Development and Validation of a Mobile Application for Measuring Femoral Anteversion in Patients With Cerebral Palsy

Abstract

Background: Computed tomography (CT) provides benefits for 3-dimensional (3D) visualization of femur deformities. However, the potential adverse effects of radiation exposure have become a concern. Consequently, a biplanar imaging system EOS has been proposed to enable reconstruction of the 3D model of the femur. However, this system requires a calibrated apparatus, the cost of which is high, and the area occupied by it is substantial. The purpose of this study was to develop a mobile application that included a new method of 3D reconstruction of the femur from conventional radiographic images and to evaluate the validity and reliability of mobile the application when measuring femoral anteversion. Methods: The statistical shape model, graph-cut algorithm, and iterative Perspective-n-Point algorithm were utilized to develop the application. The anteroposterior and lateral images of a femur can be input using the embedded camera or by file transfer, and the touch interface aids accurate contouring of the femur. Regarding validation, the CT scans and conventional radiographic images of 36 patients with cerebral palsy were used. To evaluate concurrent validity, the femoral anteversion measurements on the images reconstructed from the mobile application were compared with those from the 3D CT images. Three clinicians assessed interobserver reliability. Results: The mobile application, which reconstructs the 3D image from conventional radiographs, was successfully developed. Regarding concurrent validity, the correlation coefficient between femoral anteversion measured using 3D CT and the mobile application was 0.968 (P<0.001). In terms of interobserver reliability, the intraclass correlation coefficient among the 3 clinicians was 0.953. Conclusions: The measurement of femoral anteversion with the mobile application showed excellent concurrent validity and reliability in patients with cerebral palsy. The proposed mobile application can be used with conventional radiographs and does not require additional apparatus. It can be used as a convenient technique in hospitals that cannot afford a CT machine or an EOS system. Level of Evidence: Level III—diagnostic.

Coronal and Transverse Malalignment in Pediatric Patellofemoral Instability

“…Limb-alignment MRI protocols have been developed which have decreased exam time requirements, though the relative cost of an MRI remains a significant consideration in the US healthcare system [ 46 , 57 ]. Sung et al developed and validated a mobile application that can reliably measure femoral anteversion from AP and lateral femur radiographs [ 58 ]. In an MRI study comparing a population of patients with recurrent patellar dislocations and controls, Maine et al quantified the rotational alignment of the extensor mechanism, known as the quadriceps torsion angle (QTA).…”

Accuracy of CT for measuring femoral neck anteversion in children with developmental dislocation of the hip verified using 3D printing technology

“…A lot of authors think that 2D-CT method is to use 2D images to measure the 3D structure, which is obviously inaccurate, as 2D images cannot simultaneously show the complete structure of the proximal femur [ 29 , 30 ]. Besides, in 2D-CT measurement method, it is more random and subjective in selection of CT slice images for measurement, which leads to great differences in measurement results between different physicians [ 31 , 32 ]. In this study, it is found that the difference in results between 3D-PF model and 2D-CT measurement was statistically significant, indicating that the accuracy of 2D-CT measurement method was not very good.…”

Accuracy of CT for Measuring Femoral Neck Anteversion in Children With Developmental Dislocation of the Hip Verified Using 3D Printing Technology

“…A lot of authors think that 2D-CT method is to use 2D images to measure the 3D structure, which is obviously inaccurate, as 2D images cannot simultaneously show the complete structure of the proximal femur [26]. Besides, in 2D-CT measurement method, it is more random and subjective in selection of CT slice images for measurement, which leads to great differences in measurement results between different physicians [27,28]. In this study, it is found that the difference in results between 3D-PF model and 2D-CT measurement was statistically signi cant, indicating that the accuracy of 2D-CT measurement method was not very well.…”