Orthopedics

Feature Article Supplemental Data

Preoperative Bariatric Surgery and the Risk of Readmission Following Total Joint Replacement

James X. Liu, MD; Albit R. Paoli, BS; Siddharth A. Mahure, MD, MBA; Joseph Bosco III, MD; Kirk A. Campbell, MD

Abstract

The purpose of this study was to compare nonelective and all-cause readmission rates and to identify risk factors for readmission of total joint arthroplasty (TJA) patients who had preoperative bariatric surgery (BS) compared with TJA patients without preoperative BS. The New York Statewide Planning and Research Cooperative System database was queried to identify 343,710 TJA patients between 2005 and 2014. Three patient groups were evaluated: group 1 (patients with preoperative BS within 2 years of TJA [N=1478]); group 2 (obese patients without preoperative BS [N=60,259]); and group 3 (nonobese patients without preoperative BS [N=281,973]). Nonelective and all-cause readmission rates (30 days, 90 days, and 1 year) were compared, and multivariate analyses of readmission risk factors were performed. Group 1 had no significant difference in nonelective readmission rates compared with groups 2 and 3. However, when elective TJA readmissions were included, group 1 had significantly higher all-cause readmission rates at 30 days, 90 days, and 1 year compared with groups 2 and 3. Bariatric surgery was not a risk factor for nonelective readmissions at any time point. When elective TJA admissions were included, BS was an independent risk factor for all-cause readmission at all time points. Patients who have BS prior to TJA do not have higher nonelective readmission rates than obese TJA patients without BS. Bariatric surgery is not a risk factor for nonelective readmissions. However, BS is a significant predictor of elective TJA admissions up to 1 year following the index TJA. [Orthopedics. 2018; 41(2):107–114.]

Abstract

The purpose of this study was to compare nonelective and all-cause readmission rates and to identify risk factors for readmission of total joint arthroplasty (TJA) patients who had preoperative bariatric surgery (BS) compared with TJA patients without preoperative BS. The New York Statewide Planning and Research Cooperative System database was queried to identify 343,710 TJA patients between 2005 and 2014. Three patient groups were evaluated: group 1 (patients with preoperative BS within 2 years of TJA [N=1478]); group 2 (obese patients without preoperative BS [N=60,259]); and group 3 (nonobese patients without preoperative BS [N=281,973]). Nonelective and all-cause readmission rates (30 days, 90 days, and 1 year) were compared, and multivariate analyses of readmission risk factors were performed. Group 1 had no significant difference in nonelective readmission rates compared with groups 2 and 3. However, when elective TJA readmissions were included, group 1 had significantly higher all-cause readmission rates at 30 days, 90 days, and 1 year compared with groups 2 and 3. Bariatric surgery was not a risk factor for nonelective readmissions at any time point. When elective TJA admissions were included, BS was an independent risk factor for all-cause readmission at all time points. Patients who have BS prior to TJA do not have higher nonelective readmission rates than obese TJA patients without BS. Bariatric surgery is not a risk factor for nonelective readmissions. However, BS is a significant predictor of elective TJA admissions up to 1 year following the index TJA. [Orthopedics. 2018; 41(2):107–114.]

The obesity epidemic is well established in the United States, affecting an estimated 35% of the adult population.1 Obesity rates are higher among patients undergoing total joint arthroplasty (TJA), estimated at greater than 50% and approximately 40% in the total knee arthroplasty and total hip arthroplasty patient populations, respectively.2,3 Obesity is a risk factor for poor patient outcomes following TJA and is associated with increased postoperative complications.4 There has been recent interest in studying the effects of bariatric surgery (BS) prior to total knee or total hip replacement surgery.5–7 However, there is conflicting evidence regarding the effect of preoperative BS prior to TJA, with several studies reporting favorable results6,8–10 and others reporting mixed or worse results.3,5,7,11,12

All-cause hospital readmission rates are used by payers, including the government, as a surrogate for quality and cost of care.13 The few studies that have evaluated readmission rates in the preoperative BS population have reported conflicting results.3,9 Previous studies have had fewer than 200 patients who underwent preoperative BS. No large studies have evaluated the independent risk factors for readmission in the preoperative BS population.

The purpose of this study was to compare nonelective and all-cause readmission rates and to identify independent risk factors and the top causes for readmission of patients who had BS within 2 years prior to TJA compared with patients who had not undergone BS prior to TJA.

Materials and Methods

Study Design

The authors used the New York Statewide Planning and Research Cooperative System database to conduct a retrospective cohort analysis. They queried the New York Statewide Planning and Research Cooperative System database for International Classification of Diseases, Ninth Revision (ICD-9) codes 81.51 (total hip arthroplasty) and 81.54 (total knee arthroplasty) to identify all patients who underwent TJA between 2005 and 2014. During this period, a total of 417,197 TJA procedures were reported, for which there were 343,710 unique patients. Patients who underwent TJA were tracked retrospectively to determine if they had a diagnosis code for obesity and whether they underwent a BS within 2 years prior to the TJA procedure. The ICD-9 codes for obesity (278.0, 278.00, 278.01, 278.02, V85.35, V85.37, V85.38, V85.39, V85.4, V77.8) and BS (44.31, 44.38, 44.39, 44.68, 44.95, 44.96, 44.97, 44.98, 44.5, 44.99, 44.69, 43.89, 45.50, 45.51, 45.90, 45.91, 43.7, 43.5, 43.6, 44.93, 44.99, V45.86) were used for patient group selections.3 Patients who had an ICD-9 diagnostic code for cancer or who were younger than 18 years were excluded from the analysis.14,15 Patients were categorized into 3 distinct cohorts: group 1 (obese patients who underwent BS within 2 years prior to TJA [N=1478]); group 2 (patients diagnosed with obesity who did not undergo BS within 2 years prior to TJA [N=60,259]); and group 3 (patients who were not obese and did not undergo BS [N=281,973]).

