Effect of tibial rotation on the tibial plateau angle measurement in dogs: An ex vivo study

Objective To determine the effect of tibial rotation on radiographic tibial plateau angle (TPA) measurement in normal and cranial cruciate ligament (CrCL)‐deficient stifles. Study design Cadaveric study. Sample population Five pairs of canine cadaver hind limbs with no stifle osteoarthritis. Methods Mediolateral radiographs of each specimen were obtained at 0°, 10°, 20°, and 30° of internal and external rotation of the tibia with both intact and transected CrCL. Two Kirschner wires were placed at the cranial and caudal landmarks of the tibial plateau, and the 0° views were imaged again, representing the anatomic TPA. Five observers measured the TPA twice on all images. Measurements were compared by using a mixed‐model ANOVA. Intraobserver and interobserver variability were evaluated by using the coefficient of variation. Results Tibial plateau angle did not differ among the anatomic, CrCL‐intact, and CrCL‐deficient 0° views or between the CrCL‐intact and CrCL‐deficient views at the various tibial rotations. The only difference detected was between CrCL‐intact stifles radiographed at 0° and external rotation (range, 1.16°‐1.6°; P = .016, P = .001, and P .05). Conclusion In CrCL‐deficient stifles, tibial rotation of up to 30° internally and externally did not result in clinically relevant changes in TPA measurements. Clinical significance The TPA can be successfully measured with up to 30° of internal and external tibial rotation in CrCL‐deficient stifles with no osteoarthritic changes.