Reliability and Convergent Validity of Digital Photography in Assessing Postural Orientation of Children with Cerebral Palsy: A Methodological Study

Background: This study aimed to assess the test-retest intra-rater reliability and convergent validity of digital photography (DP) in detecting the postural orientation of children with cerebral palsy (CP). Methods: The study recruited children with various types of CP with the Gross Motor Function Classification System level I or II and spasticity < 2 on the Ashworth Scale, without any visual or cognitive impairments. Children who had undergone any surgical intervention or received a botulinum toxin injection within the previous six months were excluded. A digital camera was fixed at 1.5 meters from the participants at the height of 90 cm. Non-reflective markers were attached to eight anatomical landmarks to localize the upper and lower center of mass on both sides. The same examiner took three digital photos to detect intra-rater reliability using the intraclass correlation coefficient (ICC). Pearson's correlation and linear regression analysis were used to assess the convergent validity of the DP method compared with the Pediatric Balance Scale (PBS) scores. Results: Thirty children (7.44 ± 2.38 years) were assessed to test the reliability of DP, and 55 others (8.06 ± 2.19 years) participated in the convergent validity study. Intra-rater reliability was found to be perfect (ICC > 0.995) and there was a strong significant negative correlation between DP measures and PBS scores (Pearson's correlation > 0.75) with high adjusted R2 (R2 > 0.567), indicating goodness of fit between the measures. Conclusions: Digital photography (DP) is a reliable and valid method for assessing postural orientation in children with various types of CP.