Articular cartilage repair

The aim of an articular cartilage repair treatment is to restore the surface of an articular joint's hyaline cartilage. Over the last decades, surgeons and researchers have been working hard to elaborate surgical cartilage repair interventions. Though these solutions do not perfectly "restore" articular cartilage, some of the latest technologies start to bring very promising results in "repairing" cartilage from traumatic injuries or chondropathies. These treatments are especially targeted by patients who suffer from articular cartilage damage. They provide pain relief while at the same time slowing down the progression of damage or considerably delaying joint replacement (knee replacement) surgery. Most importantly, articular cartilage repair treatments help patients to return to their original lifestyle; regaining mobility, going back to work and even practicing sports again.

Different articular cartilage repair procedures

Though the different articular cartilage procedures differ in the used technologies and surgical techniques, they all share the aim to repair articular cartilage whilst keeping options open for alternative treatments in the future. Broadly taken, there are four major types of articular cartilage repair:

Arthroscopic Lavage / Debridement

Arthroscopic lavage is a "cleaning up" procedure of the knee joint. This short term solution is not considered an articular cartilage repair procedure but rather a "palliative treatment" to reduce pain, mechanical restriction and inflamation. Lavage focusses on removing degenerative articular cartilage flaps and fibrous tissue. The main target group are patients with very small defects of the articular cartilage.

Marrow Stimulation Techniques (Microfracture Surgery and others)

Marrow stimulating techniques attempt to solve articular cartilage damage through an arthroscopic procedure. Firstly, damaged cartilage is drilled or punched until the underlying bone is exposed. By doing this, the subchondral bone is perforated to generate a blood clot within the defect. Studies, however, have shown that marrow stimulation techniques often have insufficiently filled the chondral defect and the repair material is often fibrocartilage (which is not as good mechanically as hyaline cartilage). The blood clot takes about 8 weeks to become fibrous tissue and it takes 4 months to become fibrocartilage. This has implications for the rehabilitation.

Further on, chances are high that after only 1 or 2 years of the surgery symptoms start to return as the fibrocartilage wears away, forcing the patient to reengage in articular cartilage repair. This is not always the case and microfracture surgery is therefore considered to be an "intermediate" step.

Osteochondral Autografts and Allografts

This technique/repair requires transplant sections of bone and cartilage. First, the damaged section of bone and cartilage is removed from the joint. Then a new healthy dowel of bone with its cartilage covering is punched out of the same joint and replanted into the hole left from removing the old damaged bone and cartilage. The healthy bone and cartilage are taken from areas of low stress in the joint so as to prevent weakening the joint. Depending on the severity and overall size of the damage multiple plugs or dowels may be required to adequately repair the joint, which becomes difficult for Osteochondral Autografts. For Osteochondral Allografts the plugs are taken from deceased donors. This has the advantage that more osteochondral tissue is available and larger damages can be repaired. There are, however, ethical considerations and worries on the histocompability.

Cell Based Repairs

Aiming to obtain the best possible results, scientists have strived to replace damaged articular cartilage with autologous cartilage of the same kind. Previous repair procedures, however, always generated fibrocartilage or at best a combination of hyaline and fibrocartilage repair tissue. Autologous Chondrocyte Implantation (ACI) procedures are cell based repairs that aim to provide complete hyaline repair tissues.

Cell based articular cartilage repair procedures take place in three stages. In a first stage, chondrocyte cells are extracted arthroscopically from a non load-bearing area from either the intercondylar notch or the superior ridge of the medial or lateral femoral chondyles of the patient. These cells, that are originally harvested, are grown "in vitro" in specialised laboratories for approximately four to six weeks until there are enough cells to reintroduce on the damaged area of the articular cartilage. The patient then undergoes a second surgery, in which the chondrocyte cells are applied on the damaged area. These cells then adapt themselves to their environment, forming new cartilage. During this surgery, chondrocyte cells can be injected, applied on the damaged area in combination with a membrane or implanted in a matrix structure. All procedures have their advantages and disadvantages.

The latest development in cell based cartilage repairs consists of "characterizing" the chondrocyte cells which will be implanted. Characterized chondrocyte cells form a much higher quality hyaline cartilage than ordinary chondrocyte cells. They are, therefore, believed to be more durable than average autologous chondrocyte cells. In February 2008, a scientific article in the "American Journal of Sports Medicine" prooved that Characterized Chondrocyte Implantation (CCI) results in better structural repair than microfracture surgery when treating symptomatic cartilage defects of the knee. [ The American Journal of Sports Medicine, volume 36 number 2, pp 235-246, February 2008]

Autologous Mesenchymal Stem Cell Transplant

For years, the concept of harvesting stem cells and re-implanting them into one's own body to regenerate organs and tissues has been embraced and researched in animal models. In particular, mesenchymal stem cells have been shown in animal models to regenerate cartilage [1] . Recently, there has been a published case report of successful cartilage growth in human knees using autologous mesenchymal stem cells. [2] [2] An advantage to this approach is that a person's own stem cells are used, avoiding transmission of genetic diseases. It is also minimally invasive, minimally painful and has a very short recovery period. This promising alternative to the current available treatments was pioneered by Regenerative Sciences [3] (Broomfield, Colorado).See also Autologous Mesenchymal Stem Cell Transplant for Cartilage Growth

The importance of rehabilitation in articular cartilage repair

Rehabilitation following any articular cartilage repair procedure is paramount for the success of any articular cartilage resurfacing technique. The rehabilitation is often long and demanding. The main reason is that it takes a long time for the cartilage cells to adapt and mature into repair tissue. Cartilage is a slow adapting substance. Where a muscle takes approximately 35 weeks to fully adapt itself, cartilage only undergoes 75% adaptation in 2 years. Karen Hambly: [http://www.cartilagehealth.com/acr.html Articular Cartilage Repair of the Knee] Cartilagehealth.com] If the rehabilitation period is too short, the cartilage repair might be put under too much stress, causing the repair to fail.

Concerns

New research by Dr. Robert Litchfield, September 2008, of the University of Western Ontario concluded that routinely practised knee surgery is ineffective at reducing joint pain or improving joint function in people with osteoarthritis. The researchers did however find that arthroscopic surgery did help a minority of patients with milder symptoms, large tears or other damage to the meniscus — cartilage pads that act like shock absorbers between upper and lower leg bones. [ [http://www.cbc.ca/health/story/2008/09/10/knee-surgery.html Therapy for arthritic knees often as effective as surgery: study] ]

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