The Closing Triradiate Cartilage Sign in Pelvic Radiographs is an Important Marker in Maturity Assessment in Patients With Idiopathic Scoliosis: A Study on Agreement Between the Sanders Maturity Scale and Pelvic Maturity Indicators

Agreement analysis of retrospectively collected data. To perform an agreement analysis between the Sanders maturity scale and pelvic maturity indicators in patients with idiopathic scoliosis. A reliable maturity assessment is mandatory for adolescent idiopathic scoliosis treatment. The two most common skeletal maturity surrogates are the Sanders maturity scale (SMS) and Risser staging (RS). The relationship between these has been scarcely investigated. From a previous brace study, 130 consecutive patients with both pelvic and hand radiographs with a maximum 3-month interval between examinations were selected. The pelvic maturity indicators (PMI) scale combining the Risser sign and triradiate cartilage stage was developed. The PMI consists of six stages (2-7) that were tested against corresponding SMS stages. An agreement analysis between the PMI based on the pelvic radiograph and the SMS of the hand image was conducted. The Spearman rank correlation and Cohen κ with Gwet's AC1 coefficient were the measures of correlation and agreement, respectively. The PMI and SMS showed a strong correlation (Spearman ρ= 0.79; 95% CI: 0.72, 0.85) and substantial agreement (Gwet's AC1 = 0.76; 95% CI: 0.70, 0.82). The highest accuracy in matching PMI to SMS was observed for PMI 2, 3, and 7, with 83.3%, 80.0%, and 88.9% correctly matched SMS stage to corresponding PMI stage. The regression model accurately predicted five of six SMS stages from pelvic radiographs. The triradiate cartilage staging facilitated the maturity assessment of the pelvic radiographs and showed a strong correlation to and substantial agreement with the SMS. The most important stages for AIS development, SMS 2, 3, and 7, showed the best matching accuracy to PMI. The pelvic image of PMI 3 with closing triradiate cartilage corresponds to SMS stage 3. Level III.