Anterior cruciate ligament graft tear. Primary and secondary magnetic resonance signs

Magnetic resonance (MR) imaging is a useful tool for assessing the anterior cruciate ligament (ACL) graft when its integrity is in question, with some limitations. It can differentiate between a graft that is partially or completely torn. Several primary (direct) and secondary (indirect) signs have been described. Graft continuity in the coronal plane and normal graft thickness in the coronal or sagittal plane are the most valuable primary signs in excluding full thickness tear. Of the secondary signs, the anterior tibial translation and the uncovered lateral meniscus sign are the most useful in differentiating a torn from an intact graft. Some of the primary and secondary signs of a native ACL tear are yet to be assessed for accuracy in detecting grafts tear, but they are a helpful guide especially when combined. These include the deep lateral femoral sulcus, the posterior cruciate ligament (PCL) angle, and the PCL curvature values.