A Comparative Study of Protocols for Spinal Casting in Severe Early-Onset Scoliosis: A Four-Year Progression-Free Survival Analysis

Despite spinal casting being widely accepted as a conservative management strategy to control severe early-onset scoliosis (EOS) and delay surgical intervention, there is no consensus on the most appropriate protocol to optimize outcomes. At our institution an intermittent cast protocol was used prior to November 2018, with 2-3 casts applied over 6 months, followed by bracing and consideration of a repeat cast if progression was later noted. A continuous cast protocol was introduced after November 2018 with casts worn 12-16 weeks, often for 2-3 years. The objective of this study was to compare the outcomes of intermittent versus continuous spinal casting protocols, focusing on progression-free survival at 4-years. This was a retrospective review of prospectively collected data of all 43 EOS patients managed with spinal casting, at a single institution that had at least 2 cast applications (intermittent) or over 12 months of casting (continuous), initiated between November 2002-April 2022. The Kaplan-Meier method estimated the probability of progression-free survival at 4 years, defined as the time to curve progression beyond index or definitive surgical decision, whichever occurred first. A Cox Proportional Hazards model considered the association between survival and cast protocol, sex, etiology, age at first cast, pre-cast Cobb angle, and percent correction achieved in first cast. The hazard ratio (HR) of each variable was calculated. Comparative analyses considered change in Cobb angle over time, including correction in first- versus most recent cast. Thirty patients underwent intermittent casting (24 female, 14 idiopathic), and 13 continuous casting (7 female, 5 idiopathic). At baseline both groups were similar in sex (p=0.17), etiology (p=0.87), and Cobb angle (63.5° vs 69.1°, p=0.26) but differed on age of cast initiation (3.89 years vs 2.7 years, p Non-idiopathic etiology and curve stiffness decrease the probability of 4-year progression-free survival for severe EOS patients treated with spinal casting. A continuous cast protocol allows for on-going improvement of in-cast Cobb angle however does not demonstrate a survival advantage in the short term. Both protocols effectively delay surgery in severe EOS patients.