The Cost of Social Disadvantage: Increased Postoperative Risk in TKA Patients

Introduction

Social Determinants of Health (SDOH) contribute to disparities in healthcare delivery and patient outcomes. Previous studies have demonstrated that factors related to social vulnerability, including socioeconomic status, education, and access to care significantly impact outcomes following orthopedic surgical procedures. The CDC's 2018 Social Vulnerability Index (SVI), developed using 16 U.S. Census variables, serves as a tool to approximate social disparity. While prior studies have associated a high SVI score with poor postoperative outcomes in total joint arthroplasty, regional differences in healthcare infrastructure and population demographics are hypothesized to influence this relationship. Houston, Texas serves as a valuable model to evaluate this relationship due to the diverse patient population and high surgical caseload. This study aims to investigate the relationship between patient SVI score and postoperative outcomes following TKA at a large academic medical center in Houston, Texas.

Methods

This retrospective cohort study analyzed 9,191 patients who underwent primary TKA between January 1, 2013 and December 31, 2023 at a private medical center in Houston, Texas. Patients who underwent primary TKA during this period were identified using International Classification of Diseases (ICD) codes. Those who underwent revision TKA or unicondylar knee arthroplasty were excluded. Postoperative complications evaluated include prolonged length of stay (≥5 days post-op), incidence of 30-day infection and 90-day infection, as well as 90-day incidence of sepsis, readmission, pulmonary embolism (PE), deep vein thrombosis (DVT), myocardial infarction (MI), and cerebrovascular accident (CVA). Given the baseline rarity of complications following primary TKA, Firth Logistic regression was used to evaluate associations between SVI scores and complications. Odds ratios and 95% confidence intervals were reported for significant associations. A p-value of <0.05 was considered statistically significant.

Results

After adjusting for confounders, each 1% increase in SVI score was associated with a 0.9% increase in the odds of PE within 90 days (OR = 1.009, 95% CI = 1.002-1.016, p-value = 0.013) and a 0.9% increase in the odds of infection within 30 days following surgery (OR = 1.009, 95% CI = 1.0002-1.017, p-value=0.044). No significant associations were identified for sepsis, postoperative readmission, DVT, MI, CVA, 90-day infection, or prolonged length of stay.

Conclusion

Higher Social Vulnerability Index scores are associated with increased risk of postoperative pulmonary embolism (within 90 days)and new infection (within 30 days) following TKA. The elevated risk of PE in socially vulnerable patients may warrant closer perioperative monitoring and consideration of more aggressive anticoagulant prophylaxis. Higher infection rates may be attributed to medication access, nutrition, health literacy, housing conditions, language barriers, or insurance status, among other possibilities. Awareness of these associations can guide orthopedic surgeons in preoperative counseling, postoperative management, wound care, and extended thromboprophylaxis strategies to mitigate risks in vulnerable patient populations. Although SVI is a useful indicator of social vulnerability, it primarily reflects the neighborhood and built environment component of SDOH. Further research is needed to explore how other SDOH components contribute to postoperative complications.