Comparison of tibial plateau angles in dogs with unilateral versus bilateral cranial cruciate ligament rupture: 150 cases (2000-2006)

Objective - To compare tibial plateau angle (TPA) in dogs with unilateral versus bilateral cranial cruciate ligament (CCL) rupture, to compare right versus left TPA in dogs with bilateral CCL rupture, and to determine whetherTPA can be used to predict whether a dog with unilateral CCL rupture would subsequently rupture the contralateral CCL. Design - Retrospective case series. Animals - 150 dogs with unilateral (n = 58) or bilateral (92) CCL rupture. Procedures - Medical records were reviewed and TPA was recorded. Dogs with unilateral CCL rupture that were not known to have ruptured the contralateral ligament were followed up for a minimum of 2 years. Results - Dogs with unilateral CCL rupture were significantly older (median, 7.0 years) than dogs with bilateral CCL rupture (median, 4.5 years). Median TPA for dogs with unilateral CCL rupture (26°) was not significantly different from median TPA for dogs with bilateral rupture (27° in both the right and left limbs), and right and left TPAs were not significantly different in dogs with bilateral CCL rupture. There was no correlation between TPA and the time interval between diagnosis of the initial and subsequent CCL ruptures in dogs with bilateral CCL rupture. Conclusion and Clinical Relevance - Results suggested that TPA in the range studied (mostly < 35°) was not a useful predictor of contralateral CCL rupture among dogs with unilateral CCL rupture, although age may be a risk factor for development of bilateral CCL rupture. The incidence of bilateral CCL rupture may be higher than previously reported.