Magnetic resonance imaging of surgically confirmed anterior cruciate ligament graft disruption.

OBJECTIVE

To evaluate previously described primary and secondary MRI signs of disruption to anterior cruciate ligament (ACL) grafts in surgically proven cases.

MATERIALS AND METHODS

We retrospectively analyzed MR images of 48 patients (mean age 29 years) with clinically suspected ACL graft disruption. All patients had surgical confirmation of the MRI findings. The reviewers analyzed the cases blinded to the surgical results and assessed each of the primary and secondary MRI signs of graft disruption individually. Subsequently, a final impression of the graft integrity based on a comprehensive assessment of all of the primary and secondary findings was made.

RESULTS

Utilizing a comprehensive assessment of previously described primary and secondary MR findings of ACL graft disruption, the blinded reviewers were able to identify correctly full-thickness graft tears with test accuracy of 85%, sensitivity of 72%, and specificity of 100%. Individual assessment of the primary finding of graft fiber discontinuity had sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 72%, 100%, 100%, 77% and 85%, respectively, for full-thickness tears. Other individual primary and secondary findings were less reliable; however, the primary findings of marked segmental thinning of the graft and markedly abnormal graft orientation, and the secondary findings of bone contusions in the lateral compartment and large joint effusion, had high specificity and positive predictive value. Of the four missed cases, two had associated arthrofibrosis.

CONCLUSION

The comprehensive assessment of previously described primary and secondary MRI findings of ACL graft disruption has high test specificity and moderately high test accuracy. The presence of graft fiber discontinuity is the most reliable primary or secondary finding when assessed individually. Marked segmental thinning of the graft and abnormal fiber orientation, and the presence of bone contusions in the lateral compartment and large joint effusion, are less reliable overall but are highly suggestive of full-thickness graft tear when present.