Clinical, radiological, and histological outcomes after the fibrin–matrix autologous chondrocyte implantation for chondral lesions of the knee in patients more than 50 years old: A prospective case series with minimum 2-year follow-up

Background: The purpose of this study was to evaluate clinical and radiological outcomes and to analyze the histological findings of repaired cartilage in patients more than 50 years old with underwent fibrin–matrix autologous chondrocyte implantation (ACI). Methods: From January 2013 to February 2014, a prospective study was conducted on 16 patients (16 knees) who underwent fibrin–matrix ACI for International Cartilage Repair Society grade 3 or 4 chondral lesions of the knee. The major lesion was in the medial femoral condyle in all patients. The mean age of the patients was 58.1 ± 6.2 (range 51–66) years, and the minimum follow-up period was 2 years. All patients had clinical and radiological evaluations at 3 months, 6 months, 1 year, and 2 years after surgery. Twelve patients had second-look arthroscopies at 1 year after surgery, and implanted chondral biopsies were performed in 11 of these 12 patients for histological analysis. Results: Functional disability assessment scales for the knee significantly improved after fibrin–matrix ACI ( p < 0.05). The visual analog scale score significantly decreased from 6.7 ± 1.2 to 2.0 ± 1.8 ( p < 0.001). The mean modified magnetic resonance observation of cartilage repair tissue score was 83.8 ± 17.3 at 1 year after surgery and 74.0 ± 19.2 at 2 years after surgery. Repair of the tissue with hyaline cartilage was confirmed histologically. Conclusions: Satisfactory clinical and radiological outcomes were obtained from gel-type fibrin–matrix ACI technique in older patients with a cartilage defect of the knee. Histological analysis confirmed that the new repaired tissue with hyaline cartilage filled the cartilage defect area. Therefore, fibrin–matrix ACI is believed to be an applicable treatment for older patients with chondral lesions of the knee. Level of evidence: Level IV.