. METHODS: At a single tertiary care institution, 176 hips and 266 knees that underwent 2-stage revisions for the treatment of PJI from 2009 to 2015 were compared with 1,611 hips and 1,276 knees that underwent revisions for aseptic indications. In addition, 84 hips and 137 knees that underwent irrigation and debridement (I&D) with partial component exchange were compared with 39 hips and 138 knees that underwent partial component exchange for aseptic indications. Line-item details of services billed during hospitalization were retrieved, and standardized direct medical costs were calculated in 2018 inflation-adjusted dollars. RESULTS: The mean direct medical cost of 2-stage revision THA performed for the treatment of PJI was significantly higher than that of aseptic revision THA ($58,369 compared with $22,846, p < 0.001). Similarly, the cost of 2-stage revision TKA performed for the treatment of PJI was significantly higher than that of aseptic revision TKA ($56,900 compared with $24,630, p < 0.001). Even when the total costs of aseptic revisions were doubled for a representative comparison with 2-stage procedures, the costs of PJI procedures were 15% to 28% higher than those of the doubled costs of aseptic revisions (p < 0.001). The mean direct medical cost of I&D procedures for PJI was about twofold higher than of partial component exchange for aseptic indications. CONCLUSIONS: The direct medical costs of operative treatment of PJI following THA and TKA are twofold higher than the costs of similar aseptic revisions. The high economic burden of PJI warrants efforts to reduce the incidence of PJI. Reimbursement schemes should account for the high costs of treating PJI in order to ensure sustainable patient care. LEVEL OF EVIDENCE: Economic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Manipulation Under Anesthesia After Total Knee: Who Still Requires a Revision Arthroplasty?

BACKGROUND: Stiffness after total knee arthroplasty (TKA) is a multifactorial complication involving patient, implant, surgical technique, and rehabilitation, occasionally necessitating manipulation under anesthesia (MUA) or revision. Few modern databases contain sufficient longitudinal information of all factors. We characterized MUA after primary TKA and identified independent risk factors for revision TKA after MUA from the American Joint Replacement Registry. METHODS: We retrospectively reviewed primary TKAs for American Joint Replacement Registry patients ≥65 years from January 1, 2012 to 31 March, 2019. We linked these to the Centers for Medicare and Medicaid Services database to identify MUA and revision TKA procedure codes. We compared groups with chi-squared testing, identifying independent risk factors for subsequent revision with binary logistic regression presented as odds ratios with 95% confidence intervals. RESULTS: Of 664,604 primary TKAs, 3918 (0.6%) underwent MUA after a median of 2.0 ± 1.0 months. Revision surgery occurred in 131 (3.4%) MUA patients after a median of 9.0 months. Timing of MUA was not different between revision and no revision patients (P = .09). Patients undergoing MUA compared to no MUA were older (age 71.5 vs 70.7, P < .01), predominantly female (63.9% vs 61.2%, P < .01), current/former tobacco users (24.2% vs 13.3%, P < .01), with osteoarthritis diagnoses (98.0% vs 84.3%, P < .01). Independent risk factors for revision after MUA were male gender (1.56, 1.09-2.22). CONCLUSION: The incidence of MUA after primary TKA is low (0.6%) in Medicare patients ≥65 years of age; 3.4% progress to revision after a median of 9 months. Being male was significantly associated with revision TKA after MUA.

Revision Total Hip Arthroplasty for the Treatment of Fracture: More Expensive, More Complications, Same Diagnosis-Related Groups: A Local and National Cohort Study.

