Assessing 3D paediatric foot morphology using low-dose biplanar radiography: Parameter reproducibility and preliminary values

Abstract

Background: The physical examination and weight-bearing radiography are the two main available methods for assessing the feet and lower limbs. The anatomy and function of these two structures interact with each other. These two assessment methods are affected by subjectivity and projection bias. Low-dose biplanar radiography (LDBR) is now a promising alternative for evaluating the lower limbs in children. At present, however, the foot cannot be assessed using LDBR. The objective of this study was to work towards developing a new method for 3D radiographic analysis of the paediatric foot during weight-bearing, first by determining the reproducibility of landmarks defined by LDBR then by reporting the values of the calculated radiographic parameters.

Hypothesis: A new radiographic method based on LDBR can be used to obtain a 3D evaluation of the foot in paediatric patients.

Patients and methods: Two biplanar radiographs in perpendicular planes were obtained simultaneously in a standardised position using the EOS system (EOS^® Imaging, Paris, France) in each of 10 healthy children. To assess measurement uncertainty, two observers performed 3D reconstructions of each of the 10 feet three times (60 reconstructions). The standard error of reproducibility of the anatomic landmarks and clinical parameters was computed. Measurement uncertainty was then estimated based on the 95% confidence interval (95%CI). To obtain reference values, the mean±SD of each variable was computed after checking that the data were normally distributed.

Results: Reproducibility was high for the anatomical landmarks of interest, calcaneal pitch angle, tibio-calcaneal angle on the lateral view, and first metatarsal pitch angle (95%CI<5%). The values of these angles in the study population are reported.

Discussion and conclusion: The data reported here pave the way towards developing new parameters for describing 3D foot morphology and for simultaneously assessing the lower limb and foot in the standing position.

Level of evidence: I.

Keywords: Foot; Paediatric patient; Parameter values; Reproducibility; Standing position; Stereoradiography.