Tibial Plateau Angle Measurement in Dogs - Comparison of Three Different Methods

The aim of this study was to establish two new methods for measuring the tibial plateau angle (TPA): proximal tibial circle (PTC) as well as full tibial circle (FTC) method, and to test their reliability in comparison to the classical method (CM). Three radiologists implemented each method, and measurements were repeated three times. The results of consecutive measurements obtained by two observers had excellent reliability with an interclass correlation coefficient (ICC) greater than 0.9 for all methods, while measurements obtained by the third observer had good reliability for the CM (ICC=0.885) and PTC method (ICC=0.851). The results obtained by the three observers for all methods indicate good reliability for the PTC and FTC methods (ICC=0.848 and 0.880, respectively) and excellent reliability for CM (ICC = 0.909); the results of the different observers for each method were not significantly different. The significant difference resulting from the applied measurement method (ICC = 0.447 and P<0.01) was confirmed. Statistically significant differences were not found between the CM and PTC method (P>0.05), while differences between the PTC and FTC, as well as CM and FTC methods, were statistically significant (P<0.01). New methods for TPA measurements based on shorter tibial axes may be an alternative to a method based on the full-length axis. A high correlation between the methods indicates the precision of each of them. Newly established methods can be used when the tarsal joint is not included in radiographs or is affected by degenerative changes, making use of the classical method not possible.