Agreement between the Sanders Maturity Scale and Pelvic Maturity Indicators in Children with Idiopathic Scoliosis: A Validation Study

Vojtech Capek, Sara Brandt Knutsson, Per Wessberg, Helena Brisby, Olof Westin  

Spine (Phila Pa 1976). 2025 Dec 11. doi: 10.1097/BRS.0000000000005597. Online ahead of print.

ABSTRACT

Study design: Validation study on the agreement between the Sanders Maturity Scale (SMS) and the Pelvic Maturity Indicators (PMI) scale.

Objective: To validate the PMI concept and assess its reliability.

Summary of background data: Reliable assessment of skeletal maturity is essential for the management of adolescent idiopathic scoliosis (AIS). The pelvic maturity indicators system (PMI) was developed to link two most commonly used skeletal maturity scales, the Risser sign (RS) and SMS. This study aimed to validate the PMI using a blinded, multi-rater agreement design.

Methods: Sixty-seven consecutive AIS patients with both hand and pelvic radiographs obtained within a three-month interval were included and evenly distributed across SMS categories. The PMI comprises seven stages observable on pelvic radiographs. Radiographs were anonymized, randomized, and assessed by four raters in one SMS survey and two consecutive PMI surveys. Gold-standard ratings were established for each patient. Agreement between PMI and SMS was analyzed using Spearman’s rank correlation, Cohen’s κ, and Krippendorff’s α to evaluate correlation, pairwise, and multi-rater agreement, respectively.

Results: PMI and SMS demonstrated strong correlation (ρ=0.88; 95% CI, 0.77-0.93) and substantial agreement (κ=0.69; 95% CI, 0.60-0.79). Exact stage concordance was observed in 51% of cases. PMI stages 2, 3, 4, and 7 showed the highest concordance with SMS (100%, 64%, 50%, and 42%, respectively). Inter-rater agreement for SMS and PMI was near perfect (α=0.96; 95% CI, 0.95-0.97) and substantial (α=0.82; 95% CI, 0.78-0.86), respectively.

Conclusions: The PMI is a validated and reliable extension of the Risser sign, demonstrating substantial agreement with SMS. It provides a clinically useful framework linking triradiate cartilage, RS, and SMS grading systems in skeletal maturity assessment.

Level of evidence: II.

Keywords: Sanders maturity scale; agreement; idiopathic scoliosis; inter-rater reliability; intra-rater reliability; maturity assessment; pelvic maturity indicators; scoliosis; skeletal maturity; triradiate cartilage; validation.

https://pubmed.ncbi.nlm.nih.gov/41396364/