BACKGROUND: Revision total hip arthroplasty (revision THA) occurs for a wide variety of indications and in the United States it is coded under Diagnosis-Related Groups (DRGs) 466, 467, and 468, which do not account for revision etiology, a potentially substantial driver of cost. This study investigates revision THA costs and 30-day complications by indication, both locally and nationally. METHODS: Hospitalization costs and complication rates for 1,422 aseptic revision THAs performed at a high-volume center between 2009 and 2014 were retrospectively reviewed. Additionally, charges for 28,133 revision THAs in the National Inpatient Sample (NIS) were converted to costs using the Healthcare Cost and Utilization Project cost-to-charge ratios, and 30-day complication rates for 3,224 revision THAs were obtained with use of the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP). Costs and complications were compared between revision THAs performed for fracture, wear/loosening, and dislocation/instability with use of simultaneous and pairwise comparisons and a multivariable model accounting for American Society of Anesthesiologists (ASA) score, age, and sex. RESULTS: Local hospitalization costs for fracture (median, $25,672) were significantly higher than those for wear/loosening ($20,228; p < 0.001) or dislocation/instability ($17,911; p < 0.001), with differences remaining significant even after adjusting for patient comorbidities (p < 0.001). NIS costs for fracture (median, $27,596) were higher than those for other aseptic indications (wear/loosening: $21,176, p < 0.001; dislocation/instability: $16,891, p< 0.001). Local 30-day orthopaedic complication rates for fracture (20.7%) were higher those than for dislocation/instability (9.0%; p = 0.007) and similar to those for wear/loosening (17.6%; p = 0.434). Nationally, combined medical and surgical complication rates for fracture (71.3% of patients with ≥1 complication) were significantly higher than those for wear/loosening (35.2%; p < 0.001) or dislocation/instability (35.1%; p < 0.001). CONCLUSIONS: Hospitalization costs for revision THA for fracture were 33% to 48% higher than for all other aseptic revision THAs, both locally and nationally. This increased cost persisted even after multivariable comorbidity adjustment, the current DRG basis for stratifying revision THA reimbursement. Additionally, 30-day complication rates suggest that increased resource utilization for fracture patients continues even after discharge. Indication-specific coding and reimbursement systems are necessary to maintain sustainable access to revision THA for all patients. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

What Are the Migration Patterns for U.S. Primary Total Joint Arthroplasty Patients?

BACKGROUND: Evaluation of total joint arthroplasty (TJA) patient-reported outcomes and survivorship requires that records of the index and potential revision arthroplasty procedure are reliably captured. Until the goal of the American Joint Replacement Registry (AJRR) of more-complete nationwide capture is reached, one must assume that patient migration from hospitals enrolled in the AJRR to nonAJRR hospitals occurs. Since such migration might result in loss to followup and erroneous conclusions on survivorship and other outcomes of interest, we sought to quantify the level of migration and identify factors that might be associated with migration in a specific AJRR population. QUESTIONS/PURPOSES: (1) What are the out-of-state and within-state migration patterns of U.S. Medicare TJA patients over time? (2) What patient demographic and institutional factors are associated with these patterns? METHODS: Hospital records of Medicare fee-for-service beneficiaries enrolled from January 1, 2004 to December 31, 2015, were queried to identify primary TJA procedures. Because of the nationwide nature of the Medicare program, low rates of loss to followup among Medicare beneficiaries, as well as long-established enrollment and claims processing procedures, this database is ideal for examining patient migration after TJA. We identified an initial cohort of 5.33 million TJA records from 2004 to 2016; after excluding patients younger than 65 years of age, those enrolled solely due to disability, those enrolled in a Medicare HMO, or residing outside the United States, the final analytical dataset consisted of 1.38 million THAs and 3.03 million TKAs. The rate of change in state or county of residence, based on Medicare annual enrollment data, was calculated as a function of patient demographic and institutional factors. A multivariate Cox model with competing risk adjustment was used to evaluate the association of patient demographic and institutional factors with risk of out-of-state or out-of-county (within-state) migration. RESULTS: One year after the primary arthroplasty, 0.61% (95% confidence interval [CI], 0.60-0.61; p < 0.001 for this and all comparisons in this Results section) of Medicare patients moved out of state and another 0.62% (95% CI, 0.60-0.63) moved to a different county within the same state. Five years after the primary arthroplasty, approximately 5.41% (95% CI, 5.39-5.44) of patients moved out of state and another 5.50% (95% CI, 5.46-5.54) Medicare patients moved to a different county within the same state. Among numerous factors of interest, women were more likely to migrate out of state compared with men (hazard ratios [HR], 1.06), whereas black patients were less likely (HR, 0.82). Patients in the Midwest were less likely to migrate compared with patients in the South (HR, 0.74). Patients aged 80 and older were more likely to migrate compared with 65- to 69-year-old patients (HR, 1.19). Patients with higher Charlson Comorbidity Index scores compared with 0 were more likely to migrate (index of 5+; HR, 1.19). CONCLUSIONS: Capturing detailed information on patients who migrate out of county or state, with associated changes in medical facility, requires a nationwide network of participating registry hospitals. At 5 years from primary arthroplasty, more than 10% of Medicare patients were found to migrate out of county or out of state, and the rate increases to 18% after 10 years. Since it must be assumed that younger patients might exhibit even higher migration levels, these findings may help inform public policy as a "best-case" estimate of loss to followup under the current AJRR capture area. Our study reinforces the need to continue aggressive hospital recruitment to the AJRR, while future research using an increasingly robust AJRR database may help establish the migration patterns of nonMedicare patients. LEVEL OF EVIDENCE: Level III, therapeutic study.

