The Journal of Arthroplasty xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Social and Behavioral Factors in Total Knee and Hip Arthroplasty Hilal Maradit Kremers, MD, MSc a,b, Walter K. Kremers, PhD a, Daniel J. Berry, MD b, David G. Lewallen, MD b a b
Department of Health Sciences Research Mayo Clinic, Rochester, Minnesota Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota
a r t i c l e
i n f o
Article history: Received 12 February 2015 Accepted 28 April 2015 Available online xxxx Keywords: arthroplasty socioeconomic factors smoking alcohol marital status education
a b s t r a c t Social and behavioral factors are important determinants of health outcomes in a number of medical conditions but their role in joint arthroplasty is poorly understood. In a cohort of 20,124 hip and knee arthroplasty procedures, smoking was associated with a significantly higher risk of surgical site infections (hazard ratio 1.7, 95% CI: 1.1–2.6), whereas alcohol use was associated with a lower risk of reoperations and revisions (hazard ratio 0.7, 95% CI: 0.5–0.8). There was no association between marital status and educational attainment with the risk of complications or reoperations in total hip and knee arthroplasty. © 2015 Elsevier Inc. All rights reserved.
Social and behavioral factors are important determinants of health outcomes in a number of medical conditions but their role in total hip (THA) and knee (TKA) arthroplasty is poorly understood. In studies of patient-reported outcomes, married patients and those with a higher education level have better functional outcomes than patients who are single or with low education levels [1–4]. This has been attributed to better social support and coping skills and improved ability to process and apply medical information. Yet, better patient-reported outcomes may not necessarily translate into fewer complications or fewer revision surgeries. For example, TKA patients from communities with the highest education level in New York and California have a higher risk of revision surgery [5], a finding that has been attributed to higher likelihood of well-educated patients to return and seek follow-up care. Among the behavioral factors, smoking is perhaps the best-studied risk factor in THA and TKA [6–10]. Although the adverse effects of smoking around the time of surgery are well-documented, studies in THA and TKA were mostly small, underpowered and lacked long-term follow-up [8]. Similarly, the effects of alcohol consumption on arthroplasty outcomes are poorly understood [7,11,12]. With this background, our objective was to assess the long-term risk of complications, revisions and mortality associated with patients’ marital status, education level, smoking and alcohol use in TKA and THA.
No author associated with this paper has disclosed any potential or pertinent conflicts which may be perceived to have impending conflict with this work. For full disclosure statements refer to doi: http://dx.doi.org/10.1016/j.arth.2015.04.032. Reprint requests: Hilal Maradit Kremers, MD, MSc, 200 First Street SW, Harwick 6-69, Rochester, MN, 55905.
Material and Methods The study comprised 15,890 adult patients (≥ 18 years) who underwent 20,124 primary and revision TKA and THA procedures at a single tertiary care institution in the United States between 1/1/2002 and 12/31/2009. Revision procedures performed for infected joint arthroplasties were excluded. Information on demographics, surgical characteristics (i.e., surgery type, indications, prior surgeries on the joint, ASA score, procedure duration), body mass index (BMI), diabetes mellitus and arthroplasty outcomes (dates and types of complications within the first year, reoperations, revisions, death) were ascertained through the institutional joint registry, as previously described [13,14]. Briefly, baseline and follow-up data collection is performed by trained registry staff using pre-defined data collection forms and standard operating procedures. All patients are followed up by the surgeon at least twice in the first postsurgical year, in years 2 and 5 and at 5-year intervals thereafter in order to ascertain various arthroplasty outcomes, including details of revision surgeries. If in-person follow-up examination at the clinic is not possible, patients are contacted by letter and/or telephone and asked to complete a standardized data collection form which includes information on complications, reoperations and revisions. The overall clinical follow-up is excellent with more than 65% complete at 30 years. Information on marital status, education, smoking and alcohol use was retrieved from the patient-provided forms stored as part of the patients’ electronic medical records. Marital status was defined based on patients’ responses to their relationship status at the time of surgery (i.e., married, widowed, divorced, single, committed relationship). Education level was categorized under 6 categories based on patients’ report of the highest grade of school that they had completed. Smoking status was classified as current, former or never based on patients’ responses to questions on current and past
http://dx.doi.org/10.1016/j.arth.2015.04.032 0883-5403/© 2015 Elsevier Inc. All rights reserved.
