P99 WHAT IS IMPORTANT IN CARTILAGE REPAIR-MACROSCOPIC GRADING OR HISTOLOGY?

Aims To investigate (1) The relationship between macroscopic grading and durability of cartilage repair following collagen-covered autologous chondrocyte implantation (ACI-C) in the knee; (2) The influence of histology on durability of cartilage repair; (3) The relationship between macroscopic appearance and histology of repair tissue. Patients and methods The modified Cincinnati scores (MCRS) of eighty-six patients were evaluated prospectively at one year and at the latest follow-up (mean follow-up = 4.7yrs. Range = 4 to 7 years). Needle biopsies of their cartilage repair site were stained with Haematoxylin and Eosin and some with Safranin O and the neo-cartilage was graded as hyaline-like (n=32, 37.2%), mixed fibro-hyaline (n=19, 22%) and fibro-cartilagenous tissue (n=35, 40.7%). Macroscopic grading of the repair tissue using the international cartilage repair society grading system (ICRS) was available for fifty-six patients in the study cohort. Statistical analyses were performed to investigate the significance of histology and ICRS grading on MCRS at 1 year and at the latest follow-up. Results The MCRS of all three histology groups were comparable at one year evaluation (p=0.34). However, their clinical scores at the latest follow-up (mean = 4.7years) showed a significantly superior result for those with hyaline-like repair tissue when compared to those with mixed fibro-hyaline and fibro-cartilagenous repair (p=0.05). There was no correlation between the ICRS macroscopic grading and MCRS (clinical) grading either at one year (p=0.12) or at the latest follow-up (p=0.16). Also, the ICRS grading of the repair tissue did not correlate with its histological type (p=0.12). Conclusion We conclude that any form of cartilage repair gave a good clinical outcome at one year. At four years and beyond, hyaline-like repair tissue was associated with a more favourable clinical outcome. Macroscopic evaluation using the ICRS grading system does not reflect the clinical outcome or its durability or the histological type of repair tissue.