Intra- and inter-rater reliability of spinal flexibility measurements using ultrasonic (US) images for non-surgical candidates with adolescent idiopathic scoliosis: a pilot study

Abstract

Purpose: This study aimed to determine the intra- and inter-rater reliabilities of spinal flexibility measurements using ultrasound imaging on non-surgical candidates with adolescent idiopathic scoliosis (AIS).

Methods: Twenty-eight consecutive consented AIS subjects (25 F; 3 M) were recruited; 24 subjects' data were used for analysis. This study explored curve magnitude differences between standing, prone and voluntary maximum side-bending postures to assess the reliability of spinal flexibility (SF). Two raters were included in this study. Four flexibility indices, PRSI, BRPI, B-PRSI, BRSI, based on the postural changes from standing to prone and from prone to bending position were defined. The reliability analysis was evaluated using the intra-class correlation coefficient (ICC) [1, 2] and the standard error of measurements (SEM).

Results: The ICC [1, 2] values of the intra-rater (R2 only) and inter-rater (R1 vs R2) reliabilities of the measurements (PRSI, BRPI, B-PRSI, BRSI) were (0.82, 0.64, 0.78, 0.91) and (0.78, 0.76, 0.84, 0.94), respectively. Among the four indices, the BRPI had the highest SEM values 1.42, and 0.73 for intra- and inter-raters results, respectively, while BRSI had the lowest SEM 0.04 and 0.02 for intra- and inter-rater, respectively.

Conclusions: The BRPI, BRSI and B-PRSI could be measured reliably on US images when the Cobb angle at prone position was not close to zero. Using these three indices, information may provide more comprehensive information about the SF. Validity of spinal flexibility measurements still needed to be confirmed with a clinical study with more subjects. These slides can be retrieved under Electronic Supplementary Material.

Keywords: Adolescent idiopathic scoliosis; Flexibility indices; Reliability; Spinal flexibility; Ultrasound imaging.