Please cite this article as: Maradit Kremers H, et al, Social and Behavioral Factors in Total Knee and Hip Arthroplasty, J Arthroplasty (2015), http:// dx.doi.org/10.1016/j.arth.2015.04.032
2
H. Maradit Kremers et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx
smoking history. Alcohol use was defined based on patients’ response to 2 questions related to alcohol use: “Have you ever felt the need to cut down on your alcohol consumption?” and “Do relatives/friends worry or complain about your alcohol consumption?” Patient-provided information was missing in roughly 30% of procedures performed during the study time window. Multivariable Cox proportional hazard models were used to estimate hazard ratios (HRs) for each risk factor adjusting for age, gender, BMI, calendar year, surgery type, number of prior surgery on same joint, diabetes status, ASA score and procedure duration. Patients with missing data were treated as a separate category. We examined 5 different outcomes: surgical site infections and overall complications (including implant loosening, instability, dislocation, bone or implant fractures, vascular, neurological, soft tissue, alignment, wound problems, thrombovascular events, patellar complications, osteolysis) within the 12-month window following surgery, reoperations and revisions at any time during follow-up and death. A robust sandwich covariance estimator was used to correct for within-subject correlation for those with multiple surgeries.
Results The study cohort included 10,438 TKA and 9688 THA procedures of which 20% were revision surgeries. Mean age was 66.3 years and 45% were male. At the time of surgery, a majority of patients (53%) reported being married (Table 1). About a third of patients were high school graduate or less and about a quarter had four or more years of college or post-graduate education. At the time of surgery, only 5% were current, 26% were former smokers. Thirteen percent answered yes to one of the two questions related to alcohol use. In multivariate Cox regression models, we observed no relationship between marital status and educational attainment and the risk of surgical site infections, complications, reoperations or revisions (Table 1). Current smoking was associated with a significantly higher risk of surgical site infections (HR: 1.7, 95% CI: 1.1–2.6), but not the overall risk of complications, reoperations or revisions. Alcohol use was associated with a significantly lower risk of reoperations and revision surgeries (HR: 0.7, 95% CI: 0.5–0.8). Despite the lack of association with selected arthroplasty outcomes, marital status and educational
attainment were significant predictors of death, similar to the associations observed in the general population. Discussion We examined the role of selected patient-reported social and behavioral factors on arthroplasty outcomes in a contemporary cohort of patients who underwent THA and TKA surgery at a large tertiary care center in the United States. Our findings indicate that two nonclinical, non-modifiable social factors (education and marital status) are not associated with a higher risk of complications or reoperations. Current smokers have a higher risk of surgical site infections. Collectively, these findings indicate that, apart from efforts to discourage smoking, there is no evidence for implementation of different or intensive post-arthroplasty support strategies for patients who are single or of low education level. The mechanisms through which social and behavioral risk factors have an effect on health outcomes are complex and not always