For the HbA1c < 8% eligibility criterion, non-Hispanic blacks and individuals of lower socioeconomic status were less likely to be eligible than non-Hispanic whites and individuals of higher socioeconomic status, respectively (Table 2). The ORs for the HbA1c < 8% criterion were as follows: odds of eligibility for non-Hispanic blacks were 56% lower (OR, 0.44; 95% CI, 0.37–0.53; p < 0.001) and 59% lower for Hispanics (OR, 0.41; 95% CI; 0.33–0.51; p < 0.001) compared with non-Hispanic whites. Odds of eligibility for women were 51% higher than for men (OR, 1.51; 95% CI, 1.28–1.78; p < 0.001). Odds of eligibility for individuals with an annual household income < USD 45,000 were 34% lower than those with an annual income ≥ USD 45,000 (OR, 0.73; 95% CI, 0.56–0.94; p = 0.008), and odds for individuals with a high school degree or less were 42% lower than those with a degree greater than a high school degree (OR, 0.58; 95% CI, 0.44–0.77; p < 0.001).
When using the nonsmoker criterion, odds of eligibility for non-Hispanic blacks were 18% lower than for non-Hispanic whites (OR, 0.84; 95% CI, 0.73–0.97; p = 0.019). Odds of eligibility for individuals with an annual household income < USD 45,000 were 47% lower than those with income ≥ USD 45,000 (OR, 0.53; 95% CI, 0.47–0.61; p < 0.001), and odds for individuals with a high school degree or less were 71% lower than those with a degree beyond a high school degree (OR, 0.29; 95% CI, 0.24–0.35; p < 0.001). Conversely, odds of eligibility for Hispanics were 65% higher than for non-Hispanic whites (OR, 1.65; 95% CI, 1.37–1.98; p < 0.001), and odds for women were 44% higher than for men (OR, 1.44; 95% CI, 1.27–1.63; p < 0.001).
Additional analyses that do not control for additional factors (including age and socioeconomic status) but that show the proportions of each subpopulation that would be affected by inflexible eligibility criteria were run for reference (Appendix Table, Supplemental Digital Content).
More than one million hip and knee arthroplasties are performed in the United States each year, increasing function and quality of life . The number of these procedures performed annually continues to rise  as do concerns about disparities in utilization by race-ethnicity, gender, and socioeconomic status [31, 37, 38, 45]. Lower extremity arthroplasty has been a prime target for beginning to transition medical care in the United States from a fee-for-service model to bundled payments or pay-for-performance models. These payment structures encourage avoidance of higher risk patients, sometimes by using inflexible eligibility criteria. The impact of inflexible eligibility criteria on racial-ethnic, gender-based, and socioeconomic disparities in lower extremity arthroplasty has been discussed but not quantified [3, 4, 16, 17]. We found that inflexible cutoffs related to BMI, HbA1c, and smoking status would substantially restrict access to lower extremity arthroplasty for non-Hispanic blacks, Hispanics, women, and individuals of lower socioeconomic status. Theoretically, removal of disparities in BMI, HbA1c, and smoking would prevent inflexible eligibility criteria from worsening disparities in lower extremity arthroplasty. However, obesity, diabetes, and smoking are complex issues intertwined with economic, social, cultural, and personal factors, and addressing these disparities is a long-term public health goal, unlikely to be eliminated in the near future. Exclusion criteria eliminate considerations of patient choice, substituting medical risk factors (such as BMI, HbA1c, smoking) for a patient-physician conversation about risks and benefits. Inflexible eligibility criteria would affect racial minorities, women, and individuals of lower socioeconomic status more than they affect non-Hispanic whites, men, and individuals of higher socioeconomic status, and therefore they raise concerns about discrimination and justice.
The main limitation of our study is that the database is not limited to patients with indications for lower extremity arthroplasty. Our model examines how eligibility would be affected, assuming that everyone would benefit from and may consider undergoing hip or knee arthroplasty. Although actual reductions in arthroplasty eligibility as a result of these criteria may differ by subpopulation, this model highlights how inflexible eligibility criteria may be a powerful source of decreased access for racial minorities, women, and individuals of lower socioeconomic status. Additionally, our model examined individual eligibility criteria. Although patients may have more than one risk factor at a time (for example, both obesity and smoking), we analyzed individual risk factors because failure to meet only one eligibility criterion is enough to prevent eligibility. NHANES also excludes persons in supervised care or custody in institutional settings as well as active-duty military personnel. Our results are not generalizable to these populations. We were missing data on some ethnic groups such as Asians, so we were unable to estimate the effects of eligibility criteria on these groups. Data on race-ethnicity, smoking status, educational level, and income were self-reported. The issue of self-reported race-ethnicity is especially complex. Race-ethnicity is both genetic and a social construct that may be a proxy for other factors that affect health such as socioeconomic status, level of social support, and healthcare access; by contrast, the genetics of race may also influence the frequency and severity of disease in some instances. It can be very difficult to tell when race and ethnicity are proxies or confounding variables and when they actually exert a biologic influence on health . We assessed some of the relationship between socioeconomic factors and inflexible eligibility criteria through two commonly used measures: income and education, yet social support and healthcare access are complex issues, of which education and income can provide only a limited picture. Self-reported smoking status may also be particularly prone to social desirability bias . Lastly, although we examined only three characteristics (race-ethnicity, gender, socioeconomic status) as they relate to arthroplasty eligibility, other factors such as insurance status, health status, and occupation also influence arthroplasty access and indications. These factors may, in turn, shape subgroup rates of eligibility for arthroplasty.
