Reliability of the Smartphone Application Inclinometer and Flexicurve in Measuring Thoracic Kyphosis

Introduction: This study examined the inter- and intra-rater reliability of the smartphone inclinometer app (SPI) and flexicurve (FC) for assessing the kyphotic angle in individuals with thoracic kyphosis (TK). Methods: This study was conducted with 60 subjects (35 males, 25 females) aged 18 to 25 who presented to Kalyon Medical Center, Gaziantep, Turkey, between December 2021 and March 2022. The subjects were evaluated by two independent assessors using FC and SPI to measure the TK angle. The intraclass correlation coefficient (ICC) was analysed at a 95% confidence interval. The level of agreement between the methods was checked using Bland-Altman analysis. Results: Inter- and intra-rater measurements were strongly correlated (ICC 0.945 and 0.964, respectively). On the Bland-Altman plots, the FC showed poor agreement with the SPI app (mean difference, 19.81° ± 2.8°). The mean kyphotic angles were 45.15 ± 6.07° and 25.34 ± 4.96°, respectively, as measured by the SPI and FC. Conclusion: This study demonstrated good intra- and inter-rater reliability of the SPI app and FC for the measurement of the spinal curvature (TK) angle in the sagittal plane. A weak agreement was discerned between the SPI and FC methods.