Effect of radiographic positioning on interpretation of cubital joint congruity in dogs

To ascertain effects of x-ray beam centering and limb position on apparent congruity of a normal cubital joint (elbow). 6 skeletally mature male Treeing Walker Coonhounds without physical, radiographic, or gross evidence of elbow abnormalities. Relative movement among humerus, radius, and ulna and measured joint space width on mediolateral and craniocaudal radiographic views was compared, using various x-ray beam centering and limb positions. Highest agreement and greatest certainty on subjective determination of congruity was for the flexed 90 degrees mediolateral radiographic view with the x-ray beam centered on the elbow. Distortion artifact of the proximal ulnar measurements was significant when the x-ray beam was centered on the midpoint of the radius. On the mediolateral view, the humeroradial joint space became significantly wide when the elbow was flexed. On the craniocaudal view, maximal humeroradial joint space width was obtained when the x-ray beam bisected the angle of the joint or was angled +30 degrees toward the humerus. Artifact distortion of joint width affected objective and subjective assessment of elbow congruity when the limb was placed in extreme flexion or extension or when the x-ray beam was not centered over the area of interest. Optimal visualization of the humeroradial joint space on the craniocaudal view was achieved when the x-ray beam bisected the angle of the elbow or was slightly angled toward the humerus. Elbow congruity was best assessed on the flexed 90 degrees lateral radiographic view with the x-ray beam centered on the joint