Patient cohorts were then followed prospectively for a period of 1 year after undergoing the index TJA to determine the readmission rates at 30 days, 90 days, and 1 year. Patient demographics, comorbidities, and surgeon volume were recorded for each patient. Hospital metrics (number of beds, teaching status, location, and cost-to-charge ratios) were obtained using facility-specific data from the Healthcare Cost Report Information System for the Centers for Medicare & Medicaid Services.16 Total hospital costs were estimated by adjusting total hospital charges for inflation to year 2014 and applying facility-specific cost-to-charge ratios. Preoperative comorbidity diagnoses for each of the patients were defined using the Elixhauser comorbidity method.17–19 Elixhauser comorbidity method scores were calculated by weighting each comorbidity equally and grading overall score as the sum of the total number of comorbidities. Principal study outcomes were nonelective and all-cause readmission rates and costs at 30 days, 90 days, and 1 year; the top causes (diagnoses and interventions) for readmission; and the independent risk factors for readmission.

Data Analysis and Statistics

All analyses were conducted with R Core Team 2016 statistical software (R Foundation for Statistical Computing, Vienna, Austria). Categorical variables were compared with Pearson's chi-square test (Fisher's exact test was applied if there were fewer than 5 observations per cell). P values for numeric variables were calculated using analysis of variance. Post hoc testing was conducted for numeric variables using Tukey's test for pairwise comparisons between means.

A binary logistic regression model was built by selecting those patients in groups 1 and 2 only and assigning readmission status at 30 days, 90 days, and 1 year as the dependent variable. The model was controlled by patient demographics and comorbidities, surgeon volume, hospital teaching status, hospital location, and hospital size using the results from bivariate analyses.20,21 Thirty-day, 90-day, and 1-year analyses were conducted evaluating (1) nonelective readmissions, which consisted of patients who underwent an unscheduled readmission following the initial TJA; and (2) all-cause readmissions, which consisted of all inpatient hospital readmissions within the selected time periods, including subsequent planned, elective TJA admissions. P<.05 was considered statistically significant.

Results

Readmitted Patient Population Characteristics

Demographics for nonelective readmissions showed that, compared with group 2, group 1 patients were more likely to be female (10.10% vs 8.18%, P=.019), between the ages of 45 and 64 years (9.20% vs 5.19%, P<.001), and covered by private insurance (6.90% vs 4.22%, P<.001). Patient and hospital characteristics are presented in Table 1.

Characteristics of 343,710 Patients Undergoing TJA With and Without Prior Bariatric SurgeryCharacteristics of 343,710 Patients Undergoing TJA With and Without Prior Bariatric Surgery

Table 1:

Characteristics of 343,710 Patients Undergoing TJA With and Without Prior Bariatric Surgery

Readmission Rates, Costs, and Readmitted Patient Characteristics

When comparing nonelective readmission rates, there was no significant difference between groups 1 and 2 at 30 days (5.62% vs 4.56%, P=.094), 90 days (7.04% vs 6.41%, P=.542), and 1 year (13.90% vs 12.40%, P=.153) (Table 1). When comparing all-cause readmission rates, including patients who were readmitted for elective TJA, patients in group 1 were more likely to be readmitted than patients in group 2 and group 3 at 30 days, 90 days, and 1 year (Table 1). All-cause readmission rates for group 1 vs group 2 were 6.50% vs 4.84% (P=.006) at 30 days, 9.61% vs 7.26% (P=.001) at 90 days, and 22.60% vs 15.90% (P<.001) at 1 year. No difference in all-cause readmission total charges or costs was observed between group 1 and group 2 at 30 days.

Most Common Causes of All-Cause Readmission at 30 Days, 90 Days, and 1 Year

Total knee replacement was the most common cause of overall readmission for group 1 at 30 days (0.95%), 90 days (2.23%), and 1 year (7.71%), with significantly increased rates for group 1 when compared with groups 2 and 3 (P<.001). The top 3 interventions for all-cause readmission at the 1-year period for group 1 vs group 2 were elective total knee replacement (7.71% vs 2.94%, P<.001), elective total hip replacement (1.56% vs 0.84%, P=.007), and revision TJA (0.95% vs 1.05%, P=.807). Debridement of wound infection was significantly higher in group 1 compared with group 2 at the 90-day readmission period (0.54% vs 0.24%, P=.030) (Table 2).

Top Causes of Hospital Readmission for 343,710 Patients Undergoing TJA With and Without Prior Bariatric SurgeryTop Causes of Hospital Readmission for 343,710 Patients Undergoing TJA With and Without Prior Bariatric Surgery

Table 2:

Top Causes of Hospital Readmission for 343,710 Patients Undergoing TJA With and Without Prior Bariatric Surgery

Patient Characteristics That Were Readmission Risk Factors

Binary logistic regression analysis showed that BS, although elevating risk of readmission, was not a statistically significant independent risk factor for nonelective readmission at 30 days (odds ratio [OR], 1.25 [95% confidence interval (CI), 0.99–1.55]), 90 days (OR, 1.11 [95% CI, 0.90–1.35]), or 1 year (OR, 1.14 [95% CI, 0.98–1.32]) (Tables AC, available in the online version of the article). Age 65 years and older, African American ethnicity, and Medicare or Medicaid coverage were risk factors for readmission at all time points. Workers' compensation was an independent risk factor for 1-year readmission.

Risk-Adjusted Odds Ratio of 30 Day Non-elective Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without prior bariatric surgery (BS)

Table A:

Risk-Adjusted Odds Ratio of 30 Day Non-elective Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without prior bariatric surgery (BS)

Risk-Adjusted Odds Ratio of 90 Day Non-elective Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without prior bariatric surgery (BS)

Table B:

Risk-Adjusted Odds Ratio of 90 Day Non-elective Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without prior bariatric surgery (BS)

Risk-Adjusted Odds Ratio of 1 Year Non-elective Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without Prior Bariatric Surgery (BS)

Table C:

Risk-Adjusted Odds Ratio of 1 Year Non-elective Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without Prior Bariatric Surgery (BS)

When patients who were admitted for elective TJA were included, preoperative BS was an independent risk factor for all-cause readmission at 30 days (OR, 1.37 [95% CI, 1.10–1.68]), 90 days (OR, 1.36 [95% CI, 1.13–1.61]), and 1 year (OR, 1.54 [95% CI, 1.36–1.75]) (Tables DF, available in the online version of the article). Age 65 years and older, African American ethnicity, and Medicare or Medicaid coverage were risks factors for readmission at all time points. Female sex was a risk factor for 1-year readmission. Preexisting comorbidities are listed in Tables AF.