Our BMI findings are mostly consistent with those of a substantial body of evidence documenting disparities by race-ethnicity, gender, and socioeconomic status [1, 11-13, 19-21, 27, 35, 39-41]. Non-Hispanic black adults, women, and individuals of lower socioeconomic status have higher rates of obesity than non-Hispanic whites, men, and individuals of higher socioeconomic status . Our finding of increased eligibility among Hispanics compared with non-Hispanic whites differs with documented Hispanic-white disparities in obesity . One reason for this difference may be that our analysis also adjusted for age, gender, and socioeconomic status, whereas prior studies did not account for socioeconomic status and used different age ranges [32, 34, 42]. The exact relationships among age, gender, race-ethnicity, and socioeconomic status are complex and not fully understood, but socioeconomic status and age likely are confounding factors in the relationship between Hispanic ethnicity and obesity and may explain the differences between our findings and those of previous studies [25, 32, 34]. These BMI findings have important implications. First, BMI is difficult to modify. Enrollment in preoperative weight loss programs has produced weight loss in only 51% of patients, and even then, the weight loss is slight (averaging only 0.1 lbs) . Additionally, a BMI of 36 is a far different risk factor compared with a BMI of 46. In light of this, patients require knowledge of their surgical risk as it relates to their BMI to make informed decisions. However, inflexible eligibility criteria based on BMI prevent individuals from making decisions about hip or knee arthroplasty on the basis of their value systems. Individuals may decide that the functional benefits of hip or knee arthroplasty outweigh the increased surgical risks associated with their BMI, and our ability to predict personal preferences is limited because such preferences often differ by race-ethnicity, gender, and socioeconomic status . Patients who are ineligible because of inflexible criteria based on BMI would lose the ability to exercise their decision-making capacity, and thus their autonomy would be compromised. Our study shows that non-Hispanic blacks, women, and those of lower socioeconomic status would be more likely to experience such a loss of autonomy than non-Hispanic whites, men, or those of higher socioeconomic status.
Our HbA1c findings are consistent with evidence on disparities related to diabetes. Studies have documented a higher prevalence of diabetes among non-Hispanic blacks and Hispanics versus whites, men versus women , and among individuals of lower socioeconomic status versus those of higher socioeconomic status . An HbA1c level > 8% is a critical, modifiable risk factor for surgical complications and is often associated with poor support, lack of confidence in following through with treatment plans, and greater financial barriers . All of these factors also represent potential threats to the success of hip or knee arthroplasty. However, the achievability of a goal must also be considered. It has been shown that 70% of patients can obtain an HbA1c level < 8% . Given the high surgical risks associated with an HbA1c level > 8%, we do not advocate removing this eligibility criterion, and we support physicians partnering with their patients in preoperative optimization of glycemic control. Furthermore, we believe that the principle of justice requires physicians to understand and help address, when possible, the existing disparities in diabetes care.
Our findings regarding smoking status also support recent studies showing that men are more likely to smoke than women, non-Hispanic whites are more likely to smoke than Hispanics, and individuals of lower socioeconomic status are more likely to smoke than those of higher socioeconomic status . Given that smoking cessation rates at 6 months are below 10% , inflexible eligibility criteria based on smoking status may cause permanent ineligibility for hip or knee arthroplasty. Although not definitive, current studies suggest that smoking risk for arthroplasty is dose-dependent [36, 41]. Therefore, we believe that shared decision-making regarding reduced or eliminated smoking around the time of surgery should be patient-specific rather than treated as an inflexible eligibility criterion.
In summary, novel payment structures may reduce healthcare costs, but they also encourage the use of inflexible eligibility criteria based on surgical risk factors. Surgeons should be aware that policies with inflexible eligibility criteria decrease access to lower extremity arthroplasty in vulnerable, often-discriminated-against populations such as non-Hispanic blacks, Hispanics, women, and individuals of lower socioeconomic status. Our findings emphasize that payment models should include greater stratification of risk factors such as BMI, HbA1c, and smoking pack-years. Increasing the number of stratified levels would reduce the incentive to avoid patients with higher BMI, higher HbA1c level, or current smokers without removing the benefits of a cost-conscious reimbursement system.
