COMPLETE VS PARTIAL-THICKNESS TEARS OF THE POSTERIOR CRUCIATE LIGAMENT - MR FINDINGS

Objective: We sought to define the MRI appearance of both complete and partial-thickness tears of the posterior cruciate ligament (PCL) and to describe patterns of injury and associated MRI findings. Materials and Methods: Three radiologists retrospectively reviewed MR images and medical records on 32 patients with PCL tears (15 complete, 17 partia l) and correlated MRI findings to results of clinical testing and surg ery. Results: The PCL had indistinct margins in 27 (84%) of 32 patient s and was abnormally thick in 25 (78%) patients. In 31 (97%) patients, the torn PCL showed increased signal intensity on both T1- and T2-wei ghted pulse sequences. Although there was no statistically significant difference between patients with complete tears and those with partia l tears with regard to thickness, margination, and signal intensity of the PCL, MR images in patients with complete tears were more likely t o show focal areas of ligamentous discontinuity (10 of 15 cases) (p = 0.01). Associated knee injuries were seen in 21 (66%) patients and wer e seen more frequently in patients with complete PCL tears (p = 0.015) . Bony injury (n = 11, 34%) and tears of the medial collateral ligamen t(n = 13, 41%) and menisci (n = 10, 31%) were common. No specific patt ern of bony injury was found. Conclusion: Posterior cruciate ligament tears can be diagnosed readily by multiplanar MRI using both morpholog ical and signal intensity characteristics. Although differentiation be tween complete and partial-thickness PCL tears by MRI criteria alone i s more problematic, complete tears are more likely to show focal areas of discontinuity and partial tears are more likely to show at least s ome intact fibers.