title: MRI appearance does not change in the first 7 days after acute hamstring injury-a prospective study.
abstract: BACKGROUND
  The optimal timing of MRI following acute hamstring injury is not known and is mainly based on expert opinions.
  
  
  OBJECTIVE
  To describe the day-to-day changes in the extent of oedema and investigate the optimal timing for detection of fibre disruption on MRI following acute hamstring injuries.
  
  
  METHODS
  Prospective, descriptive study.
  
  
  METHODS
  We performed standardised MRI (1.5T) ≤1 day after injury in male athletes with acute hamstring injury. If initial MRI revealed positive signs of injury (increased signal intensity on fluid sensitive sequences), consecutive MRIs were obtained daily throughout the subsequent week (ie, 7 times). The MRI parameters (day 1-7) were scored by a single radiologist using a standardised scoring form. The day-to-day changes in the extent of oedema (distance from tuber, craniocaudal length, mediolateral width and anteroposterior depth) and the presence and extent of fibre disruption (tear) were assessed with descriptive statistics and repeated measures using analysis of variance of log-transformed data. The overall main effect for time was reported with a significance level set at p<0.05.
  
  
  RESULTS
  13 out of 132 male athletes assessed for eligibility between January 2014 and December 2015 were included. 1 dropped out, while 12 (31 years, range 20-49) completed the study; 11 had 7 MRI scans each and one had 5 MRI scans performed. There were no significant day-to-day changes for any of the extent of oedema measures (p values ranging from 0.12 to 0.81). Fibre disruption (tear), present in 5 of the athletes, was detectable from day 1, with small and insignificant day-to-day changes (p values ranging from 0.45 to 0.95).
  
  
  CONCLUSIONS
  We observed insignificant day-to-day changes in the extent of oedema throughout the first week following acute hamstring injury. Fibre disruption (tear) was detectable from the first day after injury. These findings indicate that MRI can be performed on any day during the first week following an acute (hamstring) muscle injury.
authors.affiliation: Aspetar, Orthopaedic and Sports Medicine Hospital, Doha, Qatar.|Department of Sports Medicine, Oslo Sports Trauma Research Center, Norwegian School of Sport Sciences, Oslo, Norway.
authors.forename: Arnlaug
authors.initials: A
authors.lastname: Wangensteen
authors.affiliation: Aspetar, Orthopaedic and Sports Medicine Hospital, Doha, Qatar.|Department of Sports Medicine, Oslo Sports Trauma Research Center, 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: Robbart
authors.initials: R
authors.lastname: Van Linschoten
authors.affiliation: Aspetar, Orthopaedic and Sports Medicine Hospital, Doha, Qatar.
authors.forename: Emad
authors.initials: E
authors.lastname: Almusa
authors.affiliation: Aspetar, Orthopaedic and Sports Medicine Hospital, Doha, Qatar.
authors.forename: Rodney
authors.initials: R
authors.lastname: Whiteley
authors.affiliation: Aspetar, Orthopaedic and Sports Medicine Hospital, Doha, Qatar.|Faculty of Medicine and Health Sciences, Department Rehabilitation Science and Physiotherapy, Ghent University, Belgium.
authors.forename: Erik
authors.initials: E
authors.lastname: Witvrouw
authors.affiliation: Aspetar, Orthopaedic and Sports Medicine Hospital, Doha, Qatar.|Amsterdam Center for Evidence Based Medicine, Academic Medical Center, Amsterdam, The Netherlands.|Sports Medicine Department, OLVG, Amsterdam, The Netherlands.
authors.forename: Johannes L
authors.initials: JL
authors.lastname: Tol
mesh_terms: D000328:Adult; D001265:Athletic Injuries / Q000000981:diagnostic imaging*; D004487:Edema / Q000000981:diagnostic imaging; D006801:Humans; D007869:Leg Injuries / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging* / Q000293:injuries; D011446:Prospective Studies; D017695:Soft Tissue Injuries / Q000000981:diagnostic imaging*; D013848:Thigh / Q000000981:diagnostic imaging / Q000293:injuries; D013997:Time Factors; D055815:Young Adult
keywords: Hamstrings; MRI; Muscle