THE DEEP LATERAL FEMORAL NOTCH - AN INDIRECT SIGN OF A TORN ANTERIOR CRUCIATE LIGAMENT

Magnetic resonance (MR) imaging has shown that tears of the anterior cruciate ligament (ACL) are frequently accompanied by meniscal and osseous injuries. Abnormalities of the cartilage overlying the lateral femoral condylopatellar sulcus (notch) also have been noted during arthrotomy of ACL-deficient knees. In this study, the appearance of this sulcus on MR images and the depth of the sulcus on conventional radiographs are compared in patients with normal and tom ACLs to determine whether a deep sulcus is a useful indirect sign of a tom ACL. In 62 patients with clinically and/or arthroscopically confirmed normal ACLs, the mean depth of the lateral femoral sulcus was 0.45 mm (range, 0.0-1.2 mm) compared with 0.89 mm (range, 0.0-5.0 mm) in 41 patients with clinically and/or arthroscopically confirmed ACL tears (significant at the 5% level). No patient with a normal ACL had a sulcus greater than 1.2 mm in depth. A sulcus deeper than 1.5 mm is equivalent to 3 standard deviations above the mean and was a reliable indirect sign of a torn ACL.