Risk-Adjusted Odds Ratio of 30 Day All-cause Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without prior bariatric surgery (BS), including elective TJA readmissions

Table D:

Risk-Adjusted Odds Ratio of 30 Day All-cause Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without prior bariatric surgery (BS), including elective TJA readmissions

Risk-Adjusted Odds Ratio of 90 Day All-cause Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without prior bariatric surgery (BS), including elective TJA readmissions

Table E:

Risk-Adjusted Odds Ratio of 90 Day All-cause Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without prior bariatric surgery (BS), including elective TJA readmissions

Risk-Adjusted Odds Ratio of 1 Year All-cause Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without prior bariatric surgery (BS), including elective TJA readmissions

Table F:

Risk-Adjusted Odds Ratio of 1 Year All-cause Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without prior bariatric surgery (BS), including elective TJA readmissions

Surgeon Volume as a Readmission Risk Factor

On evaluation of surgeon volume as a risk factor in nonelective readmissions, primary TJA performed by high-volume or very high-volume surgeons was associated with lower odds of 30-day, 90-day, and 1-year nonelective readmissions compared with primary TJA performed by medium- and low-volume surgeons. All-cause readmissions showed similar results, with very high-volume and high-volume surgeons being associated with lower readmission risk (Tables DF).

Hospital Characteristics That Were Readmission Risk Factors

Patients who underwent TJA at non-teaching hospitals had greater odds of nonelective readmission at 30 days (OR, 1.31 [95% CI, 1.20–1.42]), 90 days (OR, 1.34 [95% CI, 1.24–1.44]), and 1 year (OR, 1.31 [95% CI, 1.24–1.39]) than patients who underwent TJA at teaching hospitals. Hospital location showed significance at all readmission periods, with patients undergoing TJA in rural hospitals having greater odds of nonelective readmission than patients undergoing TJA in urban hospitals (Tables AC). Similar to nonelective readmissions, nonteaching and rural hospitals were associated with increased risks of all-cause readmissions (Tables DF).

Discussion

The current study had several limitations. Like other observational studies involving the use of large health care registries, this study was subject to miscoding and noncoding errors.22 The authors believe that the proven validity of the New York Statewide Planning and Research Cooperative System database and the robustness of their methods for extracting and analyzing the data helped mitigate these potential systematic errors. Because the New York Statewide Planning and Research Cooperative System database does not contain patients' body mass index information, the authors relied on previously published ICD-9 diagnosis codes for identifying obese patients. Although the authors used diagnosis codes from similar previously published studies, such as the codes used by Inacio et al,3 the identification of these patients may have been affected by a selection bias type of error. The effect of using ICD-9 codes instead of patients' body mass index for identifying obese patients in the TJA population has been previously studied. George et al23 evaluated the difference in patient characteristics and hospital outcomes between ICD-9–diagnosed obesity vs body mass index–diagnosed obesity, finding that the prevalence of ICD-9–diagnosed obesity in a large database registry can under-represent the actual prevalence of obesity. In their study, ICD-9–diagnosed patients were more likely to have a higher grade of obesity than body mass index–diagnosed patients.23 In the current study, the findings could translate to obese patients missing ICD-9 diagnoses and being erroneously assigned to the nonobese control group (group 3). Despite these limitations, the authors believe that a true comparison was performed to evaluate the impact of BS prior to TJA in ICD-9 obese patients. The comparison groups of interest (group 1 and group 2) were selected from the same cohort (ICD-9–diagnosed obesity) and had body mass index representative of the obese population. Also, the current study considered obesity as a single category and did not evaluate the effects of varying severity of obesity or individual ICD-9 codes for obesity. Furthermore, although this study attempted to sample a representative TJA population in the United States, only data from New York state were included; caution should be exercised when extrapolating these data to other areas.

There has been a recent focus on the development and implementation of new payment and service delivery models, such as the Centers for Medicare & Medicaid Services' Comprehensive Care for Joint Replacement model, which aims to improve the quality of care for patients undergoing lower extremity joint replacements.24 All-cause readmission rates following TJA are an important measurement of quality per the Comprehensive Care for Joint Replacement guidelines, although few studies have specifically addressed readmission rates.3,9

In a study that investigated the postoperative complications of English National Health Service patients who underwent TJA, postoperative outcomes were measured in 143 patients who had BS either before or after TJA. Bariatric surgery was performed first in 53 patients followed by arthroplasty, and arthroplasty was performed first in 90 patients followed by BS. There was a mean 1.1% (range. 0.1%–6.6%) 30-day readmission rate for patients who had BS prior to TJA, which was roughly 7 times less than the readmission rate for patients who had TJA prior to BS (mean, 7.5%; range, 2.5%–18.4%) (P=.06).9 Although the study evaluated patients who had BS prior to TJA, there was no comparison with patients who had TJA but not BS. Thus, there was no true comparison group.

A recent study evaluated postoperative outcomes and readmission rates in a patient cohort stratified into 3 groups: patients with BS more than 2 years prior to TJA (n=69), patients who had BS within 2 years of TJA (n=102), and patients who did not undergo BS but were candidates for the procedure (n=11,032). The 30-day readmission rate was highest in the nonbariatric group (3.8%), followed by patients who had BS more than 2 years prior to TJA (2.9%). The readmission rate was 0% for patients who had BS within 2 years of TJA. The 90-day readmission rate was highest in patients who had BS more than 2 years prior to TJA (7.2%), followed by the non-BS group (5.9%) and the group who had BS within 2 years of TJA (2.5%). At each time period, patients who had BS within 2 years of TJA had the lowest readmission rates. The authors also reported a revision density of 3.4 per 100 years of observation, which was highest in patients who had BS more than 2 years prior to TJA, concluding that BS prior to TJA may not yield dramatic improvements in postoperative outcomes.3

To the current authors' knowledge, there has not been a multivariate analysis of risk factors for readmission specifically in the preoperative BS population prior to TJA. Examining only the readmission rates of patients with and without BS does not control for confounding factors that will affect readmission, such as patient age, demographics, and race, hospital characteristics, and preoperative patient comorbidities. If patient comorbidities are not controlled for, it cannot be concluded that BS increases the risk for readmission if BS patients had higher rates of preoperative comorbidities that predispose them to hospital readmission. Thus, a logistic regression analysis was used to control for patient comorbidities and other possible confounding variables. The data indicate that preoperative BS patients are more likely to undergo an elective TJA compared with the other groups. However, unplanned surgeries also have a major influence on readmission rates, especially within the 30- and 90-day period, when wound infection debridement and revision TJA represent the second and third most common reasons for readmission.

