Directed Versus non-directed Standing Postures in Adolescent Idiopathic Scoliosis: Its Impact on Curve Magnitude, Alignment and Clinical Decision Making.

Prospective study.To investigate the difference in major curve Cobb angle and alignment between directed and non-directed positioning for adolescent idiopathic scoliosis (AIS) and to evaluate implications on treatment decision-making.Proper positioning of patients with spinal deformities is important for assessing usual functional posture in standing, so management strategies can be customized accordingly. Whether postural variability affects coronal and sagittal radiological parameters and the impact of posture on management decisions remain unknown.Patients with AIS presenting for initial consultation at the tertiary scoliosis clinic were recruited. They were asked to stand in two positions: passive, non-directed position; and directed position by the radiographer. Radiological assessment included major and minor Cobb angle, coronal balance, spinopelvic parameters, sagittal balance and alignment. Cobb angle difference >5⁰ between directed and non-directed positioning was considered clinically impactful. Patients with or without such difference were compared. Over- or under-estimation of the major curve (at 25⁰ or 40⁰) by non-directed positioning were examined due to relevance to bracing and surgical indications.This study included 198 patients, with 22.2% experiencing Cobb angle difference (>5⁰) between positioning. The major curve Cobb angle was smaller in non-directed than directed positioning (median difference: -6.0⁰, upper and lower quartile: -7.8, 5.8), especially for curves ≥30⁰. Patients with a Cobb angle difference had changes in shoulder balance (P=0.007) when assuming a directed position. Non-directed positioning had 14.3% of major Cobb 25⁰ underestimated and 8.8% overestimated, whereas 11.1% of curves >40⁰ were underestimated.Strict adherence to a standardized radiographic protocol is mandatory for reproducing spine radiographs reliable for curve assessment, as a non-directed position demonstrates smaller Cobb angles. Postural variation may lead to over-, or under-estimation, of the curve size relevant for both bracing and surgical decision-making.II.