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

STUDY DESIGN: Prospective study. OBJECTIVE: To investigate the difference in major curve Cobb angle and alignment between directed and nondirected positioning for adolescent idiopathic scoliosis (AIS) and to evaluate implications on treatment decision-making. SUMMARY OF BACKGROUND DATA: 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 radiologic parameters and the impact of posture on management decisions remains unknown. PATIENTS AND METHODS: Patients with adolescent idiopathic scoliosis presenting for an initial consultation at a tertiary scoliosis clinic were recruited. They were asked to stand in two positions: passive, nondirected position; and directed position by the radiographer. Radiologic assessment included major and minor Cobb angle, coronal balance, spinopelvic parameters, sagittal balance, and alignment. Cobb angle difference >5° between directed and nondirected positioning was considered clinically impactful. Patients with or without such differences were compared. Overestimation or underestimation of the major curve (at 25° or 40°) by nondirected positioning were examined due to its relevance to bracing and surgical indications. RESULTS: This study included 198 patients, with 22.2% experiencing Cobb angle difference (>5°) between positioning. The major curve Cobb angle was smaller in nondirected than directed positioning (median difference: −6.0°, upper and lower quartile: −7.8, 5.8), especially for curves ≥30°. Patients with a Cobb angle difference had changes in shoulder balance (P=0.007) when assuming a directed position. Nondirected positioning had 14.3% of major Cobb 25° underestimated and 8.8% overestimated, whereas 11.1% of curves >40° were underestimated. CONCLUSION: Strict adherence to a standardized radiographic protocol is mandatory for reproducing spine radiographs reliable for curve assessment, as a nondirected position demonstrates smaller Cobb angles. Postural variation may lead to overestimation, or underestimation, of the curve size which is relevant to both bracing and surgical decision-making. LEVEL OF EVIDENCE: Level—II.