Tibial plateau morphology in dogs with cranial cruciate ligament insufficiency

Objective: To identify possible biomechanical causes for the predominantly unilateral presentation of cranial cruciate ligament (CCL) insufficiency by comparing the computed tomographic (CT) features of the tibial plateau of CCL affected and contralateral sound stifles in dogs with unilateral CCL insufficiency. Study design: Cross-sectional study. Animals: Eighteen dogs, 36 stifles. Methods: Eighteen dogs with naturally occurring unilateral CCL insufficiency were included. Stifle CT and radiographs were performed at the time of diagnosis. Follow-up was performed at a minimum of 1 year from the original diagnosis to ensure that there was no evidence of contralateral CCL insufficiency. The medial tibial plateau angle (m-TPA), lateral TPA (and l-TPA), medial tibial plateau midsagittal radius of curvature (m-TPr), and lateral TPr (l-TPr) were measured from the CT images. Variables were compared with paired t tests. A Bonferroni correction was performed, and P < .006 was considered significant. Results: Mean m-TPr was steeper (P = .002) and m-TPr: l-TPr ratio was greater (P < .001) in affected stifles compared with contralateral sound stifles. No other variables differed between groups. Mean l-TPA was steeper than mean m-TPA (P < .001). Conclusion: Tibial plateau convexity differed between the CCL affected and contralateral sound stifle in dogs with unilateral CCL insufficiency. Clinical significance: Medial tibial plateau convexity may play a role in the development of CCL insufficiency.