Can magnetic resonance imaging findings predict the degree of knee joint laxity in patients undergoing anterior cruciate ligament reconstruction?

Abstract

Background: The present study was performed to determine whether MRI findings can predict the degree of knee joint laxity in patients undergoing ACL reconstruction and whether the accuracy of the prediction is affected by the MRI acquisition time.

Methods: We assessed prospectively collected data of 154 knees with ACL tears. The presence or absence of four primary findings of ACL tears, i.e., nonvisualization, discontinuity, abnormal signal intensity, and abnormal shape of the ACL, and five secondary findings, i.e., anterior translation of the tibia relative to the femur (≥7 mm), posterior cruciate ligament angle (<105°), bone contusion, Segond fracture, and the deep sulcus sign, were determined. Knee joint laxity was assessed using the Lachman and pivot shift tests. The associations between MRI findings and clinically assessed knee joint laxity were analyzed and compared between subgroups (≤3 months from injury to MRI, 89 knees; >3 months, 65 knees).

Results: Nonvisualization was related to the results of the Lachman test [Odds ratio (OR), 2.6; 95% confidence interval (CI), 1.2-5.5]. Anterior translation of the tibia relative to the femur was related to the results of the pivot shift test (OR, 3.8; 95% CI, 1.6-9.4). In subgroup comparisons of the early and late MRI groups, anterior translation of the tibia relative to the femur was related to the results of the pivot shift test in the early MRI group (OR, 4.5; 95% CI, 1.4-14.4). In contrast, no MRI findings had statistically significant relationships with physical findings in the late MRI group.

Conclusions: Our study indicates that MRI findings may have some usefulness for predicting the grade of knee laxity in patients with symptomatic ACL injury, but its value is limited, especially in patients with a longer time interval between injury and the performance of MRI.

Figure 1

In this proton density sagittal image, no anterior cruciate ligament (ACL) is seen in the notch of the knee (arrow). Nonvisualization is defined as a failure to visualize the ACL on the image.

Figure 2

In this T2-weighted fat-suppressed sagittal image, discontinuity of anterior cruciate ligament (ALC) fibers is shown (arrow). Discontinuity is defined as a focal gap or interruption of the ACL fibers.

Figure 3

In this T2-weighted fat-suppressed sagittal image, abnormal signal intensity is observed as increased signal intensity within the anterior cruciate ligament (arrow).

Figure 4

In this proton density sagittal image, an abnormal shape is observed, which is defined as an irregular, wavy contour of the margin of the anterior cruciate ligament.

Figure 5

Sagittal fat-suppressed T2-weighted image shows bone contusions in the lateral femoral condyle and posterolateral tibia plateau.

Figure 6

The posterior cruciate ligament angle (PCL) is determined as the angle between the lines drawn through the central portion of the tibial and femoral insertions of the PCL. An angle of <105° is considered to be a positive indicator of ACL injury.

Figure 7

Anterior translation of the tibia relative to the femur is measured through the middle of the lateral femoral condyle on sagittal images. Two lines are drawn parallel to the cephalocaudal axis of the image: one crossing the posteriormost point of the posterolateral tibia plateau and the other crossing the posteriormost point of the lateral femoral condyle. Anterior translation is determined by the distance in millimeters between these two lines. A translation of ≥7 mm is considered to be a positive indicator of ACL injury.