clear. Arthroplasty patients from low socioeconomic groups report worse preoperative pain and function, but seem to benefit equally from surgery [15,16]. Differences in socioeconomic composition, healthcare systems and socioeconomic measures across countries imply that the findings of some excellent studies are not always generalizable to other countries. Within the United States, there is growing recognition of sociodemographic disparities in outcomes of a number of conditions including THA and TKA [17], and such disparities recently triggered discussions on adjustment of quality measures for sociodemographic risk factors [18,19]. Yet, empirical evidence for disparities in clinical outcomes of arthroplasty is limited to race and insurance status [20]. We examined 2 important social factors (marital status and education) which are known to be associated with patient-reported outcomes in arthroplasty [1–4], and certainly influence post-discharge clinical outcomes in other chronic or acute conditions [19,21]. We found no evidence that marital status or education is associated with either a higher rate of complications or revisions in THA and TKA. Lack of associations with arthroplasty outcomes in this study may be in part attributable may be in part attributable to the elective nature of the THA and TKA hospitalizations as compared to acute hospitalizations for pneumonia or heart failure. Although one previous study reported a higher likelihood of revisions in communities with higher education levels [5], findings are not easily comparable because we relied on individual-
Table 1 Risk of Selected Outcomes Associated with Social and Behavioral Risk Factors in a Cohort of 20124 THA and TKA Procedures. Hazard Ratio (95% Confidence Intervals)a
Marital status Married Divorced/widowed Single missing Education 8th grade or less Some high school High school graduate Some college 4-year college graduate Post-graduate missing Smoking Never Former Current missing Alcohol use No Yes missing
N (%)
Surgical Site Infections
Any Complication
Reoperation
Revision
Death
10,584 (53%) 2809 (14%) 756 (4%) 5975 (30%)
1 (ref) 1.1 (0.8–1.5) 1.0 (0.6–1.8) 1.2 (0.5–2.7)
1 (ref) 1.1 (1.0–1.2) 1.0 (0.9–1.2) 1.0 (0.8–1.3)
1 (ref) 1.1 (0.9–1.3) 0.9 (0.7–1.2) 1.1 (0.7–1.6)
1 (ref) 1.0 (0.7–1.2) 0.8 (0.6–1.2) 1.1 (0.7–1.9)
1 (ref) 1.2 (1.1–1.4) 1.6 (1.3–1.9) 2.8 (2.0–3.9)
638 (3%) 670 (3%) 4884 (24%) 3430 (17%) 1919 (10%) 2670 (13%) 5913 (29%)
0.8 (0.4–1.6) 0.9 (0.5–1.8) 1 (ref) 1.0 (0.7–1.4) 1.3 (0.9–2.0) 0.8 (0.5–1.3) 0.9 (0.6–1.4)
1.0 (0.9–1.2) 1.0 (0.8–1.1) 1 (ref) 1.0 (0.8–1.1) 1.0 (0.9–1.1) 1.0 (0.9–1.1) 1.2 (0.9–1.5)
1.1 (0.8–1.4) 1.0 (0.8–1.3) 1 (ref) 0.9 (0.8–1.1) 0.9 (0.8–1.1) 1.0 (0.8–1.1) 1.0 (0.7–1.6)
1.0 (0.7–1.6) 0.9 (0.6–1.4) 1 (ref) 0.9 (0.7–1.1) 1.0 (0.7–1.3) 1.1 (0.9–1.3) 0.8 (0.5–1.6)
1.2 (1.1–1.5) 1.0 (0.8–1.2) 1 (ref) 0.9 (0.8–1.1) 0.8 (0.7–0.9) 0.7 (0.6–0.8) 0.8 (0.6–1.3)
7678 (38%) 5325 (26%) 951 (5%) 6170 (31%)
1 (ref) 1.0 (0.8–1.3) 1.7 (1.1–2.6) 1.5 (0.6–3.7)
1 (ref) 1.0 (0.9–1.1) 1.0 (0.9–1.2) 0.8 (0.6–1.1)
1(ref) 1.0 (0.9–1.1) 1.1 (0.9–1.4) 1.1 (0.7–1.7)
1(ref) 1.1 (0.9–1.3) 1.2 (0.9–1.6) 0.7 (0.3–1.4)
1(ref) 1.2 (1.1–1.3) 2.2 (1.8–2.6) 1.9 (1.3–2.8)
11614 (58%) 2691 (13%) 5819 (29%)
1 (ref) 0.7 (0.5–1.0) 0.7 (0.2–2.2)
1 (ref) 0.9 (0.8–1.0) 1.0 (0.7–1.3)
1 (ref) 0.8 (0.7–0.9) 0.8 (0.4–1.3)
1 (ref) 0.7 (0.5–0.8) 1.5 (0.7–3.3)
1 (ref) 1.0 (0.9–1.2) 0.9 (0.7–1.2)
a Estimates from multivariable Cox regression models adjusting for age, gender, BMI, calendar year, prior surgery, prior TJA, diabetes, ASA score, procedure time, alcohol, smoking, education, marital status.
