Articular cartilage is a thin, smooth, soft and elastic membrane that covers the articular surfaces of bones and allows smooth and minimal friction movement of the articular surfaces.
Its main function is the distribution of loads and the reduction of pressures on the subchondral bone (the bone below the cartilage).
It consists of water, collagen, proteoglycans, proteins and chondrocytes. This unique composition ensures special mechanical properties: it can be deformed during loading and, after removal, regain its original shape and return to its original thickness.
“Cartilage is not penetrated by nerves or blood vessels and is nourished by diffusion from synovial fluid. This is produced by the synovial membrane and its amount in a normal joint is minimal.
The consequence of this is that articular cartilage has a limited capacity for self-healing and self-repair, with the result that when it is injured or affected by a disease (rheumatoid arthritis, septic arthritis, osteonecrosis, etc.), it leads to progressive destruction.
If the initial damage to the cartilage is not diagnosed and treated in time, then the chondropathy that is created initially leads to osteoarthritis”, explains Mr. Dimitrios P. Dobris, Orthopedic Surgeon, Orthopedic Supervisor at the Metropolitan Hospital, Doctor of the University of Athens.
Symptomatic lesions are usually 2-4 cm in size. These affect the normal function of the joint and cause pain (pain), hydroarthrosis (fluid accumulation), stiffness, while some may block the joint.
The treatment of cartilage deficits must be individualized due to the specificity of the condition.
The qualified orthopedist who will undertake the treatment should take into account the age of the patient, his daily requirements, his general state of health, his compliance, the location of the involved joint, etc.
Treatment initially includes conservative means. The first recommendation made to the patient is the muscle strengthening of the affected area, in order to determine if with its help the symptoms can subside or even disappear.
If the above measure does not work, the following is the administration of preparations containing components of normal articular cartilage (glucosamines, chondroitins, hyaluronic acid, collagen) by oral administration.
Next come the direct injections of hyaluronic acid, growth factors (PRPs), mesenchymal cells and stem cells into the affected joint.
Next comes surgical solutions, which will usually solve the problem as well, since the above measures cannot deal with, at least, the most serious cases.
Radio frequency
This technique is applied arthroscopically and is effective for achieving a uniform surface along small gross lesions, usually first degree. However, the high intra-articular temperature associated with this method can partially or completely destroy the articular cartilage. Temperatures higher than 50°C have been defined as a critical threshold for chondrocyte death. In recent years, radiofrequency devices with temperature indicators have been developed so that temperatures can be monitored during arthroscopy.
Rubbing
It is an arthroscopic technique in which, in essence, mechanical cleaning is done. It was originally described as a palliative measure to try to avoid total knee arthroplasty in patients with early-stage osteoarthritis. It is thought that stimulation of subchondral bone can release mesenchymal cells from the bone marrow, thereby promoting the formation of new tissue.
Microfracture method
The oldest and technically least demanding solution is the arthroscopic technique of microfractures and microdrilling, through which communication channels are opened between the injured cartilage surface and the mesenchymal cell-rich subchondral bone. The process favors the production of fibrocartilaginous tissue that “fills” the cartilage deficit.
Transplantation of osteochondral cylinders
With this technique, osteochondral cylindrical pieces taken from an area of the diseased joint that is not loaded are placed in the area of the lesion.
The technique of implanting osteochondral cylinders is applied either arthroscopically or by open surgery, depending on the location and size of the lesion.
Autologous chondrocyte transplantation
“It is done in two stages. First, healthy cartilage is taken from a non-load bearing surface of the joint and sent to special centers for culture and growth of autologous chondrocytes. The patient is then readmitted to the operating room and the chondrocytes are arthroscopically implanted into the lesion. The great advantage of the method is that hyaline cartilage develops, qualitatively superior to fibrocartilaginous tissue and similar to the natural one,” the doctor points out.
Transplantation of large cartilage and osteochondral allografts
In cases where the articular cartilage lesions occupy a large surface area of the joint or, at the same time, the subchondral bone is also deeply affected, then the choice is the transplantation of large cartilage or osteochondral pieces from donors (grafts).
Autologous transplantation of specially treated cultured chondrocytes on tissue collagen substrate
Modern cartilage repair techniques rely on taking healthy cartilage tissue from the patient’s joint, culturing the chondrocytes isolated from the cartilage and reimplanting them in the area of the cartilage damage, where they will grow new articular cartilage.
These cells are transferred to the area of damage placed on special membranes made of collagen or hyaluronic acid (scaffolds). These two operations can be done in one operation, either open or arthroscopically.
Use of early stem cells (stem cells)
The doctor proceeds to take either a small amount of adipose tissue, usually from the abdominal area, or bone marrow from the patient’s hip bone. The material is then sent to laboratories specialized in regenerative biotechnology, where the stem cells are isolated and then cultured for 5-6 weeks. The final product is injected into the joint, where it will develop its healing and regenerative action.
Membranes – scaffolds
These are membranes (scaffolds) on which cultured cells are placed and these are then placed in the area of damage. The membranes offer protection to the cells as a stable substrate, adhesion to the area of damage so that they are not lost in the synovial fluid and are additionally loaded with growth factors that stimulate the cells to build new synovial cartilage.
Gene therapy
“Recently, gene therapy has found an important field in chondrogenesis research. Gene carriers or genetically modified chondrocytes or mesenchymal cells are placed at the site of the lesion, conditioned to produce growth factors that lead to the production of new articular cartilage (chondrogenesis). But this treatment is still in the research and experimental stage and has not been applied in clinical trials.
From the above it is clear that today there are several reliable solutions for a frequent problem for which, in the past, there were very few weapons in the therapeutic quiver of the orthopedist.
However, we should bear in mind that all the described solutions are effective only if the problem is correctly diagnosed and both the patient and the treatment are selected,” concludes Mr. Dobris.
Written by:
Mr. Dimitrios P. Dovris, Orthopedic Surgeon, Orthopedic Supervisor at the Metropolitan Hospital, Doctor of the University of Athens.
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