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Validation of biplane high‐speed fluoroscopy combined with two different noninvasive tracking methodologies for measuring in vivo distal limb kinematics of the horse

Geiger, S. M., Reich, E., Böttcher, P., Grund, S., Hagen, J.
Equine veterinary journal 2018 v.50 no.2 pp. 261-269
computed tomography, gait, horses, kinematics, models, phalanges, statistical analysis, tantalum
REASON FOR PERFORMING STUDY: Biplane high‐speed fluoroscopy is a new method for gait analysis of the equine distal extremity. This is the first study validating the noninvasive tracking possibilities (Autoscoping and Scientific Rotoscoping) taking equine anatomy into account. OBJECTIVES: To determine the resolution with which Autoscoping and Scientific Rotoscoping depict motion of the equine phalanges in comparison to the invasive gold standard marker‐based registration. STUDY DESIGN: Comparative ex vivo study. METHODS: In 5 distal extremities of slaughtered ponies, 3 or 4 tantalum beads with 1 mm diameter were implanted in each of the proximal, middle and distal phalangeal bones. Three‐dimensional models of the bones were reconstructed using computed tomographic data (120 kV, 50 mA, slice thickness 1 mm, increment 0.5). The beads were digitally removed from the bone models. Biplane fluoroscopic videos were taken at 69.5 ± 3.5 kV, 102.5 ± 22.5 mA, 500 frames/s and 0.5 ms shutter speed. The 5 specimens were moved in the trial field of the biplane fluoroscopic setup in a step‐like motion (simulation of landing, main stance phase, lift‐off). Marker‐based registration, Autoscoping and Scientific Rotoscoping were carried out. For statistical analysis agreement was computed as percentiles, mean and s.d. RESULTS: The medians of Scientific Rotoscoping ranged from 0.16 to 0.66 mm in translations and 0.43 to 2.78° in rotations, while values for Autoscoping were 0.13–0.70 mm and 0.28–2.39° respectively. With 2 exceptions, all differences between methods were statistically significant. Scientific Rotoscoping is more time efficient than Autoscoping and results in smaller maximum errors. MAIN LIMITATIONS: The experimental set‐up was specifically designed to accommodate in vivo requirements. Autoscoping was not manually corrected but rather expected to work automatically. CONCLUSIONS: It is possible to noninvasively apply both Autoscoping and Scientific Rotoscoping for gait analysis of the equine phalanges with high precision. The summary is available in Chinese ‐ see supporting information.