Algorithm for Schroth-Curve-Type Classification of Adolescent Idiopathic Scoliosis: An Intra- and Inter-Rater Reliability Study †

Schroth exercises for scoliosis are prescribed based on curve types. This study aimed to determine the reliability of an algorithm for classifying Schroth curve types. Forty-four consecutive volunteers with adolescent idiopathic scoliosis, 10 to 18 years old, with curves 10° to 50°, were recruited from a scoliosis clinic. Their standing posture and Adam’s bending test were videotaped. Ten consecutive Schroth therapist volunteers from an international registry independently classified the curve types using the proposed classification algorithm. Videos were rated twice at least seven days apart. Reliability was calculated using the Gwet’s AC1 agreement coefficient for all the raters and for subgroups reporting full understanding (well-trained) and with prior algorithm experience. The intra-rater and weighted agreement coefficients for all the raters were 0.64 (95% CI: 0.53–0.73) and 0.75 (0.63–0.84), respectively. For the well-trained raters, they were 0.70 (0.60–0.78) and 0.82 (0.73–0.88), respectively; for the experienced raters, they were 0.81 (0.77–0.85) and 0.89 (0.80–0.94), respectively. The inter-rater versus weighted agreement coefficients for all the raters were 0.43 (0.28–0.58) versus 0.48 (0.29–0.67). For the well-trained raters, they were 0.50 (0.38–0.61) versus 0.61 (0.49–0.72), and for the experienced raters, they were 0.67 (0.50–0.85) versus 0.79 (0.64–0.94). Full understanding and experience led to higher reliability. Use of the algorithm can help standardize Schroth exercise treatment.