We thank Rachel Box, Eileen Martin, and Jenni Weems for their assistance in editing this publication.
1. A Workgroup of the American Association of Hip and Knee Surgeons (AAHKS) Evidence Based Committee. Obesity and total joint arthroplasty: a literature based review. J Arthroplasty. 2013;28:714–721.
2. Altieri MS, Tuppo C, Telem DA, Herlihy D, Cottell K, Pryor AD. Predictors of a successful medical weight loss program. Surg Obes Relat Dis. 2015;11:431–435.
3. Bronson WH, Fewer M, Godlewski K, Slover JD, Caplan A, Iorio R, Bosco J. The ethics of patient risk modification prior to elective joint replacement surgery. J Bone Joint Surg Am. 2014;96:e113.
4. Casalino LP, Elster A, Eisenberg A, Lewis E, Montgomery J, Ramos D. Will pay-for-performance and quality reporting affect health care disparities? Health Aff (Millwood). 2007;26:w405–414.
8. Connolly V, Unwin N, Sherriff P, Bilous R, Kelly W. Diabetes prevalence and socioeconomic status: a population based study showing increased prevalence of type 2 diabetes mellitus in deprived areas. J Epidemiol Community Health. 2000;54:173–177.
9. Connor Gorber S, Schofield-Hurwitz S, Hardt J, Levasseur G, Tremblay M. The accuracy of self-reported smoking: a systematic review of the relationship between self-reported and cotinine-assessed smoking status. Nicotine Tob Res. 2009;11:12–24.
11. Duchman KR, Gao Y, Pugely AJ, Martin CT, Noiseux NO, Callaghan JJ. The effect of smoking on short-term complications following total hip and knee arthroplasty. J Bone Joint Surg Am. 2015;97:1049–1058.
12. Everhart JS, Altneu E, Calhoun JH. Medical comorbidities are independent preoperative risk factors for surgical infection after total joint arthroplasty. Clin Orthop Relat Res. 2013;471:3112–3119.
13. Foran JR, Mont MA, Rajadhyaksha AD, Jones LC, Etienne G, Hungerford DS. Total knee arthroplasty in obese patients: a comparison with a matched control group. J Arthroplasty. 2004;19:817–824.
14. Giori NJ, Ellerbe LS, Bowe T, Gupta S, Harris AH. Many diabetic total joint arthroplasty candidates are unable to achieve a preoperative hemoglobin A1c goal of 7% or less. J Bone Joint Surg Am. 2014;96:500–504.
15. Han HS, Kang SB. Relations between long-term glycemic control and postoperative wound and infectious complications after total knee arthroplasty in type 2 diabetics. Clin Orthop Surg. 2013;5:118–123.
16. Humbyrd CJ. The ethics of bundled payments in total joint replacement: ‘cherry picking’ and ‘lemon dropping.’ J Clin Ethics. 2018;28:62–68.
17. Ibrahim SA, Kim H, McConnell KJ. The CMS comprehensive care model and racial disparity in joint replacement. JAMA. 2016;316:1258–1259.
18. Jamal A, King BA, Neff LJ, Whitmill J, Babb SD, Graffunder CM. Current cigarette smoking among adults—United States, 2005-2015. MMWR Morb Mortal Wkly Rep. 2016;65:1205–1211.
19. Jameson SS, Mason JM, Baker PN, Elson DW, Deehan DJ, Reed MR. The impact of body mass index on patient reported outcome measures (PROMs) and complications following primary hip arthroplasty. J Arthroplasty. 2014;29:1889–1898.
20. Kapadia BH, Issa K, Pivec R, Bonutti PM, Mont MA. Tobacco use may be associated with increased revision and complication rates following total hip arthroplasty. J Arthroplasty. 2014;29:777–780.
21. Keswani A, Lovy AJ, Robinson J, Levy R, Chen D, Moucha CS. Risk factors predict increased length of stay and readmission rates in revision joint arthroplasty. J Arthroplasty. 2016;31:603–608.
23. Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Joint Surg Am. 2007;89:780–785.
24. Kurtz SM, Lau E, Ong K, Zhao K, Kelly M, Bozic KJ. Future young patient demand for primary and revision joint replacement: national projections from 2010 to 2030. Clin Orthop Relat Res. 2009;467:2606–2612.
25. LaVeist TA. Disentangling race and socioeconomic status: a key to understanding health inequalities. J Urban Health. 2005;82:iii26–34.