Conclusion

Patients who had BS within 2 years prior to TJA did not have significantly higher nonelective readmission rates at 30 days, 90 days, and 1 year than obese and nonobese patients without preoperative BS. However, when elective TJA was included as an admission, patients with preoperative BS had significantly higher readmission rates at all time points. Preoperative BS is not an independent risk factor for nonelective readmissions. However, it is a significant predictor of elective TJA admissions and thus an independent risk factor for all-cause readmissions following TJA. Future studies are required not only to verify this trend nationwide but also to determine the long-term effects of preoperative BS prior to TJA.

References

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Characteristics of 343,710 Patients Undergoing TJA With and Without Prior Bariatric Surgery

CharacteristicGroup 1 Obesity and BS Prior to TJA (N=1478)Group 2 Obesity Without BS Prior to TJA (N=60,259)Group 3 No Obesity and No BS Prior to TJA (N=281,973)Pa

Group 1 vs Group 2Group 1 vs Group 3Group 2 vs Group 3
Nonelective readmission rates
  30-day readmission5.62%4.56%5.17%.094.474<.001
    Total charges ($)39,373 (±31,945)36,629 (±30,847)35,863 (±32,815).405.222.106
    Total costs ($)13,487 (±9666)13,393 (±10,928)13,095 (±11,217).991.852.056
  90-day readmission7.04%6.41%7.29%.542.751<.001
    Total charges ($)39,214 (±32,945)36,161 (±33,476)35,686 (±34,910).349.238.429
    Total costs ($)13,402 (±10,026)13,195 (±11,258)13,024 (±11,898).959.867.389
  1-year readmission13.90%12.40%14.40%.153.609<.001
    Total charges ($)37,596 (±34,858)35,926 (±39,140)36,082 (±42,743).754.789.922
    Total costs ($)12,712 (±10,176)13,080 (±12,576)13,133 (±13,952).879.841.913
All-cause readmission rates, including elective TJA readmissions
  30-day readmission6.50%4.84%5.43%.006.082<.001
    Total charges ($)39,977 (±32,266)36,792 (±30,710)36,049 (±32,698).284.142.115
    Total costs ($)13,596 (±9567)13,450 (±10,879)13,154 (±11,204).978.811.056
  90-day readmission9.61%7.26%8.03%.001.030<.001
    Total charges ($)40,134 (±32,554)36,493 (±33,048)35,992 (±34,568).183.106.367
    Total costs ($)13,711 (±9685)13,337 (±11,110)13,147 (±11,797).856.697.289
  1-year readmission22.60%15.90%17.30%<.001<.001<.001
    Total charges ($)39,529 (±32,821)36,923 (±37,374)36,798 (±41,186).381.338.937
    Total costs ($)13,779 (±9491)13,524 (±12,002)13,445 (±13,449).916.857.783
Readmission demographics
  Age group
    20–44 y0.74%0.26%0.34%.005.015.005
    45–64 y9.20%5.19%3.75%<.001<.001<.001
    65+ y2.98%6.45%9.89%<.001<.001<.001
Sex
  Male3.79%4.23%5.88%.439.001<.001
  Female10.10%8.18%8.49%.019.033.019
Ethnicity
  White10.40%9.38%11.20%.287.377<.001
  African American2.03%1.56%1.37%.184.057.001
  Hispanic0.74%0.73%0.92%1.000.835<.001
  Other0.61%0.69%0.83%.824.646.002
Insurance
  Medicare5.35%6.82%9.70%.030<.001<.001
  Medicaid1.15%0.94%0.83%.489.352.035
  Private6.90%4.22%3.48%<.001<.001<.001
  Workers' compensation0.34%0.23%0.20%.403.345.345
  Other insurance0.14%0.19%0.15%1.0001.000.041
Surgeon volumeb
  Very high27.80%31.80%30.30%.378.486.025
  High39.00%34.80%32.20%.234.065<.001
  Medium27.80%28.00%30.10%1.000.799.001
  Low3.90%3.61%5.60%.974.548<.001
Hospital characteristics
  Teaching status
    Teaching73.20%74.20%74.00%.845.845.845
    Nonteaching26.80%25.80%26.00%.845.845.845
  Hospital location
    Urban94.60%91.10%93.20%.150.495<.001
    Rural5.37%8.92%6.82%.150.495<.001
  Hospital sizec
    Small39.50%39.40%37.60%1.000.937.008
    Medium29.30%28.20%31.70%.789.742<.001
    Large31.20%32.40%30.70%.921.921.009

Top Causes of Hospital Readmission for 343,710 Patients Undergoing TJA With and Without Prior Bariatric Surgery

Cause of ReadmissionGroup 1 Obesity and BS Prior to TJA (N=1478)Group 2 Obesity Without BS Prior to TJA (N=60,259)Group 3 No Obesity and No BS Prior to TJA (N=281,973)Pa

