USING MR-IMAGING TO DIAGNOSE PARTIAL TEARS OF THE ANTERIOR CRUCIATE LIGAMENT - VALUE OF AXIAL IMAGES

OBJECTIVE. The purpose of this study was to determine the usefulness o f axial MR imaging for diagnosing partial anterior cruciate ligament ( ACL) tears and to determine if patients could be categorized as having stable or unstable partial ACL tears on the basis of criteria of axia l MR imaging. MATERIALS AND METHODS, We reviewed 238 patients who, ove r a 2-year period, underwent both MR imaging of the knee and arthrosco pic evaluation of the ACL. According to arthroscopic Examination, thes e patients had 143 normal ACLs, 67 complete ACL tears, and 28 partial tears. The 28 partial tears included 20 stable rears (no ACL deficienc y) and eight unstable partial tears having ACL deficiency or requiring ACL reconstructive surgery, The axial MR im ages were retrospectively reviewed by two interpreters who were unaware of the arthroscopic fin dings, and decisions were reached by consensus. The ACL was classified according to its axial configuration and continuity. RESULTS. By axia l MR imaging criteria, we found 109 elliptical ACLs, 45 attenuated ACL s, three ACLs with increased intrasubstance signal intensity, six isol ated ACL bundle signs, 19 ACLs that could not be visualized, and 56 cl oudlike mass signs, Arthroscopically normal ACLs and stable partial te ars were difficult to distinguish reliably on axial MR images, Unstabl e partial ACL tears could not be distinguished from complete ACL tears . However, using axial MR imaging, our observers were able to segregat e stable ACLs (normal ligaments and stable partial tears) from unstabl e ACLs (unstable partial tears and complete tears) with 100% sensitivi ty and 96% specificity. CONCLUSION, Axial MR imaging of the ACL may pr ovide important diagnostic information for patients; who have ACL inju ry. On axial MR images, stable ACLs were elliptical, attenuated, or sh owed as areas of increased intrasubstance signal intensity, At arthros copy, attenuated ACLs represented normal ACLs (76%) and stable partial tears (24%). On axial MR images, the configurations that indicated un stable ligaments were isolated ACL bundle, nonvisualized ACL, and clou dlike mass.