title: Rotational Knee Laxity in Anterior Cruciate Ligament Deficiency: An Additional Secondary Sign on MRI.
abstract: OBJECTIVE
  The objective of this study was to evaluate the accuracy of tibial rotation measurement as a secondary sign for diagnosing anterior cruciate ligament (ACL) tears with the use of MRI.
  
  
  METHODS
  A total of 893 MRI studies were retrospectively reviewed, and 239 patients were identified as having either an intact ACL (group 1; n = 182), an arthroscopically confirmed acutely torn ACL (group 2; n = 22), or a chronically torn ACL (group 3; n = 35). Tibial rotation was estimated by measuring the femorotibial angle (FTA).
  
  
  RESULTS
  The mean (± SD) FTA was significantly higher in group 2 (10.7° ± 4.8°) and group 3 (11° ± 5.5°) than in group 1 (3.2° ± 3.3°) (p < 0.001, for all cases). An FTA of 4.9° was the optimal threshold (sensitivity, 93%; specificity, 80%) for separating completely torn ACLs from intact ACLs. An FTA ranging from 4.9° to 5.5° (sensitivity, 95%; specificity, 80%) indicated a complete acute ACL tear, whereas an FTA of 5.6° or greater (sensitivity, 91.4%; specificity, 83.5%) suggested a complete chronic ACL tear.
  
  
  CONCLUSIONS
  An increased FTA indicates alteration in the femorotibial anatomic relationship and could be of value in assessing ACL tears in patients with equivocal signs on MRI.
authors.affiliation: 1 Department of Medical Imaging, University Hospital of Heraklion, Heraklion, Crete 71110, Greece.|2 Radiology Section, School of Medicine, University of Crete, Heraklion, Crete, Greece.
authors.forename: Evangelia E
authors.initials: EE
authors.lastname: Vassalou
authors.affiliation: 1 Department of Medical Imaging, University Hospital of Heraklion, Heraklion, Crete 71110, Greece.|2 Radiology Section, School of Medicine, University of Crete, Heraklion, Crete, Greece.|3 Present address: Biological Systems Engineering Laboratory, Department of Chemical Engineering, Imperial College London, London, United Kingdom.
authors.forename: Michail E
authors.initials: ME
authors.lastname: Klontzas
authors.affiliation: 4 Department of Orthopaedic Surgery, University Hospital of Heraklion, Heraklion, Crete, Greece.
authors.forename: Georgios K
authors.initials: GK
authors.lastname: Kouvidis
authors.affiliation: 1 Department of Medical Imaging, University Hospital of Heraklion, Heraklion, Crete 71110, Greece.
authors.forename: Paraskevi I
authors.initials: PI
authors.lastname: Matalliotaki
authors.affiliation: 1 Department of Medical Imaging, University Hospital of Heraklion, Heraklion, Crete 71110, Greece.|2 Radiology Section, School of Medicine, University of Crete, Heraklion, Crete, Greece.
authors.forename: Apostolos H
authors.initials: AH
authors.lastname: Karantanas
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000070598:Anterior Cruciate Ligament Injuries; D001182:Arthroscopy; D002648:Child; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000175:diagnosis*; D007718:Knee Injuries / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013977:Tibia / Q000033:anatomy & histology
keywords: MRI; anterior cruciate ligament; anterior cruciate ligament tear; indirect diagnostic criteria; knee joint; laxity