Please cite this article as: Maradit Kremers H, et al, Social and Behavioral Factors in Total Knee and Hip Arthroplasty, J Arthroplasty (2015), http:// dx.doi.org/10.1016/j.arth.2015.04.032
H. Maradit Kremers et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx
level education status as compared to the community-level measures in the previous study. Our findings with smoking are in line a recent systematic review [8] that reported a higher risk of infection, other complications, and mortality among smokers. Yet, we found no evidence for an association between smoking and the risk of revision surgery. This is in contrast to at least two small studies [22,23] which suggested that smoking may be associated with increased risk of aseptic loosening due to delayed bone healing and bone regeneration. Furthermore, although our measure of alcohol use was rather crude, we observed a significantly lower risk of revisions among patients who were at least moderate drinkers. The reasons for this are unclear, but this was previously suggested in some reports [11,12]. Further studies with more sensitive measures of smoking history and alcohol use are warranted to examine their effects in THA and TKA patients. Due to the retrospective design and reliance on patient-reported data collected for clinical purposes, data on risk factors were missing in about 30% of procedures (i.e., forms were not completed by patients). Age was the main determinant of missingness where a higher percentage of young patients had missing patient-provided forms (i.e., N 50% in patients 40 years and younger versus 20% in patients N 70 years of age). Instead of excluding patients with missing data from the analyses, we instead examined them as a separate category. We found a lack of any association in patients with missing data suggesting that missingness was probably random and not associated with the risk of outcomes. We further examined mortality as a separate outcome to validate the population-level risk factor associations. Our outcome measures were limited to arthroplasty-related clinical outcomes. Education and marital status are only two of many measures of socioeconomic status which may be more directly related to clinical outcomes, such as income, insurance, housing situation, urban–rural location or proximity to hospital. Furthermore, although we failed to identify associations with selected clinical outcomes, these risk factors may still be associated with other arthroplasty outcomes such as the range of motion, patient satisfaction, ability to walk without assistive device, degree of residual pain, or ability to return to full activities, discharge disposition or readmissions. Our measures of smoking status and alcohol use are also not sensitive enough to examine dose response relationships as we had no information on the amount of smoking or alcohol use. There are few objective measures of alcohol use and patients typically under-report their use. The alcohol use questions in this study are vague and likely may have been answered in the negative by some heavy users. Therefore, our findings with alcohol use need to be interpreted with caution. The unique strengths of our study are availability of both short and longterm outcome data available through an institutional joint registry, unique ability to link registry data with medical records and ability to adjust for several clinically important confounders. In conclusion, there is a need to address the social and behavioral determinants of long-term outcomes in THA and TKA. Our findings indicate that these procedures may differ from other conditions and the
3
findings of this study suggest that marital status or educational level do not necessarily put arthroplasty candidates at a disadvantage for complications or revisions. References 1. Bischoff-Ferrari HA, Lingard EA, Losina E, et al. Psychosocial and geriatric correlates of functional status after total hip replacement. Arthritis Rheum 2004;51(5):829. 2. Schafer T, Krummenauer F, Mettelsiefen J, et al. Social, educational, and occupational predictors of total hip replacement outcome. Osteoarthritis Cartilage 2010;18(8):1036. 3. Greene ME, Rolfson O, Nemes S, et al. Education attainment is associated with patient-reported outcomes: findings from the Swedish Hip Arthroplasty Register. Clin Orthop Relat Res 2014;472(6):1868. 4. Desmeules F, Dionne CE, Belzile EL, et al. Determinants of pain, functional limitations and health-related quality of life six months after total knee arthroplasty: results from a prospective cohort study. BMC Sports Sci Med Rehabil 2013;5:2. 5. Dy CJ, Marx RG, Bozic KJ, et al. Risk factors for revision within 10 years of total knee arthroplasty. Clin Orthop Relat Res 2014;472(4):1198. 6. Moller AM, Pedersen T, Villebro N, et al. Effect of smoking on early complications after elective orthopaedic surgery. J Bone Joint Surg Br 2003;85(2):178. 7. Jorgensen CC, Kehlet H. Outcomes in smokers and alcohol users after fast-track hip and knee arthroplasty. Acta Anaesthesiol Scand 2013;57(5):631. 8. Singh JA. Smoking and outcomes after knee and hip arthroplasty: a systematic review. J Rheumatol 2011;38(9):1824. 9. Malinzak RA, Ritter MA. Postoperative wound infection: 35 years of experience. Orthopedics 2006;29(9):797. 