Impact of Readmissions in Episodic Care of Adult Spinal Deformity Event-Based Cost Analysis of 695 Consecutive Cases

Background: Readmissions following adult spinal deformity surgical procedures frequently occur, placing a substantial burden on patients and providers. Existing literature on readmission costs, including reason-specific readmission costs, is limited. The purposes of this study were to determine the most expensive reasons for readmission, to assess the impact of reasons and timing on readmission costs, and to estimate the drivers of total costs associated with adult spinal deformity surgical procedures. Methods: We performed a retrospective review of 695 patients with adult spinal deformity (>= 18 years of age) who underwent a corrective spine surgical procedure at a single center from 2005 to 2013. Demographic, surgical, and direct cost data expressed in 2010 dollars for the entire inpatient episode of care were obtained from the hospital administrative database. A multivariable linear regression model with a gamma distribution and log-link function was used to estimate the impact of reasons and timing on readmission costs and to identify the primary drivers of long-term costs. Results: The mean age (and standard deviation) of the patients was 50.6 +/- 15.8 years, 589 patients (85%) were women, and 637 patients (92%) were Caucasian. The observed readmission rates were 24% overall (costing $10.1 million), 8.8% for 30 days (costing $3.2 million), and 11.7% for 90 days (costing $4.6 million). The most expensive readmissions and their mean readmission cost were pseudarthrosis ($92,755), infection ($75,172), and proximal junctional kyphosis ($66,713), after adjusting for patient and surgical factors. The mean readmission cost after 2 years was $86,081. Older age (p = 0.001), >= 8 levels fused (p = 0.01), and length of index stay at the hospital (p < 0.0001) were independently associated with higher total cost. Surgical procedures in patients with a thoracic-only curve (p = 0.004) or a double curve (p = 0.05) and a surgical approach that was anterior-only (p < 0.0001) or posterior-only (p = 0.01) were independently associated with lower total costs. Conclusions: Compared with readmission cost due to medical reasons, readmission due to pseudarthrosis increases mean readmission cost by 105%, readmission due to infection increases mean readmission cost by 72%, and readmission due to proximal junctional kyphosis increases mean readmission cost by 63%. Together, these 3 reasons accounted for 73% of readmission costs. This study identifies potential areas for cost reduction and opportunities for reducing readmission rates.