Intra-rater reliability of arch height ratio measurement using the navicular tuberosity on the surface of the body in children with Down syndrome

[Purpose] Flat feet frequently present in children with Down syndrome, necessitating a clinical evaluation and diagnosis. Therefore, a simple, low cost diagnostic method that can avoid radiation exposure is needed. This study was performed to investigate the intra-rater reliability of arch height ratio measurement using bone markers of the foot on the surface of the body in children with Down syndrome. [Participants and Methods] In total, 27 feet of 27 children with Down syndrome (16 male, 11 female) were included. We measured the length of each foot and the height of the navicular tuberosity on the surface of the body. The arch height ratio was calculated using the length and height. The same examiner performed three consecutive measurements of each of the two parameters. We calculated the arch height ratio using each of these measurements. The intraclass correlation coefficient [ICC(1,3)] of the length of the foot, height of the navicular tuberosity, and arch height ratio among the three measurements was obtained. [Results] The ICC of the height of the navicular tuberosity, length of the foot, and arch height ratio were quite high at 0.998, 0.999, and 0.997, respectively. [Conclusion] This study showed high intra-rater reliability of arch height ratio measurement using the length of the foot and height of the navicular tuberosity on the surface of the body in children with Down syndrome.