Evidence-Based Thresholds for the Volume-Value Relationship in Adolescent Idiopathic Scoliosis: Outcomes and Economies of Scale.

OBJECTIVES: Increased surgeon and hospital volume has been associated with improved patient outcomes and cost effectiveness for adolescent idiopathic scoliosis (AIS). However, no evidence-based thresholds that clarify the volume at which these strata occur exist. The objective of this study was to establish statistically meaningful thresholds that define high-volume surgeons and hospitals performing spinal fusion for AIS from those that are low volume with respect to length of stay (LOS) and cost.

METHODS: Using 3,224 patients undergoing spinal fusion for AIS from an administrative database, we created and applied four models using stratum-specific likelihood ratio (SSLR) analysis of a receiver operating characteristic (ROC) curve. We generated four sets of thresholds predictive of adverse outcomes, namely, increased cost and LOS, for both surgeon and hospital volume.

RESULTS: For both LOS and cost, surgeon volume produced the same strata with low volume identified as 0-5 annual surgeries and high as greater than 5. LOS and cost decreased significantly (p < .05) between volume strata. For hospital volume in terms of LOS, low volume was identified as 0-10 annual surgeries and high as greater than 10; in terms of cost, low volume was identified as 0-15 annual surgeries and high as greater than 15. LOS decreased significantly (p < .05) and cost was $1,500 less but not statistically significant between volume strata for hospital volume.

CONCLUSIONS: Our study of risk-based volume stratification established a direct volume-value relationship for surgeons and hospitals performing fusion for AIS. A meaningful threshold for low- and high-volume surgeons was established at 5 annual surgeries, but no consensus or clinically meaningful conclusion was reached for hospitals, although the threshold approached 10-15 annual surgeries. This analysis should aid patients, surgeons, and administration reach value-based decisions in the optimal delivery of pediatric spinal fusion for AIS.