Indirect Signs of Magnetic Resonance Imaging of the Knee with Anterior Cruciate Ligament Tears: Comparison between Acute and Chronic ACL Tears

Koo, Bon Seop; Kim, Kyung Chul; Choi, Jae Yeul; Jeong, Hwa Jae; We, Seong Tai

Abstract

PURPOSE
The purpose of this study was to assess the differential features of indirect signs at magnetic resonance (MR) imaging in acute and chronic tears of the anterior cruciate ligament.
MATERIALS and METHODS
Preoperative MR imagings of 71 patients (71 knees) who were confirmed as complete tear of anterior cruciate ligament (ACL) by arthroscopy were evaluated. On MR imagings of acute (n=47) and chronic (n=24) tear of ACL, and of the control group (n=31) , we reviewed bone bruise, posterior displacement of the lateral meniscus, posterior cruciate ligament (PCL) angle, and PCL line.
RESULTS
Bone bruise was observed in 35 cases (74.5%) at acute tear and in 9 (37.5%) at chronic tear, and mean PCL angle was 122 and 106 degrees, respectively. These two signs were significantly different (p<0.05) . The presence of posterior displacement of lateral meniscus was in 26 cases (55.3%) at acute tear and in 12 (50.0%) at chronic tear. Positive PCL line was in 23 (48.9%) and in 16 (66.7%) cases, respectively.
CONCLUSION
Bone bruise, posterior displacement of lateral meniscus, PCL angle, and PCL line were helpful indirect signs suggesting an ACL tear in MR imagings. Posterior displacement of lateral meniscus and PCL line were not affected by the time of ACL tear. Bone bruise in acute tear and PCL angle in chronic tear were very frequent.