10. Sadr Azodi O, Bellocco R, Eriksson K, et al. 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 (10):1316. 11. Lavernia CJ, Villa JM, Contreras JS. Alcohol use in elective total hip arthroplasty: risk or benefit? Clin Orthop Relat Res 2013;471(2):504. 12. Espehaug B, Havelin LI, Engesaeter LB, et al. Patient-related risk factors for early revision of total hip replacements - A population register-based case–control study of 674 revised hips. Acta Orthop Scand 1997;68(3):207. 13. Kremers HM, Visscher SL, Kremers WK, et al. The effect of obesity on direct medical costs in total knee arthroplasty. J Bone Joint Surg Am 2014;96A(9):718. 14. Lewallen LW, Kremers HM, Lahr BD, et al. External validation of the National Healthcare Safety Network risk models for surgical site infections in total hip and knee replacements. Infect Control Hosp Epidemiol 2014;35(11):1323. 15. Dowsey MM, Nikpour M, Choong PF. Outcomes following large joint arthroplasty: does socio-economic status matter? BMC Musculoskelet Disord 2014;15:148. 16. Davis ET, Lingard EA, Schemitsch EH, et al. Effects of socioeconomic status on patients' outcome after total knee arthroplasty. Int J Qual Health Care 2008;20(1):40. 17. Singh JA, Lu X, Rosenthal GE, et al. Racial disparities in knee and hip total joint arthroplasty: an 18-year analysis of national Medicare data. Ann Rheum Dis 2014; 73(12):2107. 18. Fiscella K, Burstin HR, Nerenz DR. Quality measures and sociodemographic risk factors: to adjust or not to adjust. JAMA 2014;312(24):2615. 19. Nagasako EM, Reidhead M, Waterman B, et al. Adding socioeconomic data to hospital readmissions calculations may produce more useful results. Health Aff (Millwood) 2014;33(5):786. 20. Singh JA, Lu X, Ibrahim S, et al. Trends in and disparities for acute myocardial infarction: an analysis of Medicare claims data from 1992 to 2010. BMC Med 2014; 12(1):190. 21. Calvillo-King L, Arnold D, Eubank KJ, et al. Impact of social factors on risk of readmission or mortality in pneumonia and heart failure: systematic review. J Gen Intern Med 2013;28(2):269. 22. Kapadia BH, Issa K, Pivec R, et al. Tobacco use may be associated with increased revision and complication rates following total hip arthroplasty. J Arthroplasty 2014;29(4):777. 23. Kapadia BH, Johnson AJ, Naziri Q, et al. Increased revision rates after total knee arthroplasty in patients who smoke. J Arthroplasty 2012;27(9):1690.
Please cite this article as: Maradit Kremers H, et al, Social and Behavioral Factors in Total Knee and Hip Arthroplasty, J Arthroplasty (2015), http:// dx.doi.org/10.1016/j.arth.2015.04.032
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Social and Behavioral Factors in Total Knee and Hip Arthroplasty Hilal Maradit Kremers, MD, MSc a,b, Walter K. Kremers, PhD a, Daniel J. Berry, MD b, David G. Lewallen, MD b a b
Department of Health Sciences Research Mayo Clinic, Rochester, Minnesota Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota
a r t i c l e
i n f o
Article history: Received 12 February 2015 Accepted 28 April 2015 Available online xxxx Keywords: arthroplasty socioeconomic factors smoking alcohol marital status education
a b s t r a c t Social and behavioral factors are important determinants of health outcomes in a number of medical conditions but their role in joint arthroplasty is poorly understood. In a cohort of 20,124 hip and knee arthroplasty procedures, smoking was associated with a significantly higher risk of surgical site infections (hazard ratio 1.7, 95% CI: 1.1–2.6), whereas alcohol use was associated with a lower risk of reoperations and revisions (hazard ratio 0.7, 95% CI: 0.5–0.8). There was no association between marital status and educational attainment with the risk of complications or reoperations in total hip and knee arthroplasty. © 2015 Elsevier Inc. All rights reserved.
Social and behavioral factors are important determinants of health outcomes in a number of medical conditions but their role in total hip (THA) and knee (TKA) arthroplasty is poorly understood. In studies of patient-reported outcomes, married patients and those with a higher education level have better functional outcomes than patients who are single or with low education levels [1–4]. This has been attributed to better social support and coping skills and improved ability to process and apply medical information. Yet, better patient-reported outcomes may not necessarily translate into fewer complications or fewer revision surgeries. For example, TKA patients from communities with the highest education level in New York and California have a higher risk of revision surgery [5], a finding that has been attributed to higher likelihood of well-educated patients to return and seek follow-up care. Among the behavioral factors, smoking is perhaps the best-studied risk factor in THA and TKA [6–10]. Although the adverse effects of smoking around the time of surgery are well-documented, studies in THA and TKA were mostly small, underpowered and lacked long-term follow-up [8]. Similarly, the effects of alcohol consumption on arthroplasty outcomes are poorly understood [7,11,12]. With this background, our objective was to assess the long-term risk of complications, revisions and mortality associated with patients’ marital status, education level, smoking and alcohol use in TKA and THA.
