title: Intra- and interrater reliability of three different MRI grading and classification systems after acute hamstring injuries.
abstract: OBJECTIVE
  To assess and compare the intra- and interrater reliability of three different MRI grading and classification systems after acute hamstring injury.
  
  
  METHODS
  Male athletes (n=40) with clinical diagnosis of acute hamstring injury and MRI ≤5days were selected from a prospective cohort. Two radiologists independently evaluated the MRIs using standardised scoring form including the modified Peetrons grading system, the Chan acute muscle strain injury classification and the British Athletics Muscle Injury Classification. Intra-and interrater reliability was assessed with linear weighted kappa (κ) or unweighted Cohen's κ and percentage agreement was calculated.
  
  
  RESULTS
  We observed 'substantial' to 'almost perfect' intra- (κ range 0.65-1.00) and interrater reliability (κ range 0.77-1.00) with percentage agreement 83-100% and 88-100%, respectively, for severity gradings, overall anatomical sites and overall classifications for the three MRI systems. We observed substantial variability (κ range -0.05 to 1.00) for subcategories within the Chan classification and the British Athletics Muscle Injury Classification, however, the prevalence of positive scorings was low for some subcategories.
  
  
  CONCLUSIONS
  The modified Peetrons grading system, overall Chan classification and overall British Athletics Muscle Injury Classification demonstrated 'substantial' to 'almost perfect' intra- and interrater reliability when scored by experienced radiologists. The intra- and interrater reliability for the anatomical subcategories within the classifications remains unclear.
authors.affiliation: Aspetar, Orthopaedic and Sports Medicine Hospital, Doha, Qatar; Oslo Sports Trauma Research Center, Department of Sports Medicine, Norwegian School of Sport Sciences, Oslo, Norway. Electronic address: arnlaug.wangensteen@nih.no.
authors.forename: Arnlaug
authors.initials: A
authors.lastname: Wangensteen
authors.affiliation: Aspetar, Orthopaedic and Sports Medicine Hospital, Doha, Qatar; Amsterdam Center for Evidence Sports Medicine, Academic Medical Center, The Netherlands; The Sports Physician Group, OLVG, Amsterdam, The Netherlands. Electronic address: johannes.tol@aspetar.com.
authors.forename: Johannes L
authors.initials: JL
authors.lastname: Tol
authors.affiliation: Quantitative Imaging Center, Department of Radiology, Boston University School of Medicine, Boston, MA, USA; Department of Radiology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Frank W
authors.initials: FW
authors.lastname: Roemer
authors.affiliation: Aspetar, Orthopaedic and Sports Medicine Hospital, Doha, Qatar; Oslo Sports Trauma Research Center, Department of Sports Medicine, Norwegian School of Sport Sciences, Oslo, Norway.
authors.forename: Roald
authors.initials: R
authors.lastname: Bahr
authors.affiliation: Aspetar, Orthopaedic and Sports Medicine Hospital, Doha, Qatar.
authors.forename: H Paul
authors.initials: HP
authors.lastname: Dijkstra
authors.affiliation: Quantitative Imaging Center, Department of Radiology, Boston University School of Medicine, Boston, MA, USA; Department of Radiology, Saint-Antoine Hospital, University Paris VI, Paris, France.
authors.forename: Michel D
authors.initials: MD
authors.lastname: Crema
authors.affiliation: Aspetar, Orthopaedic and Sports Medicine Hospital, Doha, Qatar.
authors.forename: Abdulaziz
authors.initials: A
authors.lastname: Farooq
authors.affiliation: Quantitative Imaging Center, Department of Radiology, Boston University School of Medicine, Boston, MA, USA.
authors.forename: Ali
authors.initials: A
authors.lastname: Guermazi
mesh_terms: D000293:Adolescent; D000328:Adult; D001265:Athletic Injuries / Q000145:classification / Q000473:pathology*; D000070633:Hamstring Muscles / Q000293:injuries* / Q000473:pathology; D000070632:Hamstring Tendons / Q000293:injuries* / Q000473:pathology; D006801:Humans; D007869:Leg Injuries / Q000145:classification / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011446:Prospective Studies; D015203:Reproducibility of Results; D012421:Rupture / Q000145:classification / Q000473:pathology; D017695:Soft Tissue Injuries / Q000145:classification / Q000473:pathology; D055815:Young Adult
keywords: Classification; Hamstring injury; MRI; Magnetic resonance imaging; Radiological grading