Microfracture combined with osteochondral paste implantation was more effective than microfracture alone for full-thickness cartilage repair

The aim of this study was to evaluate whether the microfracture combined with osteochondral paste implantation could promote the quality of the regenerated tissue in the knee joints of rabbits. Sixty-six New Zealand white rabbits were used. Bilateral knee joints from the same rabbit were randomly divided into experimental group and microfracture group. An articular cartilage defect was established in the femoral trochlear groove. In the experimental group, the defect was microfractured and covered with osteochondral paste harvested from the intercondylar notch. The regenerated tissues were harvested for gross morphology, histology, biochemistry and gene expression analysis at 4, 8 and 12 weeks postoperatively. The regenerated tissue had a slowly mature process in both groups. At 12 weeks, the regenerated tissue in the experimental group appeared much more thicker and white with higher percentages of defect filling macroscopically. In histology, the experimental group found a majority of hyaline-like regenerate tissue with intense Safranin-O and collagen type II staining, while fibrocartilage-like tissue was mostly seen in the microfracture group with poor Safranin-O and collagen type II staining. The experimental group had higher Wakitani scores and narrower acellular zones than those in the microfracture group (P < 0.05). For biochemical analysis, both the GAG content and the DNA-normalized GAG content saw a time-dependent increase with a much higher value found in the experimental group at 8 and 12 weeks (P < 0.05). On the contrary, the total DNA content decreased with time in both groups, and the difference between the two groups was only found at 4 and 8 weeks (P < 0.05). For gene expression analysis, the experimental group had much higher expression levels than the microfracture group as for collagen type II and aggrecan, but not for collagen type I. Microfracture combined with paste implantation can result in improved quality of the reparative tissue and may have a positive effect on the integration to the surrounding cartilage in the rabbit model. The technique offers a promising treatment option for cartilage defects and improves the regeneration of articular cartilage for patients with painful chondral lesions.