title: Quantitative magnetic resonance imaging (MRI) evaluation of cartilage repair after microfracture treatment for full-thickness cartilage defect models in rabbit knee joints: correlations with histological findings.
abstract: OBJECTIVE
  To evaluate repair tissue (RT) after microfracture treatment for full-thickness cartilage defect models using quantitative MRI and investigate the correlations between MRI and histological findings.
  
  
  METHODS
  The animal experiment was approved by the Animal Care and Use Committee of our college. Thirty-six full-thickness cartilage defect models in rabbit knee joints were assigned to the microfracture or joint debridement group (as control). Each group consisted of 3-week, 5-week, and 7-week subgroups. MR imaging, including a three-dimensional double-echo steady-state sequence (3D-DESS), and T2 mapping were performed at 3, 5, and 7 weeks postoperatively. The thickness and T2 indices of RT were calculated. After MRI scans at each time point, operation sites were removed to make hematoxylin-eosin (H&E)-stained sections. Histological results were evaluated using the modified O'Driscoll score system. Comparisons were made between the two groups with respect to the MRI and histological findings, and correlation analysis was performed within each group.
  
  
  RESULTS
  The thickness index and histological O'Driscoll score of RT in the two groups increased over time, while the T2 index decreased. The thickness index and histological O'Driscoll score of the microfracture group were higher than in the joint debridement group at each time point. The T2 index of the microfracture group was lower than in the joint debridement group at 3 weeks (P = 0.006), while it was higher than in the joint debridement group at 5 and 7 weeks (P = 0.025 and 0.025). The thickness index was positively correlated with the histological O'Driscoll score in both groups (microfracture: r s = 0.745, P < 0.001; joint debridement: r s = 0.680, P = 0.002). The T2 index was negatively correlated with the histological O'Driscoll score in both groups (microfracture: r s = -0.715, P = 0.002; joint debridement: r s = -0.826, P < 0.001).
  
  
  CONCLUSIONS
  Significant improvement over time after microfracture can be expected on the basis of the quantitative MRI finding and histological O'Driscoll score. MRI was correlated with the histological O'Driscoll score, which indicated that quantitative MRI 3D-DESS and T2 mapping could evaluate cartilage repair after microfracture as an effective noninvasive tool.
authors.affiliation: Department of Radiology, Huashan Hospital, Fudan University, 12 Wulumuqizhong Road, 200040, Shanghai, China.
authors.forename: Hongyue
authors.initials: H
authors.lastname: Tao
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.forename: Yinghui
authors.initials: Y
authors.lastname: Hua
authors.forename: Zhongqing
authors.initials: Z
authors.lastname: Chen
authors.forename: Xiaoyuan
authors.initials: X
authors.lastname: Feng
authors.forename: Shuang
authors.initials: S
authors.lastname: Chen
mesh_terms: D000818:Animals; D017102:Fracture Healing; D050724:Fractures, Cartilage / Q000473:pathology*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007718:Knee Injuries / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011817:Rabbits; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013223:Statistics as Topic