EFFECT OF RADIOGRAPHIC POSITIONING ON INTERPRETATION OF CUBITAL JOINTCONGRUITY IN DOGS

Objective-To ascertain effects of x-ray beam centering and limb positi on on apparent congruity of a normal cubital joint (elbow). Animals-6 skeletally mature male Treeing Walker Coonhounds without physical, rad iographic, or gross evidence of elbow abnormalities. Procedure-Relativ e movement among humerus, radius, and ulna and measured joint space wi dth on mediolateral and craniocaudal radiographic views was compared, using various x-ray beam centering and limb positions. Results-Highest agreement and greatest certainty on subjective determination of congr uity was for the flexed 90 degrees mediolateral radiographic view with the xray beam centered on the elbow. Distortion artifact of the proxi mal ulnar measurements was significant when the x-ray beam was centere d on the midpoint of the radius. On the mediolateral view, the humeror adial 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 an gled +30 degrees toward the humerus. Conclusions-Artifact distortion o f joint width affected objective and subjective assessment of elbow co ngruity when the limb was placed in extreme flexion or extension or wh en 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 w as slightly angled toward the humerus. Clinical Relevance-Elbow congru ity was best assessed on the flexed 90 degrees lateral radiographic vi ew with the x-ray beam centered on the joint.