Creation and Validation of Linkage Between Orthopedic Registry and Administrative Data Using Indirect Identifiers.

BACKGROUND: Registries and administrative databases have unique and complementary strengths in device epidemiologic studies. We sought to develop, validate, and assess a sequential algorithm using indirect identifiers to link registry and administrative data. METHODS: Hip and knee arthroplasty procedures performed at 6 New York State hospitals enrolled in American Joint Replacement Registry in 2014 were included. After conducting a direct linkage using patient identifiers including name and social security numbers, we validated the methodology of indirect linkage using facility ID, patients' year and month of birth, sex, and zip code, and procedure date and site (hip/knee). We further evaluated the influence of absent indirect identifier(s) and compromised data quality on linkage success. RESULTS: Using our sequential algorithm, 3739 of the 4063 directly linked records (92.03%) were matched with indirect identifiers, with an accuracy of >99.9%. Main reasons for nonmatching included discrepancies in procedure codes and dates. When one of the indirect identifiers was not available, the linkage algorithm still achieved over 90% sensitivity and 99.8% accuracy. Analyses showed that the algorithm was robust when quality of data was moderately compromised. CONCLUSION: This study demonstrated high sensitivity and accuracy of an algorithm to create linkages between a registry and an administrative database using indirect identifiers. The methodology will enable long-term surveillance and outcome assessment of a wide variety of devices and procedures. Variations in the coding of procedures, availability of indirect identifiers, and their quality have limited impact on this algorithm.

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

BACKGROUND: Obesity prevalence continues to rise in the United States. We sought to examine the effect of obesity on length of hospital stay and direct medical costs in a large cohort of patients who underwent total knee arthroplasty. METHODS: The study included 8129 patients who had undergone 6475 primary total knee arthroplasties and 1654 revision total knee arthroplasties at a large U.S. medical center from January 1, 2000, to September 30, 2008. Patients with bilateral procedures within ninety days following the index admission were excluded. Data on clinical and surgical characteristics and complications were obtained from the original medical records and the institutional joint registry. Patients were classified into eight groups based on their body mass index at the time of surgery. Direct medical costs were calculated in 2010 U.S. dollars by using standardized, inflation-adjusted costs for services and procedures billed during hospitalization and the ninety-day window. Study end points were hospital length of stay and direct medical costs. End points were compared across the eight body mass index categories in both unadjusted and multivariable risk-adjusted analyses. Linear regression models were used to determine the cost impact associated with increasing body mass index and obesity accounting for comorbidities and complications. RESULTS: Body mass index data were available for 99.5% of patients and ranged from 15 to 73 kg/m2. Length of stay and the direct medical costs were lowest for patients with body mass index values in the normal to overweight range. Increasing body mass index was associated with significantly longer hospital stays and costs. Every 5-unit increase in body mass index beyond 30 kg/m2 was associated with approximately $250 to $300 higher hospitalization costs in primary total knee arthroplasty and $600 to $650 higher hospitalization costs in revision total knee arthroplasty. These estimates persisted after adjusting for comorbidities or complications. CONCLUSIONS: Obesity is associated with longer hospital stays and higher costs in total knee arthroplasty. The effect of obesity on costs appears to be independent of obesity-related comorbid conditions and complications.

Hospital costs of total hip arthroplasty for developmental dysplasia of the hip.