No author associated with this paper has disclosed any potential or pertinent conflicts which may be perceived to have impending conflict with this work. For full disclosure statements refer to doi: http://dx.doi.org/10.1016/j.arth.2015.04.032. Reprint requests: Hilal Maradit Kremers, MD, MSc, 200 First Street SW, Harwick 6-69, Rochester, MN, 55905.
Material and Methods The study comprised 15,890 adult patients (≥ 18 years) who underwent 20,124 primary and revision TKA and THA procedures at a single tertiary care institution in the United States between 1/1/2002 and 12/31/2009. Revision procedures performed for infected joint arthroplasties were excluded. Information on demographics, surgical characteristics (i.e., surgery type, indications, prior surgeries on the joint, ASA score, procedure duration), body mass index (BMI), diabetes mellitus and arthroplasty outcomes (dates and types of complications within the first year, reoperations, revisions, death) were ascertained through the institutional joint registry, as previously described [13,14]. Briefly, baseline and follow-up data collection is performed by trained registry staff using pre-defined data collection forms and standard operating procedures. All patients are followed up by the surgeon at least twice in the first postsurgical year, in years 2 and 5 and at 5-year intervals thereafter in order to ascertain various arthroplasty outcomes, including details of revision surgeries. If in-person follow-up examination at the clinic is not possible, patients are contacted by letter and/or telephone and asked to complete a standardized data collection form which includes information on complications, reoperations and revisions. The overall clinical follow-up is excellent with more than 65% complete at 30 years. Information on marital status, education, smoking and alcohol use was retrieved from the patient-provided forms stored as part of the patients’ electronic medical records. Marital status was defined based on patients’ responses to their relationship status at the time of surgery (i.e., married, widowed, divorced, single, committed relationship). Education level was categorized under 6 categories based on patients’ report of the highest grade of school that they had completed. Smoking status was classified as current, former or never based on patients’ responses to questions on current and past
http://dx.doi.org/10.1016/j.arth.2015.04.032 0883-5403/© 2015 Elsevier Inc. All rights reserved.
Please cite this article as: Maradit Kremers H, et al, Social and Behavioral Factors in Total Knee and Hip Arthroplasty, J Arthroplasty (2015), http:// dx.doi.org/10.1016/j.arth.2015.04.032
2
H. Maradit Kremers et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx
smoking history. Alcohol use was defined based on patients’ response to 2 questions related to alcohol use: “Have you ever felt the need to cut down on your alcohol consumption?” and “Do relatives/friends worry or complain about your alcohol consumption?” Patient-provided information was missing in roughly 30% of procedures performed during the study time window. Multivariable Cox proportional hazard models were used to estimate hazard ratios (HRs) for each risk factor adjusting for age, gender, BMI, calendar year, surgery type, number of prior surgery on same joint, diabetes status, ASA score and procedure duration. Patients with missing data were treated as a separate category. We examined 5 different outcomes: surgical site infections and overall complications (including implant loosening, instability, dislocation, bone or implant fractures, vascular, neurological, soft tissue, alignment, wound problems, thrombovascular events, patellar complications, osteolysis) within the 12-month window following surgery, reoperations and revisions at any time during follow-up and death. A robust sandwich covariance estimator was used to correct for within-subject correlation for those with multiple surgeries.
