A comparative study of strategies for spinal casting in early onset scoliosis : five-year progression-free survival analysis.

Aims: Spinal casting is accepted as a surgical delay strategy in the management of early onset scoliosis (EOS). There is no consensus on protocol to optimize outcomes. This study compares the five-year outcomes of intermittent casting (IC) with continuous casting (CC) strategies, focusing on deformity control. Methods: This was a progression-free survival analysis informed by retrospective chart review of all EOS patients who had spinal casting between January 2002 and August 2025. IC was defined as two to three casts applied over six months, followed by bracing and single repeat casts if progression was noted. CC was defined as the repeat application of casts every 12 to 16 weeks, over a period > one year. Patients with < 12-month follow-up or with congenital aetiology were excluded. The primary outcome was curve progression > 5° or transition to surgery. Kaplan-Meier analysis with log-rank test compared the efficacy of each strategy to halt curve progression or delay surgery. Cox proportional hazards model was used to estimate the adjusted hazard ratio (aHR) between strategies. In-cast correction and complications related to casting were recorded. Results: Overall, 59% (n = 30) underwent IC and 41% (n = 21) CC. Groups were similar at baseline in sex, age, aetiology, and index curve magnitude (mean 64° (SD 15°)). The five-year progression-free survival rate was 47% (95% CI 33.7 to 66.0), which did not differ by casting strategy (p = 0.095). In-cast correction was stable with CC, whereas less correction was achieved over time with IC (p = 0.004). The adjusted risk of progression decreased with greater correction in first cast (aHR 0.48, 95% CI 0.28 to 0.83, p = 0.009) and increased with larger index curve magnitudes (aHR 3.01, 95% CI 1.48 to 6.12, p = 0.002). Each group had one complication. Conclusion: There is not a distinct advantage with a CC strategy over an IC strategy with both offering deformity control and meaningful delays in surgery for EOS patients. The long-term implications of ongoing in-cast correction seen with CC are yet to be determined.