title: Using three-dimensional isotropic SPACE MRI to detect posterolateral corner injury of the knee.
abstract: BACKGROUND
  Reliable magnetic resonance imaging (MRI) diagnosis is important in cases of posterolateral corner (PLC) injury due to the limitations of physical examination in patients with multi-ligament injury.
  
  
  OBJECTIVE
  To document the appearance of PLC of the knee on three-dimensional (3D) isotropic MR images, and to determine the significance of MRI findings in patients with confirmed posterolateral rotatory instability.
  
  
  METHODS
  Twenty-five patients that underwent surgery for posterolateral instability, and 25 individuals with normal MRI constituted the study cohort. The PLC appearances (popliteofibular, fabellofibular, arcuate ligaments, popliteomeniscal fascicle) were analyzed using 3D isotropic proton density sequence and routine two-dimensional (2D) MRI. In addition, the "fibular cap" sign was evaluated. Statistical analysis was performed using the Chi-square and McNemar's tests.
  
  
  RESULTS
  Thickening of popliteofibular, fabellofibular, arcuate ligaments, and popliteomeniscal fascicle was significantly more frequent in the PLC injury group than in the control group (P < 0.05). The sensitivity and specificity of 3D MRI for popliteofibular, fabellofibular, arcuate ligaments, and popliteomeniscal fascicle injury were 63/92%, 54/100%, 46/100%, and 58/92%, respectively. On comparing 3D and 2D images with respect to injury detectability (grade 3 or 4), both modalities visualized injuries, but 3D detected grade 3 or grade 1 rather than grade 4 or 0, respectively. The fibular cap sign was observed significantly more frequently in PLC group, with 58% sensitivity and 100% specificity, and was better observed by 3D than 2D (P < 0.05).
  
  
  CONCLUSIONS
  3D MRI is a valid modality for detecting PLC abnormalities as it visualizes pathologies in each component and exhibits the positive fibular cap sign.
authors.affiliation: Department of Radiology, Gachon University, Incheon, Republic of Korea.
authors.forename: Su Joa
authors.initials: SJ
authors.lastname: Ahn
authors.affiliation: Department of Radiology, Gachon University, Incheon, Republic of Korea.
authors.forename: Yu Mi
authors.initials: YM
authors.lastname: Jeong
authors.affiliation: Department of Orthopedics, Gachon University, Incheon, Republic of Korea.
authors.forename: Beom Goo
authors.initials: BG
authors.lastname: Lee
authors.affiliation: Department of Orthopedics, Gachon University, Incheon, Republic of Korea.
authors.forename: Jae Ang
authors.initials: JA
authors.lastname: Sim
authors.affiliation: Department of Radiology, Gachon University, Incheon, Republic of Korea.
authors.forename: Hye-Young
authors.initials: HY
authors.lastname: Choi
authors.affiliation: Department of Radiology, Gachon University, Incheon, Republic of Korea.
authors.forename: Jeong Ho
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Radiology, Gachon University, Incheon, Republic of Korea leesw1@gilhospital.com.
authors.forename: Sheen-Woo
authors.initials: SW
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D007718:Knee Injuries / Q000000981:diagnostic imaging* / Q000601:surgery; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome
keywords: Posterolateral corner; knee; magnetic resonance imaging (MRI); three-dimensional isotropic imaging