Results The study cohort included 10,438 TKA and 9688 THA procedures of which 20% were revision surgeries. Mean age was 66.3 years and 45% were male. At the time of surgery, a majority of patients (53%) reported being married (Table 1). About a third of patients were high school graduate or less and about a quarter had four or more years of college or post-graduate education. At the time of surgery, only 5% were current, 26% were former smokers. Thirteen percent answered yes to one of the two questions related to alcohol use. In multivariate Cox regression models, we observed no relationship between marital status and educational attainment and the risk of surgical site infections, complications, reoperations or revisions (Table 1). Current smoking was associated with a significantly higher risk of surgical site infections (HR: 1.7, 95% CI: 1.1–2.6), but not the overall risk of complications, reoperations or revisions. Alcohol use was associated with a significantly lower risk of reoperations and revision surgeries (HR: 0.7, 95% CI: 0.5–0.8). Despite the lack of association with selected arthroplasty outcomes, marital status and educational
attainment were significant predictors of death, similar to the associations observed in the general population. Discussion We examined the role of selected patient-reported social and behavioral factors on arthroplasty outcomes in a contemporary cohort of patients who underwent THA and TKA surgery at a large tertiary care center in the United States. Our findings indicate that two nonclinical, non-modifiable social factors (education and marital status) are not associated with a higher risk of complications or reoperations. Current smokers have a higher risk of surgical site infections. Collectively, these findings indicate that, apart from efforts to discourage smoking, there is no evidence for implementation of different or intensive post-arthroplasty support strategies for patients who are single or of low education level. The mechanisms through which social and behavioral risk factors have an effect on health outcomes are complex and not always clear. Arthroplasty patients from low socioeconomic groups report worse preoperative pain and function, but seem to benefit equally from surgery [15,16]. Differences in socioeconomic composition, healthcare systems and socioeconomic measures across countries imply that the findings of some excellent studies are not always generalizable to other countries. Within the United States, there is growing recognition of sociodemographic disparities in outcomes of a number of conditions including THA and TKA [17], and such disparities recently triggered discussions on adjustment of quality measures for sociodemographic risk factors [18,19]. Yet, empirical evidence for disparities in clinical outcomes of arthroplasty is limited to race and insurance status [20]. We examined 2 important social factors (marital status and education) which are known to be associated with patient-reported outcomes in arthroplasty [1–4], and certainly influence post-discharge clinical outcomes in other chronic or acute conditions [19,21]. We found no evidence that marital status or education is associated with either a higher rate of complications or revisions in THA and TKA. Lack of associations with arthroplasty outcomes in this study may be in part attributable may be in part attributable to the elective nature of the THA and TKA hospitalizations as compared to acute hospitalizations for pneumonia or heart failure. Although one previous study reported a higher likelihood of revisions in communities with higher education levels [5], findings are not easily comparable because we relied on individual-
Table 1 Risk of Selected Outcomes Associated with Social and Behavioral Risk Factors in a Cohort of 20124 THA and TKA Procedures. Hazard Ratio (95% Confidence Intervals)a
Marital status Married Divorced/widowed Single missing Education 8th grade or less Some high school High school graduate Some college 4-year college graduate Post-graduate missing Smoking Never Former Current missing Alcohol use No Yes missing
N (%)
Surgical Site Infections
Any Complication
Reoperation
Revision
Death
10,584 (53%) 2809 (14%) 756 (4%) 5975 (30%)
1 (ref) 1.1 (0.8–1.5) 1.0 (0.6–1.8) 1.2 (0.5–2.7)
1 (ref) 1.1 (1.0–1.2) 1.0 (0.9–1.2) 1.0 (0.8–1.3)
1 (ref) 1.1 (0.9–1.3) 0.9 (0.7–1.2) 1.1 (0.7–1.6)
1 (ref) 1.0 (0.7–1.2) 0.8 (0.6–1.2) 1.1 (0.7–1.9)
1 (ref) 1.2 (1.1–1.4) 1.6 (1.3–1.9) 2.8 (2.0–3.9)
638 (3%) 670 (3%) 4884 (24%) 3430 (17%) 1919 (10%) 2670 (13%) 5913 (29%)
0.8 (0.4–1.6) 0.9 (0.5–1.8) 1 (ref) 1.0 (0.7–1.4) 1.3 (0.9–2.0) 0.8 (0.5–1.3) 0.9 (0.6–1.4)
1.0 (0.9–1.2) 1.0 (0.8–1.1) 1 (ref) 1.0 (0.8–1.1) 1.0 (0.9–1.1) 1.0 (0.9–1.1) 1.2 (0.9–1.5)
1.1 (0.8–1.4) 1.0 (0.8–1.3) 1 (ref) 0.9 (0.8–1.1) 0.9 (0.8–1.1) 1.0 (0.8–1.1) 1.0 (0.7–1.6)