Group 1 vs Group 2Group 1 vs Group 3Group 2 vs Group 3
30-day readmission
  Top diagnoses
    Other postoperative infection0.68%0.49%0.33%.397.051<.001
    Infection and inflammatory reaction due to internal joint prosthesis0.47%0.37%0.26%.643.169<.001
    Dislocation of prosthetic joint0.07%0.10%0.17%1.000.793<.001
    Osteoarthrosis lower leg1.29%0.38%0.31%<.001<.001.006
    Atrial fibrillation0.07%0.11%0.13%1.0001.000.523
    Cellulitis and abscess of leg except foot0.14%0.15%0.10%1.000.987.003
    Hematoma complicating a procedure0.14%0.10%0.10%.822.822.822
    Other complications due to internal joint prosthesis0.14%0.10%0.10%.707.707.707
    Unspecified septicemia0.14%0.06%0.10%.359.658.030
    Periprosthetic fracture around prosthetic joint0.00%0.08%0.09%.651.651.651
  Top interventions
    Transfusion of packed cells0.07%0.19%0.30%.536.216<.001
    Total knee replacement0.95%0.25%0.18%<.001<.001.001
    Injection of antibiotic0.14%0.19%0.18%1.0001.0001.000
    Diagnostic ultrasound of peripheral vascular system0.20%0.10%0.11%.366.366.465
    Debridement of wound infection0.41%0.18%0.12%.057.014.001
    Closed reduction of dislocation of hip0.07%0.04%0.11%.7391.000<.001
    Arthrocentesis0.20%0.09%0.09%.252.252.933
    Injection or infusion of other therapeutic or prophylactic substance0.07%0.08%0.09%1.0001.0001.000
    Venous catheterization not elsewhere classified0.14%0.10%0.08%.667.514.385
    Revision TJA0.34%0.35%0.37%1.0001.0001.000
90-day readmission
  Top diagnoses
    Other postoperative infection0.81%0.57%0.36%.305.013<.001
    Infection and inflammatory reaction due to internal joint prosthesis0.47%0.47%0.33%1.000.533<.001
    Osteoarthrosis lower leg2.84%0.91%0.74%<.001<.001<.001
    Dislocation of prosthetic joint0.07%0.15%0.23%.730.412.001
    Atrial fibrillation0.07%0.14%0.17%.727.727.727
    Cellulitis and abscess of leg except foot0.14%0.21%0.13%.774.774<.001
    Other complications due to internal joint prosthesis0.14%0.13%0.13%.765.765.765
    Unspecified septicemia0.14%0.08%0.13%.479.718.002
    Intestinal infection due to Clostridium difficile0.00%0.07%0.13%.628.410.001
    Pneumonia organism unspecified0.00%0.07%0.12%.628.409.003
  Top interventions
    Total knee replacement2.23%0.65%0.48%<.001<.001<.001
    Transfusion of packed cells0.07%0.21%0.34%.379.170<.001
    Total hip replacement0.41%0.23%0.30%.256.467.018
    Injection of antibiotic0.14%0.23%0.23%.903.903.903
    Diagnostic ultrasound of peripheral vascular system0.20%0.12%0.13%.659.659.659
    Debridement of wound infection0.54%0.24%0.15%.030.003<.001
    Closed reduction of dislocation of hip0.07%0.06%0.14%.728.728<.001
    Esophagogastroduodenoscopy with closed biopsy0.14%0.08%0.13%.532.711.020
    Injection or infusion of other therapeutic or prophylactic substance0.07%0.10%0.12%1.0001.000.924
    Revision TJA0.41%0.51%0.54%.719.719.719
1-year readmission
  Top diagnoses
    Osteoarthrosis lower extremity9.27%3.93%3.27%<.001<.001<.001
    Infection and inflammatory reaction due to internal joint prosthesis0.74%0.61%0.47%.637.258<.001
    Other postoperative infection0.81%0.60%0.39%.383.025<.001
    Dislocation of prosthetic joint0.41%0.25%0.35%.428.902<.001
    Atrial fibrillation0.20%0.28%0.31%.802.802.684
    Coronary atherosclerosis of native coronary artery0.14%0.25%0.32%.591.516.016
    Other complications due to internal joint prosthesis0.20%0.26%0.26%1.0001.0001.000
    Pneumonia organism unspecified0.14%0.21%0.27%.773.676.028
    Other chest pain0.27%0.29%0.25%1.0001.000.213
    Cellulitis and abscess of leg except foot0.20%0.36%0.22%.6531.000<.001
  Top interventions
    Total knee replacement7.71%2.94%2.04%<.001<.001<.001
    Total hip replacement1.56%0.84%1.15%.007.183<.001
    Transfusion of packed cells0.14%0.25%0.44%.594.178<.001
    Injection of antibiotic0.14%0.37%0.37%.307.3071.000
    Percutaneous transluminal coronary angioplasty0.14%0.21%0.27%.774.676.058
    Diagnostic ultrasound of heart0.20%0.21%0.23%1.0001.0001.000
    Esophagogastroduodenoscopy with closed biopsy0.27%0.16%0.21%.465.560.049
    Injection or infusion of other therapeutic or prophylactic substance0.07%0.17%0.20%.524.524.398
    Left heart cardiac catheterization0.20%0.21%0.19%1.0001.000.940
    Revision TJA0.95%1.05%1.14%.807.807.163

Risk-Adjusted Odds Ratio of 30 Day Non-elective Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without prior bariatric surgery (BS)

30 Day Readmission30 Day ReadmissionOR (95% CI)P-value*

NoYes
N=58908N=2829
Group:
  2 (+) Obesity (−) BS Prior to TJA97.60%97.10%Ref.Ref.
  1 (+) Obesity (+) BS Prior to TJA2.37%2.93%1.25 [0.99;1.55]0.061
Age group:
  Between 45 and 6449.60%43.10%Ref.Ref.
  Below 442.57%2.19%0.99 [0.75;1.27]0.916
  65 and Above47.80%54.70%1.32 [1.22;1.42]<0.001
Gender:
  Male65.20%66.70%Ref.Ref.
  Female34.80%33.30%0.93 [0.86;1.01]0.085
Ethnicity:
  Caucasian77.00%74.50%Ref.Ref.
  African American10.90%13.20%1.25 [1.11;1.40]<0.001
  Hispanic5.96%6.33%1.10 [0.94;1.28]0.248
  Other6.14%5.90%0.99 [0.84;1.16]0.934
Insurance:
  Private47.00%34.20%Ref.Ref.
  Medicare42.00%53.20%1.74 [1.60;1.89]<0.001
  Medicaid5.39%7.56%1.93 [1.65;2.24]<0.001
  Workers' Compensation3.98%3.43%1.19 [0.95;1.46]0.123
  Other1.60%1.59%1.37 [0.99;1.84]0.054
Teaching status
  Teaching78.70%73.80%Ref.Ref.
  Non-teaching21.30%26.20%1.31 [1.20;1.42]<0.001
Hospital location
  Urban93.20%91.00%Ref.Ref.
  Rural6.83%9.05%1.36 [1.19;1.55]<0.001
Hospital size§
  Medium26.50%30.00%Ref.Ref.
  Large30.30%31.80%0.93 [0.84;1.02]0.116
  Small43.20%38.10%0.78 [0.71;0.85]<0.001
Surgeon volume
  Medium23.50%30.20%Ref.Ref.
  Very high38.70%32.00%0.64 [0.58;0.71]<0.001
  High35.10%33.50%0.74 [0.67;0.82]<0.001
  Low2.71%4.29%1.23 [1.00;1.50]0.046
Congestive heart failure2.91%7.00%2.51 [2.15;2.92]<0.001
Valvular disease4.40%6.29%1.46 [1.24;1.70]<0.001
Pulmonary circulation disorders0.93%1.77%1.93 [1.42;2.56]<0.001
Hypertension overall71.40%76.40%1.30 [1.19;1.42]<0.001
Diabetes overall27.00%34.10%1.40 [1.30;1.52]<0.001
Chronic renal failure3.86%7.14%1.92 [1.65;2.22]<0.001
Coagulopathy1.68%2.26%1.36 [1.04;1.74]0.024
Fluid electrolyte imbalance8.55%11.20%1.35 [1.20;1.52]<0.001
Deficiency anemia9.77%15.20%1.65 [1.48;1.83]<0.001
Psychoses0.39%1.03%2.66 [1.76;3.85]<0.001
Depression14.20%16.20%1.17 [1.05;1.29]0.004
OSA13.50%17.00%1.31 [1.18;1.44]<0.001

