Autogenous osteochondral morselised grafts for full thickness osteochondral defects in the knee joints of pigs

The aim of this study is to firstly ascertain the survival of autogenously grafted morselised cartilage for full thickness osteochondral defects in knee joints of pigs. Secondly, it is to determine the quality of the grafted cartilage that survives and to score to it based on a recognised and tested system of indices and thirdly, to recognise, if any, the potential for reconstitution of the osteochondral junction. Two groups of five pigs were followed up for six and 12 weeks. Similar osteochondral defects were created in the medial condyles of both knees with the right medial femoral condyle defect filled with graft and the left used as control and filled with gel foam. At the end of the study period, an independent pathologist assessed the defects macroscopically and microscopically with an accepted and comparable histological scoring system. Macroscopically, there was better filling of the defect and restoration of bony contour in the grafted group compared to the control. Microscopically, at six weeks, filling of the defect, nature of predominant tissue, matrix staining and nature of cells all showed significantly better histological score than the control using the Mann-Whitney U test at the level of significance of p<0.05. At 12 weeks, in addition to the above, the reconstitution of osteochondral junction also showed a significantly better score. Comparing the test groups at six and 12 weeks, the reconstitution of the osteochondral junction was significantly better at 12 weeks. In conclusion, the autogenous osteochondral morselised graft persisted as mature hyaline cartilage with good histological score at six weeks with significantly better reconstitution of osteochondral junction occurring at 12 weeks. The use of morselised graft allows for the inclusion of bone graft which possibly allows for larger amounts of donor tissue and thus the possibility of treating larger defects. In the human model the donor site would be the non-weight bearing surfaces of the knee such as the intercondylar notch as described by Walgenbach A and Stone KR at the 1997 Annual Meeting of the American Academy of Orthopaedic Surgeons in San Francisco.