Sensitivity of radiographic evaluation of radio-ulnar incongruence in the dog in vitro.
OBJECTIVE
To determine the sensitivity and specificity of radiographic evaluation of radio-ulnar incongruence in canine elbow joints in vitro.


METHODS
Radiographic evaluation of induced radio-ulnar incongruence in canine cadaveric forelimbs by radiologists blinded to study design.


METHODS
Six cadaveric canine left forelimbs.


METHODS
Extended lateral, 90 degrees flexed lateral, and cranio-caudal projections were taken of the elbow joint of six cadaveric canine forelimbs. A four-pin, type I external skeletal fixator (ESF) with a linear motor side bar was attached to the medial aspect of the radius, and a 2-cm segment of bone was removed from the mid-diaphysis. A 3.5-mm cortical bone screw placed from the medial to lateral styloid processes prevented relative movement between the distal radius and ulna during radial shortening. The ESF was used to progressively shorten the radius in increments of 0.5 mm to a total of 4 mm. The three radiographic projections were repeated after each incremental change of length. After the study, each elbow joint was disarticulated to confirm the presence of a step defect. The original radiographs and three copies were randomized and then evaluated by four radiologists blinded to the study design. Radiologists were asked to evaluate whether the joint was normal or abnormal and if there was evidence of radio-ulnar incongruence. The ability of each radiologist to correctly identify congruent elbows (specificity) and incongruent elbows (sensitivity) was calculated.


RESULTS
The median specificity was 86% using the lateral projection and 82% using the cranio-caudal projection. The median sensitivities using the lateral and cranio-caudal radiographic projections were 78% and 79%, respectively. The degree of radial shortening required for individual radiologists to achieve a sensitivity of 90% ranged from 1.5 mm to greater than 4 mm.


CONCLUSIONS
Standard radiographic evaluation for radio-ulnar incongruence in the dog may be associated with relatively poor sensitivity and specificity. Invasive surgical procedures and screening programs that rely on radiographic diagnosis of radio-ulnar incongruence should be discouraged until a more reliable method of diagnosis of this type of elbow joint incongruence is available.
Mason
David R
DR
Department of Surgical and Radiological Sciences, University of California at Davis, Davis, CA 95616, USA.
Schulz
Kurt S
KS
Samii
Valerie F
VF
Fujita
Yukihiro
Y
Hornof
William J
WJ
Herrgesell
Eric J
EJ
Long
Craig D
CD
Morgan
Joe P
JP
Kass
Phillip H
PH
D000818:Animals; D004283:Dog Diseases / Q000000981:diagnostic imaging*; D004285:Dogs; D005552:Forelimb / Q000000981:diagnostic imaging*; D004204:Joint Dislocations / Q000000981:diagnostic imaging / Q000662:veterinary*; D015588:Observer Variation; D011859:Radiography; D011884:Radius / Q000000981:diagnostic imaging; D012680:Sensitivity and Specificity; D014457:Ulna / Q000000981:diagnostic imaging