Risk-Adjusted Odds Ratio of 90 Day Non-elective Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without prior bariatric surgery (BS)

90 Day Readmission90 Day ReadmissionOR (95% CI)P-value*

NoYes
N=57769N=3968
Group:
  2 (+) Obesity (−) BS Prior to TJA97.60%97.40%Ref.Ref.
  1 (+) Obesity (+) BS Prior to TJA2.38%2.62%1.11 [0.90;1.35]0.334
Age group:
  Between 45 and 6449.80%42.50%Ref.Ref.
  Below 442.57%2.27%1.04 [0.83;1.28]0.747
  65 and Above47.70%55.20%1.36 [1.27;1.45]<0.001
Gender:
  Male65.10%66.60%Ref.Ref.
  Female34.90%33.40%0.94 [0.87;1.00]0.059
Ethnicity:
  Caucasian77.00%75.00%Ref.Ref.
  African American10.90%13.00%1.22 [1.11;1.34]<0.001
  Hispanic5.96%6.10%1.05 [0.91;1.20]0.483
  Other6.15%5.90%0.99 [0.86;1.13]0.829
Insurance:
  Private47.30%34.30%Ref.Ref.
  Medicare41.70%53.70%1.77 [1.65;1.90]<0.001
  Medicaid5.36%7.31%1.88 [1.64;2.14]<0.001
  Workers' Compensation4.01%3.07%1.06 [0.87;1.27]0.566
  Other1.60%1.61%1.39 [1.06;1.79]0.017
Teaching status
  Teaching78.80%73.50%Ref.Ref.
  Non-teaching21.20%26.50%1.34 [1.24;1.44]<0.001
Hospital location
  Urban93.20%90.70%Ref.Ref.
  Rural6.77%9.27%1.41 [1.26;1.57]<0.001
Hospital size§
  Medium26.40%30.10%Ref.Ref.
  Large30.30%31.90%0.92 [0.85;1.00]0.061
  Small43.30%38.00%0.77 [0.71;0.83]<0.001
Surgeon volume
  Medium23.30%30.20%Ref.Ref.
  Very high38.90%31.30%0.62 [0.57;0.68]<0.001
  High35.10%34.30%0.76 [0.70;0.82]<0.001
  Low2.68%4.21%1.22 [1.02;1.44]0.028
Congestive heart failure2.81%7.33%2.74 [2.40;3.11]<0.001
Valvular disease4.38%6.07%1.41 [1.23;1.61]<0.001
Pulmonary circulation disorders0.90%1.86%2.09 [1.62;2.65]<0.001
Hypertension overall71.30%76.50%1.31 [1.21;1.41]<0.001
Diabetes overall26.80%35.10%1.48 [1.38;1.58]<0.001
Chronic renal failure3.80%7.11%1.94 [1.70;2.20]<0.001
Coagulopathy1.68%2.14%1.29 [1.02;1.60]0.033
Fluid electrolyte imbalance8.53%10.70%1.28 [1.15;1.42]<0.001
Deficiency anemia9.69%14.70%1.61 [1.47;1.76]<0.001
Psychoses0.38%1.03%2.77 [1.95;3.82]<0.001
Depression14.10%16.40%1.19 [1.09;1.30]<0.001
OSA13.50%16.70%1.28 [1.18;1.40]<0.001

Risk-Adjusted Odds Ratio of 1 Year Non-elective Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without Prior Bariatric Surgery (BS)