1.0 (0.7–1.6) 0.9 (0.6–1.4) 1 (ref) 0.9 (0.7–1.1) 1.0 (0.7–1.3) 1.1 (0.9–1.3) 0.8 (0.5–1.6)
1.2 (1.1–1.5) 1.0 (0.8–1.2) 1 (ref) 0.9 (0.8–1.1) 0.8 (0.7–0.9) 0.7 (0.6–0.8) 0.8 (0.6–1.3)
7678 (38%) 5325 (26%) 951 (5%) 6170 (31%)
1 (ref) 1.0 (0.8–1.3) 1.7 (1.1–2.6) 1.5 (0.6–3.7)
1 (ref) 1.0 (0.9–1.1) 1.0 (0.9–1.2) 0.8 (0.6–1.1)
1(ref) 1.0 (0.9–1.1) 1.1 (0.9–1.4) 1.1 (0.7–1.7)
1(ref) 1.1 (0.9–1.3) 1.2 (0.9–1.6) 0.7 (0.3–1.4)
1(ref) 1.2 (1.1–1.3) 2.2 (1.8–2.6) 1.9 (1.3–2.8)
11614 (58%) 2691 (13%) 5819 (29%)
1 (ref) 0.7 (0.5–1.0) 0.7 (0.2–2.2)
1 (ref) 0.9 (0.8–1.0) 1.0 (0.7–1.3)
1 (ref) 0.8 (0.7–0.9) 0.8 (0.4–1.3)
1 (ref) 0.7 (0.5–0.8) 1.5 (0.7–3.3)
1 (ref) 1.0 (0.9–1.2) 0.9 (0.7–1.2)
a Estimates from multivariable Cox regression models adjusting for age, gender, BMI, calendar year, prior surgery, prior TJA, diabetes, ASA score, procedure time, alcohol, smoking, education, marital status.
Please cite this article as: Maradit Kremers H, et al, Social and Behavioral Factors in Total Knee and Hip Arthroplasty, J Arthroplasty (2015), http:// dx.doi.org/10.1016/j.arth.2015.04.032
H. Maradit Kremers et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx
level education status as compared to the community-level measures in the previous study. Our findings with smoking are in line a recent systematic review [8] that reported a higher risk of infection, other complications, and mortality among smokers. Yet, we found no evidence for an association between smoking and the risk of revision surgery. This is in contrast to at least two small studies [22,23] which suggested that smoking may be associated with increased risk of aseptic loosening due to delayed bone healing and bone regeneration. Furthermore, although our measure of alcohol use was rather crude, we observed a significantly lower risk of revisions among patients who were at least moderate drinkers. The reasons for this are unclear, but this was previously suggested in some reports [11,12]. Further studies with more sensitive measures of smoking history and alcohol use are warranted to examine their effects in THA and TKA patients. Due to the retrospective design and reliance on patient-reported data collected for clinical purposes, data on risk factors were missing in about 30% of procedures (i.e., forms were not completed by patients). Age was the main determinant of missingness where a higher percentage of young patients had missing patient-provided forms (i.e., N 50% in patients 40 years and younger versus 20% in patients N 70 years of age). Instead of excluding patients with missing data from the analyses, we instead examined them as a separate category. We found a lack of any association in patients with missing data suggesting that missingness was probably random and not associated with the risk of outcomes. We further examined mortality as a separate outcome to validate the population-level risk factor associations. Our outcome measures were limited to arthroplasty-related clinical outcomes. Education and marital status are only two of many measures of socioeconomic status which may be more directly related to clinical outcomes, such as income, insurance, housing situation, urban–rural location or proximity to hospital. Furthermore, although we failed to identify associations with selected clinical outcomes, these risk factors may still be associated with other arthroplasty outcomes such as the range of motion, patient satisfaction, ability to walk without assistive device, degree of residual pain, or ability to return to full activities, discharge disposition or readmissions. Our measures of smoking status and alcohol use are also not sensitive enough to examine dose response relationships as we had no information on the amount of smoking or alcohol use. There are few objective measures of alcohol use and patients typically under-report their use. The alcohol use questions in this study are vague and likely may have been answered in the negative by some heavy users. Therefore, our findings with alcohol use need to be interpreted with caution. The unique strengths of our study are availability of both short and longterm outcome data available through an institutional joint registry, unique ability to link registry data with medical records and ability to adjust for several clinically important confounders. In conclusion, there is a need to address the social and behavioral determinants of long-term outcomes in THA and TKA. Our findings indicate that these procedures may differ from other conditions and the
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Please cite this article as: Maradit Kremers H, et al, Social and Behavioral Factors in Total Knee and Hip Arthroplasty, J Arthroplasty (2015), http:// dx.doi.org/10.1016/j.arth.2015.04.032
