title: MRI but not arthroscopy accurately diagnoses femoral MPFL injury in first-time patellar dislocations.
abstract: OBJECTIVE
  The purpose of this study was to investigate whether the femoral part of the medial patellofemoral ligament (MPFL) and its injury can be accurately assessed by standard knee arthroscopy in first-time patellar dislocations or whether preoperative MRI is required to determine injury location in patients where primary MPFL repair is attempted.
  
  
  METHODS
  Twelve patients with acute first-time dislocations and MRI-based injury of the femoral MPFL and ten patients with recurrent patellar dislocations underwent knee arthroscopy with the use of a 30-degree optic and standard antero-medial and antero-lateral portals. The femoral origin was marked with a cannula under lateral fluoroscopy. Arthroscopic findings of the location of the native femoral MPFL and its injury were compared to the results of MRI and mini-open exploration.
  
  
  RESULTS
  In acute cases, the average time from primary patellar dislocation to MRI evaluation was 3 days (1-9 days), and the average time from MRI to surgery was 8 days (3-20 days). The native femoral origin of the MPFL was not visible in any of the chronic cases during arthroscopy. In addition, in all acute cases, arthroscopy failed to directly visualize injury of the femoral MPFL (0 of 12), but mini-open exploration confirmed injury in 11 of 12 patients. This means that arthroscopy was less accurate than MRI for the diagnosis of femoral MPFL injury (P < 0.05).
  
  
  CONCLUSIONS
  The results of this study indicate the limitations of knee arthroscopy in identifying the femoral disruption of the MPFL, a crucial injury that occurs in patellar dislocations. Thus, if a primary MPFL repair is planned, determination of the site of repair should be based on the preoperative MRI.
  
  
  METHODS
  Diagnostic study of non-consecutive patients, Level III.
authors.affiliation: Department of Trauma Surgery, Plastic and Reconstructive Surgery, University Medicine, Robert-Koch-Str. 40, 37075, Göttingen, Germany. peter.balcarek@med.uni-goettingen.de
authors.forename: Peter
authors.initials: P
authors.lastname: Balcarek
authors.forename: Tim Alexander
authors.initials: TA
authors.lastname: Walde
authors.forename: Stephan
authors.initials: S
authors.lastname: Frosch
authors.forename: Jan Philipp
authors.initials: JP
authors.lastname: Schüttrumpf
authors.forename: Martin Michael
authors.initials: MM
authors.lastname: Wachowski
authors.forename: Klaus Michael
authors.initials: KM
authors.lastname: Stürmer
mesh_terms: D000293:Adolescent; D000328:Adult; D001182:Arthroscopy / Q000379:methods*; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000175:diagnosis* / Q000601:surgery; D007719:Knee Joint / Q000601:surgery; D008023:Ligaments, Articular / Q000293:injuries* / Q000601:surgery; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D031222:Patellar Dislocation / Q000175:diagnosis* / Q000601:surgery; D057071:Patellofemoral Joint / Q000293:injuries*; D055815:Young Adult
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