Introduction: People of color in the United States have an increased risk for delayed surgery, complications, readmissions, and mortality following spine surgery. Social determinants of health represent the complex conditions of an individual’s lived environment, including the social structure and economic systems that affect health. The contribution of the Center for Disease Control’s community-level Social Vulnerability Index (SVI) as a social determinant of racial disparities in the safety of spine surgery is unknown.

Methods: We performed a retrospective analysis of Medicare claims from 2015-2017 to identify racial differences in the rates of mortality, readmission, and complications among patients undergoing spine surgery. We included fee-for-service beneficiaries aged 65 or older with a hospital Diagnosis Related Group (DRG) code for spinal surgery as defined by Medicare, including cohorts labeled as “cervical fusion”, “fusion, except cervical”, “anterior-posterior combined fusion”, “complex fusion”, and “back or neck surgery, except fusion”.  Our primary independent variable was race, which was coded as “black” (Black or African American), “white” (white or Caucasian), and a combined “other” (includes other, Asian, Hispanic Ethnicity, and North American Native).  The SVI reflects community disadvantage at the U.S. Census Tract level in socioeconomic (poverty, work, education, income), household composition and disability, minority and language, and housing and transportation domains.  Logistic regression and propensity-matched analyses adjusted for age, sex, comorbidities, and spine cohort were used to calculate the percentage of disparities between black and white patients explained by SVI.

Results: A total of 209,137 eligible Medicare beneficiaries met inclusion criteria for this analysis. The majority of the population (89.8%) was white, with 5.6% black. Unadjusted rates of surgical safety measures among black and white patients, respectively, were 2.3% and 1.7% for mortality, 17.1% and 14.4% for readmission, 22.3% and 18.6% for complications without associated readmission, and 27.2% and 25.1% for complications with readmission. Logistic regression and propensity-matched analyses without factoring in SVI showed significantly increased rates of mortality, readmission, and complications in black patients compared to white patients. Adding SVI into the models explained 9.4-28.6% of the difference in safety measures between black and white patients, depending on the measure. Most notably, SVI explained 20.0-28.6% of the disparity in mortality rates between black and white patients.

Discussion: Social vulnerability explains up to nearly 30% of the racial health disparities in safety measures between black and white Medicare beneficiaries following spine surgery. This finding is consistent with an Institute of Medicine report that showed socioeconomic status, racism, and culture each explain roughly one-third of disparities encountered in the United States. Focused policies to support vulnerable communities may lead to a meaningful reduction in racial health disparities.

Figure 1: Unadjusted cumulative mortality rate following spine surgery among Medicare beneficiaries, by race.