Comparison of radiographic and anatomic femoral varus angle measurements in normal dogs.
OBJECTIVE
To determine if the clinically practiced method of radiographic femoral varus angle (R-FVA) measurement is repeatable, reproducible, and accurate.


METHODS
Radiographic and anatomic study. ANIMALS/SAMPLE POPULATION: Normal Walker hound cadavers (n=5) and femora (n=10).


METHODS
Cadavers were held in dorsally-recumbent and torso-elevated positions as 3 craniocaudal radiographs were made of each femur, by each of 2 different technicians. Femora were then harvested for direct measurement of anatomic femoral varus angle (A-FVA). R-FVA was measured on each radiograph by each of 3 examiners on 3 separate occasions. Intra-observer (repeatability) and inter-observer (reproducibility) variance in R-FVA measurement and the strength of relationship between R-FVA and A-FVA (accuracy) were determined.


RESULTS
Mean (+/-SD) A-FVA was 5.2+/-2.1 degrees (range, 2.4-8.2 degrees). Mean (+/-SD) R-FVA was 5.8+/-1.0 degrees (range, 2.7-9.6 degrees). Intra-observer variance (range: 11-16%) and inter-observer variance (16%) were acceptable. The strength of relationship between measured R-FVA and A-FVA (maximum adjusted R(2)<0) was unacceptably low regardless of observer, patient position, or radiographic technician.


CONCLUSIONS
R-FVA measurement was repeatable and reproducible, but not statistically accurate in predicting A-FVA in these 5 normal Walker hounds. The detected inaccuracy may be real or the result of a selection bias for normal dogs obscuring the true relationship.


CONCLUSIONS
R-FVA may not be an accurate method of femoral varus measurement in dogs with A-FVA<10 degrees. Using Slocum's criteria for distal femoral osteotomy (R-FVA>10 degrees), the procedure would not have been erroneously performed in any of the normal dogs of this study.
Swiderski
Jennifer K
JK
Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA.
Radecki
Steven V
SV
Park
Richard D
RD
Palmer
Ross H
RH
D000818:Animals; D002102:Cadaver; D004285:Dogs / Q000033:anatomy & histology*; D005269:Femur / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D015588:Observer Variation; D011859:Radiography / Q000379:methods / Q000592:standards / Q000662:veterinary*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity