Sensitivity and specificity of vertically oriented lateral collateral ligament as an indirect sign of anterior cruciate ligament tear on magnetic resonance imaging

To evaluate the correlation between anterior cruciate ligament (ACL) tear and straightened, vertically oriented lateral collateral ligament (LCL).

This study included 556 patients who underwent MRI of the knee and were divided into three subsets based on ACL morphology. Subset 1 included patients with unequivocal normal ACL. Subset 2 included patients with unequivocal ACL tears. Subset 3 included patients with doubtful ACL who underwent arthroscopy. MR images were reviewed and sensitivity and specificity of vertically oriented LCL as an indirect sign of ACL tear were calculated.

The MRI results were as follows: subset 1, out of 282 patients, 270 had oblique LCL and 12 demonstrated vertical LCL; subset 2, out of 212 patients, 189 demonstrated vertical LCL and 23 revealed oblique LCL; subset 3, out of 62 patients, 28 patients with vertical orientation of LCL had a possible ACL tear. Patients with oblique LCL orientation (34) were reported as probably having normal ACL. On comparison with arthroscopy, in 28 patients who we reported as having possible ACL tears, there were 17 patients with torn ACL. The rest of the 11 patients revealed no ACL tears. In the group of 34 patients in whom we reported possible normal, arthroscopy-confirmed tear in 5 patients. Sensitivity and specificity of vertical LCL as an indirect sign of ACL tear was found to be 88% and the specificity 92.85%.

Vertically oriented LCL is a useful indirect MRI sign of ACL tear and aids in making a diagnosis, when ACL appearance is equivocal.