BACKGROUND: Developmental dysplasia of the hip (DDH) is a leading cause of total hip arthroplasty (THA) in younger patients. It is unknown how the hospital costs of THA in patients with DDH compare with patients with degenerative arthritis. QUESTIONS/PURPOSES: We undertook this study to determine (1) the hospital cost and length of stay associated with primary THA in patients with dysplasia compared with nondysplastic control subjects; (2) the hospital cost and length of stay of THA in severely dysplastic hips compared with mildly dysplastic hips; and (3) perioperative complications in patients with DDH compared with patients without dysplasia. METHODS: This matched-cohort study included 354 patients undergoing primary THA for DDH and 1029 age-, sex-, and calendar year-matched patients undergoing THA for primary osteoarthritis between 2000 and 2008. DDH severity was measured by the Crowe classification. An institutional database was used to calculate the cost of care. Using line item details (date, type, frequency, and billed charge) for every procedure or service billed at our institution for each patient, bottom-up microcosting valuation techniques were used to generate standardized inflation-adjusted estimates of the cost of each service or procedure in constant dollars. Generalized linear random effects models were used to compare length of stay and costs during hospitalization and the 90-day period after surgery. Query of a longitudinal institutional database was used to identify documented complications. RESULTS: Patients with DDH undergoing primary THA incurred higher hospital costs than patients with primary osteoarthritis (USD 16,949 versus USD 16,485, p = 0.012). Operating room costs (USD 3471 versus USD 3417, p = 0.0085) and implant costs (USD 3896 versus USD 3493, p < 0.001) were higher in the DDH group compared with the osteoarthritis group. Length of stay was not different between the two groups (4 versus 4 days, p = 0.46). Crowe 4 hips had higher hospital costs than Crowe 1 hips (USD 21,246 versus USD 16,345, p < 0.001) with an associated longer length of stay (5 days versus 4 days, p = 0.0011) and higher implant costs (USD 4380 versus USD 3788, p = 0.0012). There was no detectible difference in 90-day complications in the case group compared with patients undergoing THA for osteoarthritis. CONCLUSIONS: Hospital cost of primary THA is approximately USD 450 higher in patients with DDH compared with osteoarthritis. Increased severity of dysplasia (Crowe classification) was associated with higher costs. LEVEL OF EVIDENCE: Level IV, economic and decision analyses. See Guidelines for Authors for a complete description of levels of evidence.

Obesity increases length of stay and direct medical costs in total hip arthroplasty.

BACKGROUND: The number of obese patients undergoing THA is increasing. Previous studies have shown that obesity is associated with an increased likelihood of complications after THA, but there is little information regarding the impact of obesity on medical resource use and direct medical costs in THA. QUESTIONS/PURPOSES: We sought to examine the relationship between obesity, length of stay, and direct medical costs in a large cohort of patients undergoing THAs. METHODS: The study included 8973 patients who had undergone 6410 primary and 2563 revision THAs at a large US medical center between January 1, 2000, and September 31, 2008. Patients with bilateral procedures within 90 days after index admission and patients with acute trauma were excluded. Data regarding clinical, surgical characteristics, and complications were obtained from the original medical records and the institutional joint registry. Patients were classified into eight groups based on their BMI at the time of surgery. Direct medical costs were calculated by using standardized, inflation-adjusted costs for services and procedures billed during hospitalization and the 90-day window. Study end points were hospital length of stay, direct medical costs during hospitalization, and the 90-day window. End points were compared across the eight BMI categories in multivariable risk-adjusted linear regression models. RESULTS: Mean length of stay and the direct medical costs were lowest for patients with a BMI of 25 to 35 kg/m(2). Increasing BMI was associated with longer hospital stays and costs. Every five-unit increase in BMI beyond 30 kg/m(2) was associated with approximately USD $500 higher hospital costs and USD $900 higher 90-day costs in primary THA (p = 0.0001), which corresponded to 5% higher costs. The cost increase associated with BMI was greater in the revision THA cohort where every five-unit increase in BMI beyond 30 kg/m(2) was associated with approximately USD $800 higher hospital costs and USD $1500 higher 90-day costs. These estimates remained unchanged after adjusting for comorbidities or complications. CONCLUSIONS: Obesity is associated with longer hospital stays and higher costs in THA. The significant effect of obesity on costs persists even among patients without comorbidities but the increased costs associated with obesity may be balanced by the potential benefits of THA in the obese. Increasing prevalence of obesity likely contributes to the increasing financial burden of THA worldwide. LEVEL OF EVIDENCE: Level IV, economic and decision analyses. See the Instructions for Authors for a complete description of levels of evidence.