1 Year Readmission1 Year ReadmissionOR (95% CI)P -value*

NoYes
N=54051N=7686
Group:
  2 (+) Obesity (−) BS Prior to TJA97.60%97.30%Ref.Ref.
  1 (+) Obesity (+) BS Prior to TJA2.36%2.67%1.14 [0.98;1.32]0.098
Age group:
  Between 45 and 6450.10%43.60%Ref.Ref.
  Below 442.57%2.42%1.08 [0.92;1.27]0.318
  65 and Above47.30%54.00%1.31 [1.25;1.38]<0.001
Gender:
  Male65.10%66.10%Ref.Ref.
  Female34.90%33.90%0.96 [0.91;1.01]0.094
Ethnicity:
  Caucasian77.00%75.60%Ref.Ref.
  African American10.80%12.50%1.18 [1.09;1.27]<0.001
  Hispanic5.95%6.12%1.05 [0.95;1.16]0.37
  Other6.18%5.78%0.95 [0.86;1.05]0.353
Insurance:
  Private48.10%34.70%Ref.Ref.
  Medicare41.10%52.60%1.77 [1.68;1.87]<0.001
  Medicaid5.22%7.36%1.95 [1.77;2.15]<0.001
  Workers' Compensation4.01%3.54%1.22 [1.07;1.39]0.004
  Other1.58%1.76%1.54 [1.27;1.85]<0.001
Teaching status
  Teaching79.10%74.20%Ref.Ref.
  Non-teaching20.90%25.80%1.31 [1.24;1.39]<0.001
Hospital location
  Urban93.30%91.20%Ref.Ref.
  Rural6.66%8.82%1.36 [1.24;1.48]<0.001
Hospital size§
  Medium26.20%29.70%Ref.Ref.
  Large30.20%31.70%0.93 [0.87;0.98]0.013
  Small43.60%38.60%0.78 [0.74;0.83]<0.001
Surgeon volume
  Medium23.10%28.50%Ref.Ref.
  Very high39.30%32.30%0.67 [0.63;0.71]<0.001
  High34.90%35.50%0.82 [0.77;0.88]<0.001
  Low2.65%3.68%1.13 [0.98;1.29]0.091
Congestive heart failure2.58%6.78%2.75 [2.48;3.05]<0.001
Valvular disease4.27%6.02%1.44 [1.30;1.59]<0.001
Pulmonary circulation disorders0.83%1.94%2.37 [1.96;2.85]<0.001
Hypertension overall70.90%77.10%1.39 [1.31;1.47]<0.001
Diabetes overall26.10%35.80%1.58 [1.50;1.66]<0.001
Chronic renal failure3.61%6.84%1.96 [1.77;2.17]<0.001
Coagulopathy1.67%1.99%1.20 [1.01;1.42]0.043
Fluid electrolyte imbalance8.46%10.10%1.22 [1.13;1.32]<0.001
Deficiency anemia9.49%13.70%1.52 [1.41;1.63]<0.001
Psychoses0.35%0.92%2.68 [2.02;3.50]<0.001
Depression13.80%17.40%1.32 [1.24;1.41]<0.001
OSA13.40%15.90%1.23 [1.15;1.31]<0.001

Risk-Adjusted Odds Ratio of 30 Day All-cause Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without prior bariatric surgery (BS), including elective TJA readmissions

30 Day Readmission30 Day ReadmissionOR (95% CI)P-value*

NoYes
N=58725N=3012
Group
  2 (+) Obesity (−) BS Prior to TJA97.60%96.80%Ref.Ref.
  1 (+) Obesity (+) BS Prior to TJA2.35%3.19%1.37 [1.10;1.68]0.005
Age group
  Between 45 and 6449.60%44.10%Ref.Ref.
  Below 442.56%2.22%0.98 [0.75;1.25]0.859
  65 and Above47.90%53.70%1.26 [1.17;1.36]<0.001
Gender
  Male34.80%33.60%Ref.Ref.
  Female65.20%66.40%1.05 [0.98;1.15]0.155
Ethnicity
  Caucasian77.00%74.20%Ref.Ref.
  African American10.90%13.10%1.25 [1.11;1.39]<0.001
  Hispanic5.93%6.84%1.20 [1.03;1.38]0.018
  Other6.15%5.84%0.99 [0.84;1.15]0.874
Insurance
  Private47.00%35.80%Ref.Ref.
  Medicare42.00%51.90%1.62 [1.50;1.76]<0.001
  Medicaid5.40%7.30%1.78 [1.53;2.06]<0.001
  Workers' Compensation3.98%3.45%1.14 [0.92;1.39]0.215
  Other1.60%1.56%1.28 [0.94;1.71]0.117
Teaching status
  Teaching78.70%73.50%Ref.Ref.
  Non-teaching21.30%26.50%1.34 [1.23;1.45]<0.001
Hospital location
  Urban93.20%91.30%Ref.Ref.
  Rural6.84%8.67%1.29 [1.13;1.47]<0.001
Hospital size§
  Medium26.50%29.20%Ref.Ref.
  Large30.30%31.60%0.95 [0.86;1.04]0.244
  Small43.10%39.10%0.82 [0.75;0.90]<0.001
Surgeon volume
  Medium23.50%29.50%Ref.Ref.
  Very high38.70%33.30%0.68 [0.62;0.75]<0.001
  High35.10%33.10%0.75 [0.68;0.82]<0.001
  Low2.71%4.13%1.21 [0.99;1.47]0.061
Congestive heart failure2.91%6.77%2.43 [2.08;2.81]<0.001
Valvular disease4.40%6.21%1.44 [1.23;1.67]<0.001
Pulmonary circulation disorders0.92%1.76%1.92 [1.43;2.53]<0.001
Hypertension overall71.40%76.20%1.28 [1.18;1.40]<0.001
Diabetes overall27.00%33.50%1.37 [1.26;1.48]<0.001
Chronic renal failure3.86%6.91%1.85 [1.59;2.13]<0.001
Coagulopathy1.68%2.29%1.38 [1.07;1.75]0.015
Fluid electrolyte imbalance8.56%10.90%1.31 [1.16;1.47]<0.001
Deficiency anemia9.75%15.20%1.66 [1.49;1.83]<0.001
Psychoses0.39%0.96%2.48 [1.65;3.60]<0.001
Depression14.20%16.00%1.16 [1.05;1.28]0.005
OSA13.50%16.90%1.30 [1.18;1.43]<0.001

Risk-Adjusted Odds Ratio of 90 Day All-cause Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without prior bariatric surgery (BS), including elective TJA readmissions

