Delay to Surgery Greater Than 6 Months Leads to Substantial Deformity Progression and Increased Intervention in Immature Adolescent Idiopathic Scoliosis (AIS) Patients: A Retrospective Cohort Study

Design: A retrospective, multi-institution series of adolescent idiopathic scoliosis (AIS) patients whose date of surgery exceeded six months from date of surgical recommendation were identified. A case-matched comparison of surgical outcomes of skeletally immature patients who delayed surgery versus a cohort of nondelayed patients. Objectives: We sought to identify 1) whether patients at risk for significant curve progression when delaying surgery could be identified with available clinical and radiographic data and 2) whether patients who delay surgery have longer fusions/more complex procedures. Background: Multiple factors can lead to a delay in treatment of AIS once surgical treatment is recommended, and larger Cobb magnitudes have been associated with a more complex surgery. Methods: 143 AIS patients who delayed surgery had deformity progression (major Cobb angle change over time) analyzed by Risser grade, triradiate cartilage (TRC) status, and menarche status. Comparison of at-risk patients with regard to surgical outcomes to a cohort of matched patients who had not delayed surgery. Results: Risser 0 patients (n = 34) had a greater major Cobb progression than Risser 1–5 patients (n = 109): mean 1.6°/mo versus 0.4°/mo, p < .001. Twenty-eight premenarchal patients had significantly greater increases in Cobb angle measures than their postmenarchal counterparts (n = 86) (13.2° vs. 4.3°, p < .001). An open TRC also conferred increasing rate of progression. Radiographic variables of stable vertebra and last vertebra touched by central sacral vertical line were more likely to change in immature patients, but we did not demonstrate longer fusions or higher estimated blood loss as a result when compared to nondelayed, age-matched peers. Conclusion: AIS patients who are premenarchal, TRC open, or Risser 0 who delay surgery greater than 6 months risk clinically significant Cobb angle progression, which is statistically greater than their more mature peers. Clinical ramifications of this remain unclear. Skeletally mature patients do not progress rapidly, allowing elective timing of surgical intervention. Level of Evidence: Level III.