A noninvasive spinal device for measuring adolescent idiopathic scoliosis: validity, reliability, and factors influencing measurement difference

BackgroundAdolescent idiopathic scoliosis (AIS) is a common deformity, requiring regular screening and monitoring. While radiological measurements are considered the gold standard, X-ray exposure poses significant risks. A noninvasive spinal device offers a radiation-free alternative for measuring spinal curvature. This study evaluates the validity and reliability of its measurements and explores factors associated with measurement discrepancy.MethodsThis study involved AIS patients in an outpatient setting from June to August 2023. Participants underwent device measurements to assess the scoliosis angle (SA) in the frontal plane, which were evaluated by two orthopedists and compared to radiological measurements (Cobb angle) from EOS images.ResultsA total of 112 patients were included in the study. The Cobb angle measured on EOS images was 30.3 degrees +/- 12.4 degrees. The SA measurements by observer 1, observer 2, and their average were 25.5 degrees +/- 10.9 degrees, 25.4 degrees +/- 10.3 degrees, and 25.4 degrees +/- 9.9 degrees, respectively. The reliability analysis showed good agreement between observers (ICC = 0.77) and within observers (ICCs of 0.81 and 0.86). The validity analysis showed a very strong correlation between the SA and Cobb angle (r = 0.76). Logistic regression analysis indicated that high BMI, great scoliosis magnitude, and large maximal vertebral rotation (MVR) were associated with measurement discrepancy. Multivariate linear regression formula was: Cobb angle = 0.83xSA + 0.55xTRA + 0.21xBMI.ConclusionThis device measurement demonstrated good reliability and validity compared with radiological measurement, highlighting its safety and feasibility for screening and monitoring AIS progression. However, high BMI, great scoliosis magnitude, and large MVR were associated with measurement inaccuracy.