Abstract
ObjectivesWe hypothesize that three-dimensional (3D) geometric analyses in weight bearing CT-images of the foot and ankle are more reproducible compared to two-dimensional (2D) analyses. Therefore, we compared 2D and 3D analyses on bones of weight-bearing and non weight-bearing cone-beam CT images of healthy volunteers. MethodsTwenty healthy volunteers (10 male, 10 female, mean age 37.5 years) underwent weight-bearing and non weight-bearing cone-beam CT imaging of both feet. Clinically relevant height and angle measurements were performed in 2D and 3D (for example: cuboid height, calcaneal pitch, talo-calcaneal angle, Meary's angle, intermetatarsal angle). Three-dimensional measurements were obtained using automated software. Intra-observer and inter-observer agreement were evaluated for all 2D measurements. ResultsOverall intraclass correlation coefficients (ICC’s) were higher than 0.750 for most 2D measurements, ranging from 0.352 to 0.995. Calcaneal pitch, angle between the first metatarsal (MT1) and proximal phalange 1, between the fifth metatarsal (MT5) and the calcaneus and heights of the sesamoid bones, navicular, cuboid and talus decreased during weight-bearing in both 2D and 3D results (p < 0.01). Meary’s angle was not statistically different in 2D (p = 0.627) and 3D (p = 0.765). Higher coefficients of variation in 2D geometric analysis parameters (0.27 versus 0.16) indicate that 3D analyses are more precise compared to 2D (p < 0.01). Results of left and right feet are comparable for 2D and 3D analyses. ConclusionAlthough 2D and 3D geometrical analyses are fundamentally different, automated 3D analyses are more reproducible and precise compared to 2D analyses. In addition, 3D evaluation better demonstrates differences in bone configurations between weight-bearing and non weight-bearing conditions, which may be of value to demonstrate pathology.
Highlights
Conventional CT and radiography help clinicians recognize and locate problems in the foot and ankle
We propose to evaluate geometrical parameters extracted from 3D weight-bearing and non weight-bearing images as well as 2D radiogram equivalents extracted from 3D volume data, which enables a fair 2D versus 3D comparison [2,12].; The ob jectives of this study were to compare 2D with 3D geometrical param eters, compare these parameters in weightbearing and non weight-bearing conditions, and between the left and right feet
Coefficient of variation was calculated to determine the precision of 2D and 3D measurements
Summary
Conventional CT and radiography help clinicians recognize and locate problems in the foot and ankle. To assess pathological foot morphology, weight-bearing radiography is often used in standard care in patients with Charcot foot, diabetic foot or neuropathic foot, where severe deformities of the foot result in a change of anatomy and response of inter-bone alignment as a result of loading [1,2,3]. In a weight-bearing cone-beam CT (CBCT) scanner, 3D images of the lower extremities can be acquired with natural loading and without load in the upright position. This type of functional imaging may reveal problems that would otherwise be non-discernible [4,5,6,7,8], such as the displacement and rotation of bone fragments in patients with
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