title: Longitudinal split of the posterior cruciate ligament: description of a new MR finding and evaluation of its potential clinical significance.
abstract: OBJECTIVE
  To evaluate the clinical significance of the intra-substance longitudinal split of the posterior cruciate ligament (LS-PCL) and to evaluate its potential clinical significance on MRI.
  
  
  METHODS
  The databases of two centres were searched for LS-PCL, 6917 knee magnetic resonance imaging (MRI) examinations undertaken were retrospectively reviewed. LS-PCL was defined as increased signal intensity in a PCL in the longitudinal direction, but with an intact ligament outer surface on MRI. Twelve patients were enrolled in this study. Available arthroscopic results, degree of posterior knee instability, and changes in MRI findings, or the degree of instability during follow-up (FU), were reviewed from the patients medical records and via their MRI images. MRI images were reviewed by two musculoskeletal radiologists in consensus for presence and location of LS-PCL and any combined injuries: menisci lesions, ligament injuries, and bone marrow changes.
  
  
  RESULTS
  Seven of 12 patients (58.3%) had morphological or functional evidence of PCL injury or insufficiency according to the change of posterior instability on FU stress testing (n=3), insufficiency during arthroscopy (n=2), or decreased extent and altered shape of the PCL split on the FU MRI (n=3). One patient revealed both change of posterior instability on FU stress testing and insufficiency during arthroscopy. Combined injuries were revealed in seven patients. Five patients had isolated LS-PCL: two patients underwent arthroscopic PCL reconstructions; and another three patients revealed knee instability on stress testing.
  
  
  CONCLUSIONS
  Although LS-PCL has not been described before, it can be a type of partial tear of the PCL, which causes PCL insufficiency.
authors.affiliation: Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.
authors.forename: J H
authors.initials: JH
authors.lastname: Cha
authors.forename: H W
authors.initials: HW
authors.lastname: Chung
authors.forename: J W
authors.initials: JW
authors.lastname: Kwon
authors.forename: B K
authors.initials: BK
authors.lastname: Choi
authors.forename: S H
authors.initials: SH
authors.lastname: Lee
authors.forename: M J
authors.initials: MJ
authors.lastname: Shin
mesh_terms: D000293:Adolescent; D000328:Adult; D001182:Arthroscopy / Q000379:methods; D016208:Databases, Factual; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D007718:Knee Injuries / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D016119:Posterior Cruciate Ligament / Q000293:injuries* / Q000502:physiology; D012189:Retrospective Studies; D055815:Young Adult