Aim of the study: The purpose of the study was to evaluate whether the implantation of a mixed type I-type II collagen scaffold associated with subchondral perforations, would improve the reparative outcomes of sub-chondral perforations by themselves, in rabbit articular cartilage lesions, over a period of 6 months.

Materials and Methods: Ten NZW rabbits were operated bilaterally on knees. Two chondral defects of 5 mm diameter were produced in each condyle in a standardized manner, without penetrating the subchondral bone. At random, one of these lesions was treated with sub-chondral perforations, and the other with subchondral perforations and apposition of the type I-type II collagen scaffold. The membrane was secured with a transosseus stitch. The overall number of lesions was forty; twenty treated defects and twenty control defects. Rabbits were killed after six months since surgery. Then histological and histomorphometrical evaluation were performed. The O’Driscoll score was used to evaluate the quality of reparative tissue.

Results: The amount of defect fill resulted significantly greater in treated lesions rather than in control lesions. The defect fill increased from 60% to 85% of the total area of the lesion. From a histological point of view, the quality of reparative tissue improved with the addition of the scaffold, as resulted by an increase in O’Driscoll Score. Particularly, hyaline-like tissue was detected in 75% of treated lesions, rather than in 15% of control lesions.

Conclusions: The addition of a mixed type I-type II collagen membrane enhances reparative effects given by subchondral perforations. Both the histological and structural quality of the reparative tissue, both the percentage area of defect fill result to be improved by this kind of membrane.