MRI signs of anterior cruciate ligament tears

Abstract

Objective To investigate the direct and indirect MRI manifestations of anterior cruciate ligament(ACL)tears and discuss its mechanism and diagnostic value.Methods The study involved 40 patients with ACL tears including 37 males and three females at age range of 16-49 years(mean age of 33 years).Arthroscopy and operation confirmed 28 patients at acute phase of ACL tears,12 at chronic phase of ACL tears,35 with complete ACL tears and five with partial ACL tears.All patients were examined on 1.5T Siemens MRI scanner,with SE,TSE or Medic sequence in multiple directions.The direct and indirect MRI manifestations of ACL tears were retrospectively and statistically analyzed by employing three experienced doctors.Results Among 28 patients with acute tears,the direct MRI signs included signal interruption or non-consecutive(86%),uneven signal(64%)and swelling and thickening ligament(36%).While in 12 patients with chronic teats,the MRI signs manifested swelling ligament(92%),signal interruption or non-consecutive(75%)and uneven signal(58%).The sign of thickening ligament was mainly seen at chronic phase of ACL tears(P ＜0.01).Of 35 patients with complete ACL tears,80% occurred in the middle part of ACL,with low incidence of upper and lower parts.All five patients with partial ACL tears occurred in the anteriomedialis bundle.The indirect MRI signs of ACL tears included 7-shaped deformity of posterior cruciate ligament(PCL)(34 patients,85%),meniscus exposure(26 patients)including 16 with lateral meniscus exposure(62%),bone injury(15 patients)including segond fracture(8 patients,53%),widened joint space(9 patients)including 78% at chronic phase,and tibia antelocation(23 patients,57%).Among 40 patients,37 patients were diagnosed correctly preoperatively,with accuracy rate of 92%.While three patients with partial ACL tears were missed diagnosis preoperatively,with inaccuracy rate of 8%.Conclusion ACL tear is relatively easy to identify preoperatively according to direct and indirect MRI signs in combination with trauma history. Key words: Anterior cruciate ligament; Magnetic resonance imaging; Signs