Preliminary validation of a portable, radiation-free, surface-based system (OmÖS) for sagittal spinal curvature measurement.

Abstract

Radiographic assessment remains the reference standard for measuring sagittal spinal curvatures; however, repeated exposure to ionizing radiation limits its suitability for screening and longitudinal follow-up. This has motivated the development of reliable, radiation-free measurement technologies capable of providing clinically meaningful curvature estimates. This study presents the preliminary validation of a portable, radiation-free, surface-based measurement system (OmÖS) designed for sagittal plane spinal curvature measurement. Thoracic and lumbar curvature angles were measured in 16 volunteers using both lateral spinal radiographs (radiographic Cobb method, RaG) and OmÖS under standardized standing conditions. Curvature angles were calculated using surface-based geometrical parameters derived from palpated spinous process locations. System performance was evaluated through internal calibration by comparing stepper motor-based and linear variable differential transformer (LVDT)-based measurements; validity and agreement analyses against radiographic measurements using Pearson correlation, Bland-Altman analysis, and simple linear regression, as well as test-retest reliability assessment over a two-week interval using intraclass correlation coefficients (ICCs). OmÖS demonstrated a very strong correlation with radiographic measurements for thoracic curvature angles (r= 0.974,p< 0.001) and a strong correlation for lumbar curvature angles (r= 0.852,p< 0.001). Bland-Altman analysis indicated minimal systematic bias for thoracic curvature measurements (0.13°), with limits of agreement within predefined clinically acceptable ranges. For lumbar curvature angles, agreement was characterized by slightly wider limits of agreement, but without evidence of systematic bias. Internal calibration demonstrated excellent agreement between the mechanical and electronic measurement components (r> 0.99). Test-retest reliability analysis demonstrated excellent reproducibility for both regions (ICC = 0.990), with low standard error of measurement (SEM = 0.61°) and minimum detectable change at the 95% confidence level (MDC95 = 1.70°). These findings indicate that OmÖS can provide reliable and reproducible radiation-free measurements of sagittal spinal curvature angles under standardized conditions. Whether the proposed system represents a radiation-free alternative of sagittal spinal curvature assessment for screening needs to be confirmed in future clinical studies involving larger and more diverse populations.