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Background and purpose: The study’s purpose was to develop and internally validate a prognostic survival model exploring baseline variables for adolescent idiopathic scoliosis curve progression. Methods: A longitudinal prognostic cohort analysis was performed on trial data (n = 135) including girls and boys, Cobb angle 25–40°, aged 9–17 years, remaining growth > 1 year, and previously untreated. Prognostic outcome was defined as curve progression of Cobb angle of > 6° prior to skeletal maturity. 34 candidate prognostic variables were tested. Time-to-event was measured with 6-month intervals. Cox proportional hazards regression survival model (CoxPH) was used for model development and validation in comparison with machine learning models (66.6/33.3 train/test data set). The models were adjusted for treatment exposure. Results: The final primary prognostic model included 127 patients, predicting progress with acceptable discriminative ability (concordance = 0.79, 95% confidence interval [CI] 0.72–0.86). Significant prognostic risk factors were Risser stage of 0 (HR 4.6, CI 2.1–10.1, P < 0.001), larger major curve Cobb angle (HRstandardized 1.5, CI 1.1–2.0, P = 0.005), and higher score on patient-reported pictorial Spinal Appearance Questionnaire (pSAQ) (HRstandardized 1.4, CI 1.0–1.9, P = 0.04). Treatment exposure, entered as a covariate adjustment, contributed significantly to the final model (HR 3.1, CI 1.5–6.0, P = 0.001). Sensitivity analysis displayed that CoxPH maintained acceptable discriminative ability (AUC 0.79, CI 0.65–0.93) in comparison with machine learning algorithms. Conclusion: The prognostic model (Risser stage, Cobb angle, pSAQ, and menarche) predicted curve progression of > 6° Cobb angle with acceptable discriminative ability. Adding patient report of the pSAQ may be of clinical importance for the prognosis of curve progression.

IMPORTANCE Moderate-grade adolescent idiopathic scoliosis (AIS) may be treated with full-timebracing. For patients who reject full-time bracing, the effects of alternative, conservativeinterventions are unknown. OBJECTIVE To determine whether self-mediated physical activity combined with either nighttimebracing (NB) or scoliosis-specific exercise (SSE) is superior to a control of physical activity alone (PA)in preventing Cobb angle progression in moderate-grade AIS. DESIGN, SETTING, AND PARTICIPANTS The Conservative Treatment for Adolescent IdiopathicScoliosis (CONTRAIS) randomized clinical trial was conducted from January 10, 2013, throughOctober 23, 2018, in 6 public hospitals across Sweden. Male and female children and adolescentsaged 9 to 17 years with an AIS primary curve Cobb angle of 25° to 40°, apex T7 or caudal, and skeletalimmaturity based on estimated remaining growth of at least 1 year were included in the study. Datesof analysis were from October 25, 2021, to January 28, 2023. INTERVENTIONS Interventions included self-mediated physical activity in combination with eitherNB or SSE or PA (control). Patients with treatment failure were given the option to transition to afull-time brace until skeletal maturity. MAIN OUTCOMES AND MEASURES The primary outcome was curve progression of 6° or less(treatment success) or curve progression of more than 6° (treatment failure) seen on 2 consecutiveposteroanterior standing radiographs compared with the inclusion radiograph before skeletalmaturity. A secondary outcome of curve progression was the number of patients undergoing surgeryup until 2 years after the primary outcome. RESULTS The CONTRAIS study included 135 patients (45 in each of the 3 groups) with a mean (SD)age of 12.7 (1.4) years; 111 (82%) were female. Treatment success was seen in 34 of 45 patients (76%)in the NB group and in 24 of 45 patients (53%) in the PA group (odds ratio [OR], 2.7; 95% CI, 1.1-6.6).The number needed to treat to prevent curve progres, Funding: Swedish Research Council [2012-01771]; Stockholm County Council; Swedish Society of Spinal Surgeons; Karolinska Institutet; Crown Princess Lovisas Foundation