Income and patient-reported outcomes (PROs) after primary total knee arthroplasty.

BACKGROUND: To assess whether income is associated with patient-reported outcomes (PROs) after primary total knee arthroplasty (TKA). METHODS: We used prospectively collected data from the Mayo Clinic Total Joint Registry to assess the association of income with index knee functional improvement, moderate to severe pain and moderate to severe activity limitation at 2-year and 5-year follow-up after primary TKA using multivariable-adjusted logistic regression analyses. RESULTS: There were 7, 139 primary TKAs at 2 years and 4, 234 at 5 years. In multivariable-adjusted analyses, at 2-year follow-up, compared to income > US$45, 000, lower incomes of ≤ US$35, 000 and > US$35, 000 to 45, 000 were associated (1) significantly with moderate to severe pain with an odds ratio (OR) 0.61 (95% CI 0.40 to 0.94) (P = 0.02) and 0.68 (95% CI 0.49 to 0.94) (P = 0.02); and (2) trended towards significance for moderate to severe activity limitation with OR 0.78 (95% CI 0.60 to 1.02) (P = 0.07) and no significant association with OR 0.96 (95% CI 0.78 to 1.20) (P = 0.75), respectively. At 5 years, odds were not statistically significantly different by income, although numerically they favored lower income. In multivariable-adjusted analyses, overall improvement in knee function was rated as 'better' slightly more often at 2 years by patients with income in the ≤ US$35, 000 range compared to patients with income > US$45, 000, with an OR 1.9 (95% CI 1.0 to 3.6) (P = 0.06). CONCLUSIONS: We found that patients with lower income had better pain outcomes compared to patients with higher income. There was more improvement in knee function, and a trend towards less overall activity limitation after primary TKA in lower income patients compared to those with higher incomes. Insights into mediators of these relationships need to be investigated to understand how income influences outcomes after TKA.

Determinants of direct medical costs in primary and revision total knee arthroplasty.

BACKGROUND: TKA procedures are increasing rapidly, with substantial cost implications. Determining cost drivers in TKA is essential for care improvement and informing future payment models. QUESTIONS/PURPOSES: We determined the components of hospitalization and 90-day costs in primary and revision TKA and the role of demographics, operative indications, comorbidities, and complications as potential determinants of costs. METHODS: We studied 6475 primary and 1654 revision TKA procedures performed between January 1, 2000, and September 31, 2008, at a single center. Direct medical costs were measured by using standardized, inflation-adjusted costs for services and procedures billed during the 90-day period. We used linear regression models to determine the cost impact associated with individual patient characteristics. RESULTS: The largest proportion of costs in both primary and revision TKA, respectively, were for room and board (28% and 23%), operating room (22% and 17%), and prostheses (13% and 24%). Prosthesis costs were almost threefold higher in revision TKA than in primary TKA. Revision TKA procedures for infections and bone and/or prosthesis fractures were approximately 25% more costly than revisions for instability and loosening. Several common comorbidities were associated with higher costs. Patients with vascular and infectious complications had longer hospital stays and at least 80% higher 90-day costs as compared to patients without complications. CONCLUSIONS: High prosthesis costs in revision TKA represent a factor potentially amenable to cost containment efforts. Increased costs associated with demographic factors and comorbidities may put providers at financial risk and may jeopardize healthcare access for those patients in greatest need.

A collaborative of leading health systems finds wide variations in total knee replacement delivery and takes steps to improve value.

Members of a consortium of leading US health care systems, known as the High Value Healthcare Collaborative, used administrative data to examine differences in their delivery of primary total knee replacement. The goal was to identify opportunities to improve health care value by increasing the quality and reducing the cost of that procedure. The study showed substantial variations across the participating health care organizations in surgery times, hospital lengths-of-stay, discharge dispositions, and in-hospital complication rates. The study also revealed that higher surgeon caseloads were associated with shorter lengths-of-stay and operating time, as well as fewer in-hospital complications. These findings led the consortium to test more coordinated management for medically complex patients, more use of dedicated teams, and a process to improve the management of patients' expectations. These innovations are now being tried by the consortium's members to evaluate whether they increase health care value.