Accuracy of a radiographic stitching technique to measure tibial plateau angle in large and giant breed dogs.

Objective: To determine if a novel radiographic stitching technique yields accurate tibial plateau angle (TPA) measurements in large and giant breed dogs. Methods: Three medio-lateral digital radiographic projections (traditional TPLO, stifle-centred, tarsus-centred) were obtained from each of 17 pairs of pelvic limbs from skeletally mature large and giant breed dogs. Eight observers performed image stitching followed by TPA measurements on the stitched (sTPA) and traditional radiographs (tTPA). The TPA was also measured on photographs made of isolated anatomical tibial specimens (aTPA). Measurements were compared between observers and between image type using ANOVA and correlation coefficients. Results: There was no statistically significant difference in TPA between observers for tTPA or sTPA radiographs (p >0.05); both sTPA and tTPA were highly correlated with aTPA and with each other (r = 0.88, 0.89, and 0.97 respectively). Clinical relevance: This novel digital stitching method provides an alternative technique for accurately measuring TPA utilizing a stifle-centred radiograph that may be useful when traditional TPLO radiographs are difficult to obtain. This may be particularly useful in large and giant breed dogs because collimation to include the entire tibial length can preclude proper centring of the radiographic beam over the stifle.