title: Graft maturation of autologous chondrocyte implantation: magnetic resonance investigation with T2 mapping.
abstract: BACKGROUND
  Autologous chondrocyte implantation (ACI) using tissue-engineered cartilage is a successful therapy for full-thickness cartilage lesions in the knee joint. However, in vivo graft maturation is still unclear.
  
  
  OBJECTIVE
  The aim of this prospective study was to analyze graft maturation after ACI in the knee using objective T2 mapping in correlation with the clinical outcomes within a 3-year postoperative course.
  
  
  METHODS
  Case series; Level of evidence, 4.
  
  
  METHODS
  A total of 13 patients with isolated cartilage defects of the knee were treated with Novocart 3D, a matrix-based ACI procedure in the knee joint. The patients had complete data from International Knee Documentation Committee (IKDC) scores and MRI examinations for 6 to 36 months postoperatively. All cartilage defects were arthroscopically classified as Outerbridge grades III and IV. The mean area of the cartilage defect was 5.6 cm(2). Postoperative clinical and MRI examinations were conducted at 6, 12, 24, and 36 months after surgery. The modified magnetic resonance observation of cartilage repair tissue (MOCART) score was used to evaluate the quality and integration of the Novocart 3D implants on MRI. The T2 relaxation time values of the ACI graft and healthy native cartilage areas were determined to assess graft maturation using T2 mapping.
  
  
  RESULTS
  The T2 relaxation times of the ACI graft showed significant improvement, with decreasing values from 41.6 milliseconds at 6-month follow-up to 32.4 and 30.9 milliseconds after 24 and 36 months, respectively. These values were similar to the T2 relaxation times of the native surrounding cartilage. There was no correlation between the clinical outcomes (IKDC score) and T2 relaxation time values.
  
  
  CONCLUSIONS
  The T2 relaxation time in the repaired tissue showed similar values compared with normal hyaline cartilage. Graft maturation after ACI in the knee joint needs at least 1 year, with ongoing adjustment of the T2 relaxation time values compared with native surrounding cartilage. A correlation between increasing ACI graft maturation and clinical outcomes (IKDC score) could not be found with the data available.
authors.affiliation: Department of Orthopaedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich, Grosshadern Campus, Munich, Germany.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Niethammer
authors.affiliation: Department of Orthopaedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich, Grosshadern Campus, Munich, Germany.
authors.forename: Elem
authors.initials: E
authors.lastname: Safi
authors.affiliation: Department of Orthopaedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich, Grosshadern Campus, Munich, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Ficklscherer
authors.affiliation: Institute of Clinical Radiology, Ludwig Maximilians University Munich, Campus Grosshadern, Munich, Germany.
authors.forename: Annie
authors.initials: A
authors.lastname: Horng
authors.affiliation: Department of Orthopaedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich, Grosshadern Campus, Munich, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Feist
authors.affiliation: Department of Orthopaedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich, Grosshadern Campus, Munich, Germany.
authors.forename: Isa
authors.initials: I
authors.lastname: Feist-Pagenstert
authors.affiliation: Department of Orthopaedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich, Grosshadern Campus, Munich, Germany.
authors.forename: Volkmar
authors.initials: V
authors.lastname: Jansson
authors.affiliation: Department of Orthopaedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich, Grosshadern Campus, Munich, Germany.
authors.forename: Matthias F
authors.initials: MF
authors.lastname: Pietschmann
authors.affiliation: Department of Orthopaedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich, Grosshadern Campus, Munich, Germany peter.mueller@med.uni-muenchen.de.
authors.forename: Peter E
authors.initials: PE
authors.lastname: Müller
mesh_terms: D000293:Adolescent; D000328:Adult; D001182:Arthroscopy; D002358:Cartilage, Articular / Q000293:injuries* / Q000601:surgery; D019902:Chondrocytes / Q000637:transplantation*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007719:Knee Joint / Q000601:surgery*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000379:methods*; D011446:Prospective Studies; D023822:Tissue Engineering; D014182:Transplantation, Autologous; D016896:Treatment Outcome
keywords: ACI; MRI; T2 relaxation time; autologous chondrocyte implantation; cartilage