title: Quantitative and qualitative MR-imaging assessment of vastus medialis muscle volume loss in asymptomatic patients after anterior cruciate ligament reconstruction.
abstract: BACKGROUND
  To quantitatively and qualitatively assess vastus medialis muscle atrophy in asymptomatic patients with anterior cruciate ligament reconstruction, using the nonoperated leg as control.
  
  
  METHODS
  Prospective Institutional Review Board approved study with written informed patient consent. Thirty-three asymptomatic patients (men, 21; women,12) with ACL-reconstruction underwent MR imaging of both legs (axial T1-weighted spin-echo and 3D spoiled dual gradient-echo sequences). Muscle volume and average fat-signal fraction (FSF) of the vastus medialis muscles were measured. Additionally, Goutallier classification was used to classify fatty muscle degeneration. Significant side differences were evaluated using the Wilcoxon test and, between volumes and FSF, using student t-tests with P-value < 0.05 and < 0.025, respectively.
  
  
  RESULTS
  The muscle volume was significantly smaller in the operated (mean ± SD, 430.6 ± 119.6 cm(3) ; range, 197.3 to 641.7 cm(3) ) than in the nonoperated leg (479.5 ± 124.8 cm(3) ; 261.4 to 658.9 cm(3) ) (P < 0.001). Corresponding FSF was 6.3 ± 1.5% (3.9 to 9.2%) and 5.8 ± 0.9% (4.0 to 7.4%), respectively, with a nonsignificant (P > 0.025) difference. The relative muscle-volume and FSF differences were -10.1 ± 8.6% (7.1 to -30.1%) and 10.9 ± 29.4% (39.7 to 40.1%). The qualitative assessment revealed no significant differences (P > 0.1).
  
  
  CONCLUSIONS
  A significant muscle volume loss of the vastus medialis muscle does exist in asymptomatic patients with ACL-reconstruction, but without fatty degeneration.
authors.affiliation: Department of Radiology, University Hospital Zurich, Zurich, Switzerland.|Department of Radiology, University Hospital Udine, P.le S. Maria della Misericordia Udine, Italy.
authors.forename: Magda
authors.initials: M
authors.lastname: Marcon
authors.affiliation: Department of Traumatology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Ciritsis
authors.affiliation: Department of Traumatology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Laux
authors.affiliation: Department of Radiology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Nanz
authors.affiliation: Department of Radiology, University Hospital Zurich, Zurich, Switzerland.|Division of Medical Imaging and Technology, Department of Clinical Science, Intervention and Technology (CLINTEC), Karolinska Institute, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Fischer
authors.affiliation: Department of Radiology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Gustav
authors.initials: G
authors.lastname: Andreisek
authors.affiliation: Department of Radiology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Erika J
authors.initials: EJ
authors.lastname: Ulbrich
mesh_terms: D000328:Adult; D059549:Anterior Cruciate Ligament Reconstruction / Q000009:adverse effects*; D058070:Asymptomatic Diseases; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D007866:Leg; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009133:Muscular Atrophy / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology*; D009929:Organ Size; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D055815:Young Adult
keywords: anterior cruciate ligament reconstruction; fat signal fraction; muscle weakness; muscular atrophy; vastus medialis muscle