EQUINE VETERINARY EDUCATION Equine vet. Educ. (2022) 34 (11) 581 doi: 10.1111/eve.13554_1


Original Article


The position of x-ray beam centring affects radiographic measurements of palmar angle and sole thickness on radiographs of the equine thoracic distal limb


E. Staples†,*, E. Porter‡, P. Mendoza‡, K. Trolinger-Meadows†, J. Colee§ and A. Morton†


†Department Large Animal Clinical Sciences; ‡Department Small Animal Clinical Sciences, College of Veterinary Medicine; and §College of Agriculture and Life Sciences, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, Florida, USA *Corresponding author email: dr.ellenstaples@canopyequine.com


M. Staples's present address: Equine Medical Center of Ocala Ocala, Florida, USA Keywords: horse; radiography; podiatry; hoof; laminitis


Summary


Background Different locations of x-ray beam centring on the equine distal limb for lateromedial and dorsopalmar radiographs of the equine digit may affect clinically relevant radiographic measurements.


Objectives To evaluate the effects of two different locations of x-ray beam centring on lateromedial and dorsopalmar radiographic measurements of the equine digit and to assess intra- and inter-observer variability of measurements.


Study design Prospective, observational and method comparison.


Methods Comparisons were made of nine measurements on orthogonal radiographs acquired from 24 unshod equine feet at two locations of x-ray beam centring: coronary band and hoof-ground interface. Radiographic measurements were obtained by three observers of varied equine veterinary experience and made in triplicate by a board-certified veterinary radiologist.


Results Radiographs acquired with x-raybeamcentred at the coronary band and hoof-ground interface produced differences in the mean measurements of palmar angle, defined as the angle created by the palmar processes of the distal phalanx relative to the ground surface, on the lateromedial projection (p = 0.002), and medial (p < 0.001) and lateral (p < 0.001) sole thickness on the dorsopalmar projection. There was less variability of palmar angle (p = 0.039) and more superimposition of the palmar processes (p < 0.001) with the x-raybeamcentred at the hoof-ground interface.


Main limitations The study population was homogeneous and only included horses without outwardly visible abnormalities of the foot. Anatomic measurements were not used for comparison due to the nonterminal nature of the study.


Conclusions Centring the x-ray beam at the hoof-ground interface produces more repeatable and smaller radiographic measurements of palmar angle and sole thickness when compared to centring the x-ray beam centred at the coronary band. The distal phalangeal palmar processes are more superimposed with the more distal x-ray beam centring. The strong inter- and intra-observer variability support the use of these nine radiographic measurements by practitioners of all levels of experience.


Clinical relevance


• Consistent protocols are important in serial radiographic evaluation of the equine foot.


• Practitioners of different experience levels produce similar radiographic measurements for nine measurements of the equine digit.


• Centring the x-ray beam at the hoof-ground interface allows for more superimposition of the palmar processes and produces smaller and less variable radiographic measurements of palmar angle and medial and lateral sole thickness when compared to centring at the coronary band; however, the point of x-ray beam centre has less effect on other commonly performed measurements of the equine foot.


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