title: Accuracy of magnetic resonance imaging signal intensity ratio measurements in the evaluation of multifidus muscle injury and atrophy relative to that of histological examinations.
abstract: METHODS
  A matched-pairs animal study.
  
  
  OBJECTIVE
  To confirm the accuracy of magnetic resonance imaging (MRI) as a means of evaluating edema and fat degeneration of the multifidus muscle by comparing measurements made using MRI with those made using histological examination.
  
  
  BACKGROUND
  MRI is considered a reliable means of evaluating multifidus muscle edema and fat degeneration. However, it is not clear whether its results are always consistent with histological findings.
  
  
  METHODS
  Models of different degrees of multifidus injury were created at the L2-L3, L3-L4, and L4-L5 disc levels in 56 New Zealand white rabbits. These were divided into 4 groups and subjected to different processes: sham surgery, dissection and stripping of the multifidus, crushing of the muscle lasting 1 hour, and crushing of the muscle lasting 2 hours. Two rabbits per group were examined at each of the indicated points in time. Multifidus edema was assessed using fat-suppressed T2 signal intensity ratio of gross multifidus to psoas (T2R) on MRI bilaterally, wet weight and wet:dry weight ratio on the left side (edema-left), and visual edema score on the right side (edema-right). Muscle fat degeneration was detected bilaterally using the T1 signal intensity ratio of gross multifidus to psoas with MRI (T1R) and visual fat degeneration score (fat score) with histology.
  
  
  RESULTS
  Pearson correlation coefficient analyses showed significant correlations (P < 0.001) between left T2R and edema-left (r = 0.927), right T2R and edema-right (r = 0.868), and T1R and fat score (r = 0.804). A paired t test demonstrated no significant differences between MRI measurements and histological changes (P = 0.999, 1.000, and 0.998). Bland-Altman plots also depicted good agreement between MRI measurements and histological changes (limits of agreement: left multifidus edema, ± 0.75; right multifidus edema, ± 1.01; fat degeneration, ± 1.23).
  
  
  CONCLUSIONS
  The MRI technique is an accuracy means of evaluating multifidus muscle injury and atrophy.
authors.affiliation: *Department of Orthopaedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, China †Key Laboratory of Biotherapy of Zhejiang Province, Hangzhou, China ‡Department of Radiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, China; and §Department of Pathology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, China.
authors.forename: Hu
authors.initials: H
authors.lastname: Zhi-Jun
authors.forename: Xu
authors.initials: X
authors.lastname: Wen-Bin
authors.forename: Chen
authors.initials: C
authors.lastname: Shuai
authors.forename: Zhou
authors.initials: Z
authors.lastname: Zhi-Jie
authors.forename: Zhao
authors.initials: Z
authors.lastname: Feng-Dong
authors.forename: Yu
authors.initials: Y
authors.lastname: Xiao-Jing
authors.forename: Wang
authors.initials: W
authors.lastname: Ji-Ying
authors.forename: Han
authors.initials: H
authors.lastname: Li-Li
authors.forename: Jiang
authors.initials: J
authors.lastname: Feng
authors.forename: Fu
authors.initials: F
authors.lastname: Guo-Xiang
authors.forename: Wu
authors.initials: W
authors.lastname: Dan-Ju
authors.forename: Fan
authors.initials: F
authors.lastname: Shun-Wu
authors.forename: Fang
authors.initials: F
authors.lastname: Xiang-Qian
mesh_terms: D000818:Animals; D004487:Edema / Q000473:pathology*; D008159:Lumbar Vertebrae; D008279:Magnetic Resonance Imaging; D009133:Muscular Atrophy / Q000473:pathology*; D009135:Muscular Diseases / Q000473:pathology*; D064170:Paraspinal Muscles / Q000293:injuries* / Q000473:pathology; D011817:Rabbits