European Spine Journal - 2026-07-09 - Journal Article
Determining the minimal clinically important difference of angle of trunk rotation for monitoring conservatively treated adolescent idiopathic scoliosis.
Kuru Çolak T, Akçay Genal B, Çolak İ
Topics
Key Takeaway
In conservatively treated AIS, ΔATR ≤ -1.5° identifies radiographic improvement and ΔATR ≥ +0.5° identifies worsening (AUC ~0.78 for both), with brace-plus-exercise patients requiring a larger improvement threshold (-4.5°) than exercise-only patients (-1.5°).
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Summary
This study sought to define treatment-specific MCID values for ATR change in AIS patients managed conservatively, using 6-month Cobb angle change (≥5° improvement or worsening) as the anchor. ROC analysis in 316 patients yielded overall ΔATR cut-offs of ≤-1.5° for improvement and ≥+0.5° for worsening (AUC 0.778 and 0.777, respectively). Subgroup analysis revealed divergent thresholds by treatment modality, with the brace-plus-exercise group requiring a ΔATR of ≤-4.5° to signal radiographic improvement versus ≤-1.5° in the exercise-only group.
Key Limitation
The 6-month follow-up window is too short to capture progression patterns across skeletal maturity, and the MCID anchors are radiographic rather than patient-reported, which may not reflect clinically meaningful functional change.
Original Abstract
PURPOSE
The angle of trunk rotation (ATR) is widely used in the clinical follow-up of adolescent idiopathic scoliosis (AIS); however, the minimal clinically important difference (MCID) has not been clearly defined. This study aimed to determine treatment-specific MCID values for ATR in conservatively treated AIS patients.
METHODS
This retrospective cohort study included 316 AIS patients treated with brace plus exercise or exercise alone. Radiographic outcomes at 6 months were classified as improvement (ΔCobb ≤ - 5°), stabilization (- 5° < ΔCobb < + 5°), or worsening (ΔCobb ≥ + 5°). Receiver operating characteristic (ROC) analyses were performed to determine optimal ΔATR cut-off values for clinically meaningful improvement and worsening in the overall cohort and separately by treatment group.
RESULTS
In the overall cohort, ΔATR showed good discriminative ability for improvement (AUC = 0.778) and worsening (AUC = 0.777). The optimal cut-offs were ΔATR ≤ - 1.5° for improvement and ΔATR ≥ + 0.5° for worsening. In subgroup analyses, the improvement threshold was ΔATR ≤ - 1.5° in the exercise-only group and ≤ - 4.5° in the brace-plus-exercise group. For radiographic worsening, the optimal thresholds were ΔATR ≥ + 0.5° in the exercise-only group and ≥ - 2.5° in the brace-plus-exercise group.
CONCLUSIONS
Treatment-specific ΔATR thresholds provide clinically meaningful benchmarks for monitoring both improvement and worsening, supporting the use of ATR as a practical radiation-free follow-up parameter in AIS management.