Opening Lecture: Repair of Human Articular Cartilage: Where Are We Now?

There are many challenges in joint cartilage repair, of which most have not yet found a solution.

The theoretical challenge is to produce a tissue consisting mainly of collagen 2, organized in domes working as shelter for large, water binding and electrically negative molecules (e.g. GAGs) that secure the osmotic pressure in the tissue and it’s load absorbing properties. This tissue should be occupied by chondrocytes, renewing collagens and producing GAGs etc. The clinical challenge is to eliminate pain caused by the cartilage damage and the possible long-term consequence of larger cartilage defects: osteoarthritis.

In humans, microfracture has been a popular choice to treat defects since 1959. Microfracture forms a disorganized tissue mainly of collagen 1 and with no particular high content of GAGs etc. The load absorptive properties of this tissue is inferior, but clinically 80 % of patients become much better, and the surgery is easy to perform.

Mosaic plasty, where a cylinder of bone topped with hyaline cartilage is moved from one part of a joint (where it is less needed) to the cartilage defect creates a surface of hyaline cartilage, but there are donor site problems, in particular if the defect is large. Artificial plugs, mimicking the structure of bone and cartilage have been tried out (MaioRegen and Trufit) – the idea is, that cells will invade the construct and gradually form bone in the bottom and cartilage at the top. Clinical results were varying but in general positive, but the method is now left, as CT and MRI scans showed very little tissue in the defects. Frozen mosaic cylinders from human donors have good short term results but all fail with time. Living osteochondral grafts from human donors (mega-oats) can be used to repair very large defects and results are positive, also long-term. Allografts are only available in some countries, though.  [...]