A comparison of the validity and reliability between a digital radiographic imaging system and manual method in measuring the Cobb angle

Abstract

Methods Twenty adolescents with scoliotic curvatures were chosen to participate in the study based on convenience, without predilection for gender, age, type or location. Images of the curvatures were examined by 15 trained observers to estimate the Cobb angle variability, as well as intraand inter-observer variations. Each image was measured three times at a minimum interval of one week between measurements by each observer. For digital measurement, a special software x-maru viewer was developed to digitally reproduce the spine assessment; for manual measurement, traditional Cobb angle measurement was used. For comparisons between manual and digital measurements, Student’s t-test was used. To determine the inter-observer and intra-observer reliabilities, the intraclass correlation coefficients (ICC) were used. For the errors in measurement, 95% prediction limits were provided. For the manual measurement of Cobb angle, a mean ICC of 0.97 was determined for intraand inter-observer reliability. For the digital measurements, a mean ICC value of 0.93 was determined for inter-observer reliability and a mean ICC value of 0.96 for intraobserver reliability.