Effect of sagittal plane positioning errors on measurement of the angle of inclination in dogs

Angles of inclination were calculated from ventrodorsal (VD) and caudocranial horizontal beam (CaCrHB) radiographs of 17 anesthetized dogs, and from radiographs of left femurs of the same dogs positioned 0 degree, 10 degrees, 15 degrees, and 20 degrees from the cassette in the sagittal plane. Angles of inclination also were measured directly from radiographs of the bones rotated to correct for anteversion. Calculated angles of inclination from the bones at 10 degrees, 15 degrees, and 20 degrees from the cassette were significantly different from the 0 degree values obtained by calculation and direct measurement. Inclination angles from live dogs were consistently larger than those from 0 degree bones. Differences between angles of inclination calculated from VD and CaCrHB radiographs of live dogs were not significant.