26. Leopold SS, Beadling L, Calabro AM, Dobbs MB, Gebhardt MC, Gioe TJ, Manner PA, Porcher R, Rimnac CM, Wongworawat MD. Editorial: The complexity of reporting race and ethnicity in orthopaedic research. Clin Orthop Relat Res. 2018;476:917–920.
27. Marchant MH Jr, Viens NA, Cook C, Vail TP, Bolognesi MP. The impact of glycemic control and diabetes mellitus on perioperative outcomes after total joint arthroplasty. J Bone Joint Surg Am. 2009;91:1621–1629.
28. McBrien KA, Naugler C, Ivers N, Weaver RG, Campbell D, Desveaux L, Hemmelgarn BR, Edwards AL, Saad N, Nicholas D, Manns BJ. Barriers to care in patients with diabetes and poor glycemic control—a cross-sectional survey. PLoS One. 2017;12:e0176135.
29. Messer K, Trinidad DR, Al-Delaimy WK, Pierce JP. Smoking cessation rates in the United States: a comparison of young adult and older smokers. Am J Public Health. 2008;98:317–322.
30. Mota RE, Tarricone R, Ciani O, Bridges JF, Drummond M. Determinants of demand for total hip and knee arthroplasty: a systematic literature review. BMC Health Serv Res. 2012;12:225.
31. O'Connor MI, Hooten EG. Breakout session: Gender disparities in knee osteoarthritis and TKA. Clin Orthop Relat Res. 2011;469:1883–1885.
32. Ogden CL, Carroll MD, Kit BK, Flegal KM. Prevalence of childhood and adult obesity in the United States, 2011-2012. JAMA. 2014;311:806–814.
33. Ong KL, Mowat FS, Chan N, Lau E, Halpern MT, Kurtz SM. Economic burden of revision hip and knee arthroplasty in Medicare enrollees. Clin Orthop Relat Res. 2006;446:22–28.
34. Paeratakul S, Lovejoy JC, Ryan DH, Bray GA. The relation of gender, race and socioeconomic status to obesity and obesity comorbidities in a sample of US adults. Int J Obes Relat Metab Disord. 2002;26:1205–1210.
35. Pedersen AB, Mehnert F, Johnsen SP, Sorensen HT. Risk of revision of a total hip replacement in patients with diabetes mellitus: a population-based follow up study. J Bone Joint Surg Br. 2010;92:929–934.
36. Sadr Azodi O, Bellocco R, Eriksson K, Adami J. The impact of tobacco use and body mass index on the length of stay in hospital and the risk of post-operative complications among patients undergoing total hip replacement. J Bone Joint Surg Br. 2006;88:1316–1320.
37. Singh JA, Lu X, Rosenthal GE, Ibrahim S, Cram P. Racial disparities in knee and hip total joint arthroplasty: an 18-year analysis of national Medicare data. Ann Rheum Dis. 2014;73:2107–2115.
38. Skinner J, Zhou W, Weinstein J. The influence of income and race on total knee arthroplasty in the United States. J Bone Joint Surg Am. 2006;88:2159–2166.
39. Spicer DDM, Pomeroy DL, Badenhausen WE Jr, Schaper LA, Curry JI, Suthers KE, Smith MW. Body mass index as a predictor of outcome in total knee replacement. Int Orthop. 2001;25:246–249.
40. Stryker LS, Abdel MP, Morrey ME, Morrow MM, Kor DJ, Morrey BF. Elevated postoperative blood glucose and preoperative hemoglobin A1C are associated with increased wound complications following total joint arthroplasty. J Bone Joint Surg Am. 2013;95:808–814, s801-802.
41. Tischler EH, Matsen Ko L, Chen AF, Maltenfort MG, Schroeder J, Austin MS. Smoking increases the rate of reoperation for infection within 90 days after primary total joint arthroplasty. J Bone Joint Surg Am. 2017;99:295–304.
42. Wang Y, Beydoun MA. The obesity epidemic in the United States—gender, age, socioeconomic, racial/ethnic, and geographic characteristics: a systematic review and meta-regression analysis. Epidemiol Rev. 2007;29:6–28.
43. Ward DT, Metz LN, Horst PK, Kim HT, Kuo AC. Complications of morbid obesity in total joint arthroplasty: risk stratification based on BMI. J Arthroplasty. 2015;30:42–46.
44. Yu S, Garvin KL, Healy WL, Pellegrini VD Jr, Iorio R. Preventing hospital readmissions and limiting the complications associated with total joint arthroplasty. J Am Acad Orthop Surg. 2015;23:e60–71.
© 2018 Lippincott Williams & Wilkins LWW
45. Zhang W, Lyman S, Boutin-Foster C, Parks ML, Pan TJ, Lan A, Ma Y. Racial and ethnic disparities in utilization rate, hospital volume, and perioperative outcomes after total knee arthroplasty. J Bone Joint Surg Am. 2016;98:1243–1252.