Comparison of radiographic assessments of the tibial plateau slope in dogs

Objectives-To evaluate the accuracy of 2 radiographic methods used to assess tibial plateau slope (TPS) in dogs and evaluate effects of film digitization and radiographic beam placement on TPS measurements. Sample Population-16 hind limbs from dog cadavers weighing > 20 kg. Procedures-Radiographs of tibiae were made with the radiographic beam centered over the stifle joint and midshaft of the tibia. Tibiae were collected, the femorotibial contact area was determined, and slope of the medial tibial condyle in relation to the tibial shaft was measured. Radiographs were digitized. Slope of the medial tibial condyle was measured on printed and digitized radiographs read in random order by 6 examiners unaware of anatomic measurements. Three examiners used a conventional measuring technique, and 3 examiners used an alternative measuring technique. Results-Anatomic measurements were significantly higher than radiographic measurements made by use of the conventional interpretation method but did not differ from radiographic measurements made by use of the alternate method. Measurements from printed radiographs were lower than measurements from digitized radiographs for the 4 most experienced examiners. Conclusions and Clinical Relevance-Measurements made by use of a line tangential to the cranial, linear portion of the medial tibial condyle at the femorotibial contact point were accurate measurements of the anatomic TPS. Measurements made by use of the conventional TPS measurement method underestimated the anatomic TPS. Measurements made on digitized radiographs were typically more accurate than measurements made on printed radiographs.