177. The influence of hospital type, insurance type and patient income on 30-day complication and readmission rates following lumbar spine fusion

Abstract

BACKGROUND CONTEXT Several studies have shown that factors such as insurance type and patient income are associated with different readmission rates following certain orthopaedic procedures. PURPOSE The present study evaluates 30-day complication and readmission rates as a function of hospital type, insurance type, and patient median income in patients undergoing lumbar spine fusion. STUDY DESIGN/SETTING Retrospective cohort analysis PATIENT SAMPLE Using the National Readmissions Database (NRD), we identified patients who underwent a primary lumbar spine fusion from 2010-2016. OUTCOME MEASURES Primary outcome measures were 30-day readmission and complication rates. Complications of interest were infection, wound injury, hematoma, neurological injury, thromboembolic event, and hardware failure. METHODS International Classification of Diseases, Ninth Revision (ICD-9) and Tenth Revision (ICD-10) codes were used to identify 596,568 patients who underwent a primary lumbar spine fusion from 2010-2016. Three separate analyses were performed using hospital type, insurance type, and patient income quartile as independent variables. Hospital type included the following groups: metropolitan non-teaching (n=212,131), metropolitan teaching (n=364,752), and rural (n=19,685). Insurance type was divided into 4 groups: Medicare (n=213,534), Medicaid (n=78,520), private insurance (n=196,648), and out-of-pocket payers (n=45,025). Income quartiles included Quartiles 1 (n=112,083), 2 (n=145,755), 3 (n=156,276), and 4 (n=147,289), with Quartile 1 corresponding to the poorest populations and Quartile 4 to the wealthiest populations. Nonparametric Kruskal-Wallis testing, followed by Dunn's pairwise comparisons were used to analyze differences in 30-day complication and readmission rates between cohorts. Statistical tests were two-sided with significance level set at α = 0.05. RESULTS Thirty-day readmission was significantly higher in metropolitan teaching hospitals compared to metropolitan non-teaching and rural hospitals (p < 0.05). Metropolitan teaching hospitals had significantly higher rates of infection (p < 0.001), wound injury (p < 0.001), hematoma (p=0.018) and hardware failure (p < 0.002) compared to metropolitan nonteaching hospitals. Privately insured patients were significantly less likely to be readmitted at 30 days than Medicare or Medicaid beneficiaries (p < 0.01). Privately insured patients also experienced significantly lower rates of hematoma formation than Medicare patients and out-of-pocket payers (p < 0.01), wound injury compared to Medicaid patients and out-of-pocket payers (p < 0.005), and infection compared to all other groups (p < 0.001). Patients in Quartile 4 had significantly greater rates of hematoma formation than those in Quartiles 1 and 2 (p < 0.02) and were more likely to experience a thromboembolic event compared to all other groups (p < 0.002). CONCLUSIONS Patients undergoing lumbar spine fusion at metropolitan nonteaching hospitals and paying with private insurance had significantly lower 30-day readmission rates than their counterparts. Complications within 30 days following lumbar spine fusion were significantly higher in patients treated at metropolitan teaching hospitals and in Medicare and Medicaid beneficiaries. Aside from a few exceptions, patient income was generally not associated with differential complication rates. Further understanding of how various hospital characteristics and sociodemographic factors may impact patient outcomes is essential in mitigating drivers of inequitable outcomes in patients undergoing lumbar spine fusion. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs. Several studies have shown that factors such as insurance type and patient income are associated with different readmission rates following certain orthopaedic procedures. The present study evaluates 30-day complication and readmission rates as a function of hospital type, insurance type, and patient median income in patients undergoing lumbar spine fusion. Retrospective cohort analysis Using the National Readmissions Database (NRD), we identified patients who underwent a primary lumbar spine fusion from 2010-2016. Primary outcome measures were 30-day readmission and complication rates. Complications of interest were infection, wound injury, hematoma, neurological injury, thromboembolic event, and hardware failure. International Classification of Diseases, Ninth Revision (ICD-9) and Tenth Revision (ICD-10) codes were used to identify 596,568 patients who underwent a primary lumbar spine fusion from 2010-2016. Three separate analyses were performed using hospital type, insurance type, and patient income quartile as independent variables. Hospital type included the following groups: metropolitan non-teaching (n=212,131), metropolitan teaching (n=364,752), and rural (n=19,685). Insurance type was divided into 4 groups: Medicare (n=213,534), Medicaid (n=78,520), private insurance (n=196,648), and out-of-pocket payers (n=45,025). Income quartiles included Quartiles 1 (n=112,083), 2 (n=145,755), 3 (n=156,276), and 4 (n=147,289), with Quartile 1 corresponding to the poorest populations and Quartile 4 to the wealthiest populations. Nonparametric Kruskal-Wallis testing, followed by Dunn's pairwise comparisons were used to analyze differences in 30-day complication and readmission rates between cohorts. Statistical tests were two-sided with significance level set at α = 0.05. Thirty-day readmission was significantly higher in metropolitan teaching hospitals compared to metropolitan non-teaching and rural hospitals (p < 0.05). Metropolitan teaching hospitals had significantly higher rates of infection (p < 0.001), wound injury (p < 0.001), hematoma (p=0.018) and hardware failure (p < 0.002) compared to metropolitan nonteaching hospitals. Privately insured patients were significantly less likely to be readmitted at 30 days than Medicare or Medicaid beneficiaries (p < 0.01). Privately insured patients also experienced significantly lower rates of hematoma formation than Medicare patients and out-of-pocket payers (p < 0.01), wound injury compared to Medicaid patients and out-of-pocket payers (p < 0.005), and infection compared to all other groups (p < 0.001). Patients in Quartile 4 had significantly greater rates of hematoma formation than those in Quartiles 1 and 2 (p < 0.02) and were more likely to experience a thromboembolic event compared to all other groups (p < 0.002). Patients undergoing lumbar spine fusion at metropolitan nonteaching hospitals and paying with private insurance had significantly lower 30-day readmission rates than their counterparts. Complications within 30 days following lumbar spine fusion were significantly higher in patients treated at metropolitan teaching hospitals and in Medicare and Medicaid beneficiaries. Aside from a few exceptions, patient income was generally not associated with differential complication rates. Further understanding of how various hospital characteristics and sociodemographic factors may impact patient outcomes is essential in mitigating drivers of inequitable outcomes in patients undergoing lumbar spine fusion.