title: Matrix-induced autologous chondrocyte implantation (MACI) in the knee.
abstract: OBJECTIVE
  Matrix-induced autologous chondrocyte implantation (MACI) has been in use for chondral defect repair since 2000, but to date, only little is known about its histological outcomes in the repair of knee cartilage defects. This prospective multicentre study aims to evaluate (1) the quality of the repair tissue obtained from biopsies taken during second-look arthroscopy and (2) the relationship between the histological outcome, the macroscopic appearance of the repair and the patients' functional status.
  
  
  METHODS
  Thirty-three second-look core biopsies from 30 patients treated with MACI were analysed. At the time of biopsy, the surgeon reported the reason for the second-look arthroscopy, the quality of the repair tissue and the patient's functional status on a standardised form. Biopsies together with patient data were sent to our centre to undergo blind histological evaluation and data analysis.
  
  
  RESULTS
  The median overall ICRS II histological score of the examined population was 57 (1st-3rd quartile 41-75). According to the ICRS cartilage repair assessment (CRA) arthroscopic evaluation, 10 biopsies (30%) were classified as normal, 17 (51%) as nearly normal, 4 (12%) as abnormal and 2 (6%) as severely abnormal. The histological outcome was not significantly related either to the macroscopic appearance of the lesion or to the patient's functional status at the time of biopsy.
  
  
  CONCLUSIONS
  In the examined population, the macroscopic appearance of the repair tissue gave an overly favourable impression in comparison with the real histological composition of the tissue, which was possibly still maturing in many cases. The healing process after MACI needs to be better understood through a larger histological study, and a longer follow-up is needed to better clarify the relationship between histology and long-term functional status.
  
  
  METHODS
  IV.
authors.affiliation: Department of Orthopedics, Polytechnic University of Marche, Via Tronto 10/A, 60020, Ancona, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Enea
authors.forename: Stefano
authors.initials: S
authors.lastname: Cecconi
authors.forename: Alberto
authors.initials: A
authors.lastname: Busilacchi
authors.forename: Sandra
authors.initials: S
authors.lastname: Manzotti
authors.forename: Rosaria
authors.initials: R
authors.lastname: Gesuita
authors.forename: Antonio
authors.initials: A
authors.lastname: Gigante
mesh_terms: D000328:Adult; D001706:Biopsy; D002358:Cartilage, Articular / Q000473:pathology / Q000601:surgery*; D019902:Chondrocytes / Q000473:pathology / Q000637:transplantation*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007717:Knee / Q000473:pathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D024162:Second-Look Surgery; D014182:Transplantation, Autologous / Q000379:methods*; D016896:Treatment Outcome; D055815:Young Adult