title: [MRI monitoring of autologous hyaline cartilage grafts in the knee joint: a follow-up study over 12 months].
abstract: OBJECTIVE
  To evaluate the suitability of different MR sequences for monitoring the stage of maturation of hyaline cartilage grafts in the knee joint and the early detection of complications like hypertrophy. In addition, it was analyzed whether indirect MR arthrography can indicate debonding of the graft.
  
  
  METHODS
  MRI examinations were performed in 19 patients, aged 17 - 48 years, with autologous transplantation of a hyaline cartilage tissue graft after knee trauma. Examination dates were prior to transplantation to localize the defect, and 6 weeks, 3, 6 and 12 months after transplantation to control morphology and maturation of the autologous graft. Standard T2- and proton-density-weighted turbo spin echo (TSE) sequences and T1-weighted spin echo (SE) sequences were used, as well as gradient echo (GRE) sequences with and without magnetization transfer (MT) prepulses. In some cases, indirect MR arthrography was performed.
  
  
  RESULTS
  Cartilage defect and the hyaline cartilage graft could be detected in all 19 patients. Hypertrophy of the graft could be found early in 3 patients and debonding in 1 patient. For depicting the graft a short time after surgery, T2-weighted TSE-sequences showed the best results. Six and 12 months after transplantation, spoiled 3D-GRE-sequences like FLASH3D (fast low angle shot) showed reduced artifacts due to magnetic residues from the surgery. Difference images from GRE-sequences with and without MT pulse provided high contrast between cartilage and surrounding tissue. The quantification of the MT effect showed an assimilation of the graft to the original cartilage within 12 months. Indirect MR arthrography showed subchondral contrast medium even 12 months after transplantation in 3 patients.
  
  
  CONCLUSIONS
  MRI allows a reliable depiction of the hyaline graft and provides very early detection of complications like hypertrophy. The MT effect seems to be correlated with maturation of the graft and allows selective depiction of normal cartilage and engrafted cartilage.
authors.affiliation: Abteilung für radiologische Diagnostik/Sektion für experimentelle Radiologie, Eberhard-Karls-Universität Tübingen. Christian.Mueller@med.uni-tuebingen.de
authors.forename: C
authors.initials: C
authors.lastname: Müller-Horvat
authors.forename: F
authors.initials: F
authors.lastname: Schick
authors.forename: C D
authors.initials: CD
authors.lastname: Claussen
authors.forename: E
authors.initials: E
authors.lastname: Grönewäller
mesh_terms: D000293:Adolescent; D000328:Adult; D001175:Arthrography / Q000379:methods*; D016477:Artifacts; D002356:Cartilage / Q000637:transplantation*; D019902:Chondrocytes / Q000637:transplantation*; D005500:Follow-Up Studies; D006801:Humans; D007718:Knee Injuries / Q000601:surgery*; D007719:Knee Joint / Q000601:surgery*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D013997:Time Factors; D014182:Transplantation, Autologous