90 Day Readmission90 Day ReadmissionOR (95% CI)P -value*

NoYes
N=57218N=4519
Group:
  2 (+) Obesity (−) BS Prior to TJA97.70%96.90%Ref.Ref.
  1 (+) Obesity (+) BS Prior to TJA2.33%3.14%1.36 [1.13;1.61]0.001
Age group:
  Between 45 and 6449.70%44.40%Ref.Ref.
  Below 442.56%2.39%1.05 [0.85;1.27]0.663
  65 and Above47.70%53.20%1.25 [1.17;1.33]<0.001
Gender:
  Male34.80%33.90%Ref.Ref.
  Female65.20%66.10%1.04 [0.98;1.11]0.181
Ethnicity:
  Caucasian77.00%75.10%Ref.Ref.
  African American10.90%12.70%1.19 [1.09;1.31]<0.001
  Hispanic5.94%6.40%1.10 [0.97;1.25]0.126
  Other6.16%5.75%0.96 [0.84;1.09]0.511
Insurance:
  Private47.20%37.10%Ref.Ref.
  Medicare41.80%51.30%1.56 [1.46;1.67]<0.001
  Medicaid5.37%7.04%1.67 [1.47;1.89]<0.001
  Workers' Compensation4.03%2.94%0.93 [0.77;1.11]0.432
  Other1.60%1.62%1.29 [1.00;1.63]0.049
Teaching status
  Teaching78.90%73.20%Ref.Ref.
  Non-teaching21.10%26.80%1.36 [1.27;1.46]<0.001
Hospital location
  Urban93.20%91.30%Ref.Ref.
  Rural6.79%8.74%1.32 [1.18;1.46]<0.001
Hospital size§
  Medium26.40%29.70%Ref.Ref.
  Large30.30%31.30%0.92 [0.85;0.99]0.032
  Small43.30%38.90%0.80 [0.74;0.86]<0.001
Surgeon volume
  Medium23.40%29.10%Ref.Ref.
  Very high38.90%32.70%0.68 [0.62;0.73]<0.001
  High35.10%34.20%0.78 [0.72;0.84]<0.001
  Low2.69%3.95%1.18 [1.00;1.39]0.056
Congestive heart failure2.81%6.79%2.52 [2.22;2.86]<0.001
Valvular disease4.39%5.80%1.34 [1.17;1.53]<0.001
Pulmonary circulation disorders0.90%1.77%1.98 [1.55;2.50]<0.001
Hypertension overall71.30%76.30%1.29 [1.21;1.39]<0.001
Diabetes overall26.80%34.10%1.42 [1.33;1.51]<0.001
Chronic renal failure3.81%6.55%1.77 [1.56;2.00]<0.001
Coagulopathy1.68%2.06%1.23 [0.99;1.52]0.063
Fluid electrolyte imbalance8.53%10.40%1.24 [1.12;1.37]<0.001
Deficiency anemia9.67%14.40%1.57 [1.44;1.72]<0.001
Psychoses0.38%0.93%2.47 [1.75;3.41]<0.001
Depression14.10%16.50%1.20 [1.11;1.31]<0.001
OSA13.50%16.50%1.27 [1.17;1.38]<0.001

Risk-Adjusted Odds Ratio of 1 Year All-cause Readmissions for Obese Patients Undergoing Total Joint Arthroplasty Procedures (TJA) with and without prior bariatric surgery (BS), including elective TJA readmissions

1 Year Readmission1 Year ReadmissionOR (95% CI)P -value*

NoYes
N=51822N=9915
Group:
  2 (+) Obesity (−) BS Prior to TJA97.80%96.60%Ref.Ref.
  1 (+) Obesity (+) BS Prior to TJA2.21%3.37%1.54 [1.36;1.75]<0.001
Age group:
  Between 45 and 6450.00%45.80%Ref.Ref.
  Below 442.58%2.39%1.01 [0.88;1.17]0.853
  65 and Above47.40%51.90%1.19 [1.14;1.25]<0.001
Gender:
  Male35.10%32.90%Ref.Ref.
  Female64.90%67.10%1.10 [1.05;1.15]<0.001
Ethnicity:
  Caucasian77.00%75.90%Ref.Ref.
  African American10.80%12.10%1.14 [1.06;1.22]<0.001
  Hispanic5.93%6.20%1.06 [0.97;1.16]0.195
  Other6.21%5.72%0.93 [0.85;1.02]0.149
Insurance:
  Private48.00%38.20%Ref.Ref.
  Medicare41.10%49.80%1.52 [1.45;1.59]<0.001
  Medicaid5.19%7.04%1.70 [1.56;1.86]<0.001
  Workers' Compensation4.09%3.24%1.00 [0.88;1.12]0.938
  Other1.58%1.71%1.36 [1.15;1.61]<0.001
Teaching status
  Teaching79.20%74.70%Ref.Ref.
  Non-teaching20.80%25.30%1.29 [1.22;1.35]<0.001
  Hospital location
  Urban93.30%91.90%Ref.Ref.
  Rural6.71%8.10%1.23 [1.13;1.33]<0.001
Hospital size§
  Medium26.10%29.60%Ref.Ref.
  Large30.30%30.90%0.90 [0.85;0.95]<0.001
  Small43.60%39.40%0.80 [0.76;0.84]<0.001
Surgeon volume
  Medium23.10%27.40%Ref.Ref.
  Very high39.30%33.90%0.72 [0.69;0.77]<0.001
  High35.00%35.30%0.85 [0.80;0.90]<0.001
  Low2.67%3.38%1.07 [0.94;1.21]0.327
Congestive heart failure2.57%5.84%2.35 [2.12;2.59]<0.001
Valvular disease4.27%5.64%1.34 [1.22;1.47]<0.001
Pulmonary circulation disorders0.84%1.63%1.97 [1.64;2.35]<0.001
Hypertension overall70.70%76.60%1.36 [1.29;1.43]<0.001
Diabetes overall26.10%33.80%1.45 [1.38;1.51]<0.001
Chronic renal failure3.64%5.97%1.68 [1.53;1.85]<0.001
Coagulopathy1.68%1.82%1.08 [0.92;1.27]0.356
Fluid electrolyte imbalance8.50%9.56%1.14 [1.06;1.22]0.001
Deficiency anemia9.45%13.00%1.43 [1.34;1.53]<0.001
Psychoses0.36%0.75%2.10 [1.59;2.74]<0.001
Depression13.80%16.90%1.28 [1.21;1.35]<0.001
OSA13.40%15.30%1.18 [1.11;1.25]<0.001
Authors

The authors are from the Department of Orthopaedic Surgery, NYU Langone Medical Center, Hospital for Joint Diseases, New York, New York.

Dr Liu, Mr Paoli, Dr Mahure, and Dr Campbell have no relevant financial relationships to disclose. Dr Bosco is a paid consultant for Medtronic, Pacira, Surgical Directions, and Labrador Healthcare Consultants and receives royalties from Genovel and Responsive Risk Solutions.

Correspondence should be addressed to: James X. Liu, MD, Department of Orthopaedic Surgery, NYU Langone Medical Center, Hospital for Joint Diseases, 301 E 17th St, Ste 1400, New York, NY 10003 ( James.Liu@nyumc.org).

Received: August 07, 2017
Accepted: January 10, 2018
Posted Online: March 02, 2018

10.3928/01477447-20180226-02

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