Interobsever Variability of Measurements for Flatfoot Deformity Using High Resolution Weightbearing Cone-Beam CT Examination According to Reader Experience

Category: Other Introduction/Purpose: To evaluate interobserver reliability among readers of different clinical experience by applying measurements for adult acquired flatfoot deformity (AAFD) using high-resolution three-dimensional (3D) weightbearing (WB) cone-beam CT (CBCT) examination. Methods: In this IRB approved study, 20 patients with flexible AAFD [12 male, 8 female; mean age 54.2 (20-88) years] were scanned with standing (weightbearing) CTs. Two blinded observers, a medical student and a foot/ankle surgeon, applied validated AAFD measurements in sagittal, coronal, and axial planes using predefined anatomical landmarks. Interobserver reliability was calculated using Pearson correlation. Results: There was significant interobserver agreement with high correlation for the following measurements(p < 0.0001): distances between medial cuneiform to-floor (r=0.981) and to-skin (r=0.986), navicular to-floor (0.992) and to-skin (r=0.900); cuboid to-floor (r=0.975) and to-skin (r=0.978), and calcaneus-to-fibula (r=0.808); calcaneal inclination angle (r=0.795); forefoot arch angle (r=0.983); and subtalar horizontal angles at 25%, 50%, and 75% of the anteroposterior joint length (r=0.784, 0.891, 0.809). Significant agreement with moderate correlation was additionally demonstrated for talar-first metatarsal angle (r=0.553, p < 0.014), medial cuneiform-first metatarsal angle (r=0.668, p < 0.001), and navicular-cuneiform angle (r=0.746, p < 0.0002). Level of training did not influence the reliability of any measurements except medial cuneiform-first metatarsal angle (specialist: 8.83°; student: 1.61°; p < 0.01). Statistically insignificant difference between readers (p>0.05) was noted in mean talar-first metatarsal and subtalar horizontal angles. Conclusion: While literature describes large variability for AAFD measurements from plain radiographs among readers of varying medical experience, 3D WB CBCT can yield similar measurements using predefined planes with high reliability, independent of reader experience.