Disparities in TKA Outcomes: Census Tract Data Show Interactions Between Race and Poverty.
BACKGROUND
Race is an important predictor of TKA outcomes in the United States; however, analyses of race can be confounded by socioeconomic factors, which can result in difficulty determining the root cause of disparate outcomes after TKA.


OBJECTIVE
We asked: (1) Are race and socioeconomic factors at the individual level associated with patient-reported pain and function 2 years after TKA? (2) What is the interaction between race and community poverty and patient-reported pain and function 2 years after TKA?


METHODS
We identified all patients undergoing TKA enrolled in a hospital-based registry between 2007 and 2011 who provided 2-year outcomes and lived in New York, Connecticut, or New Jersey. Of patients approached to participate in the registry, more than 82% consented and provided baseline data, and of these patients, 72% provided 2-year data. Proportions of patients with complete followup at 2 years were lower among blacks (57%) than whites (74%), among patients with Medicaid insurance (51%) compared with patients without Medicaid insurance (72%), and among patients without a college education (67%) compared with those with a college education (71%). Our final study cohort consisted of 4035 patients, 3841 (95%) of whom were white and 194 (5%) of whom were black. Using geocoding, we linked individual-level registry data to US census tracts data through patient addresses. We constructed a multivariate linear mixed-effect model in multilevel frameworks to assess the interaction between race and census tract poverty on WOMAC pain and function scores 2 years after TKA. We defined a clinically important effect as 10 points on the WOMAC (which is scaled from 1 to 100 points, with higher scores being better).


RESULTS
Race, education, patient expectations, and baseline WOMAC scores are all associated with 2-year WOMAC pain and function; however, the effect sizes were small, and below the threshold of clinical importance. Whites and blacks from census tracts with less than 10% poverty have similar levels of pain and function 2 years after TKA (WOMAC pain, 1.01 ± 1.59 points lower for blacks than for whites, p = 0.53; WOMAC function, 2.32 ± 1.56 lower for blacks than for whites, p = 0.14). WOMAC pain and function scores 2 years after TKA worsen with increasing levels of community poverty, but do so to a greater extent among blacks than whites. Disparities in pain and function between blacks and whites are evident only in the poorest communities; decreasing in a linear fashion as poverty increases. In census tracts with greater than 40% poverty, blacks score 6 ± 3 points lower (worse) than whites for WOMAC pain (p = 0.03) and 7 ± 3 points lower than whites for WOMAC function (p = 0.01).


CONCLUSIONS
Blacks and whites living in communities with little poverty have similar patient-reported TKA outcomes, whereas in communities with high levels of poverty, there are important racial disparities. Efforts to improve TKA outcomes among blacks will need to address individual- and community-level socioeconomic factors.


METHODS
Level III, therapeutic study.
Department of Medicine, Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA. goodmans@hss.edu.
Susan M
SM
Goodman
Department of Medicine, Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA.
Lisa A
LA
Mandl
Department of Orthopaedics, Hospital for Special Surgery, New York, NY, USA.
Michael L
ML
Parks
Department of Biostatistics, Hospital for Special Surgery, New York, NY, USA.
Meng
M
Zhang
Department of Research, Hospital for Special Surgery, New York, NY, USA.
Kelly R
KR
McHugh
Department of Biostatistics, Hospital for Special Surgery, New York, NY, USA.
Yuo-Yu
YY
Lee
Department of Biostatistics, Hospital for Special Surgery, New York, NY, USA.
Joseph T
JT
Nguyen
Department of Medicine, Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA.
Linda A
LA
Russell
Department of Research, Hospital for Special Surgery, New York, NY, USA.
Margaret H
MH
Bogardus
Department of Orthopaedics, Hospital for Special Surgery, New York, NY, USA.
Mark P
MP
Figgie
Department of Medicine, Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA.
Anne R
AR
Bass
D001741:Black or African American; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000191:economics; D019352:Censuses; D016009:Chi-Square Distribution; D015986:Confounding Factors, Epidemiologic; D005260:Female; D054625:Healthcare Disparities / Q000191:economics / Q000208:ethnology; D006621:Hip Joint / Q000503:physiopathology / Q000601:surgery*; D006630:Hispanic or Latino; D006801:Humans; D007592:Joint Diseases / Q000191:economics / Q000208:ethnology / Q000503:physiopathology / Q000601:surgery*; D016014:Linear Models; D008297:Male; D008484:Medicaid / Q000191:economics; D008875:Middle Aged; D015999:Multivariate Analysis; D010147:Pain Measurement; D010149:Postoperative Pain / Q000191:economics / Q000208:ethnology; D000071066:Patient Reported Outcome Measures; D011203:Poverty / Q000191:economics / Q000208:ethnology; D020127:Recovery of Function; D012042:Registries; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology; D044465:White People