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Repairing Articular Cartilage
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The glistening white tissue that cover the ends of the bones (the joint surface) is both tough and resilient. It is not only important for smooth gliding of the joint, but also to “soften” the impact during loading, much the same as a shock absorber. Articular cartilage may not appear to be alive, but in fact it is. The number of cells (chondrocytes) which reside in the tissue is indeed small (approximately 1-5%), but they have the job of keeping the matrix around them healthy. Think of the cells as the few marshmallows suspended in a jello (the matrix) mold. As with most body tissues, there is a constant wear out and replacement activity of this matrix. The cells (marshmallows) keep the matrix (jello) repaired. Unfortuately, the cell themselves do not replicate.

Once the cells are damaged or lost, the surrounding matrix gradually degenerates. Without help, the body is typically not able to repair these articular cartilage defects.
It is at that point when the Orthopaedic Surgeons at CRA of New York consider helping the body start a healing response.

Early Intervention
The New York CRA offers several options for regeneration and/or repair of damaged articular cartilage. From the proceeding discussion, it is easy to appreciate the need for early intervention. Without intervention, degeneration may proceed.

Arthroscopic Chondroplasty and Microfracture
For patients who have had the meniscus removed, the surgeon may offer an innovative solution called a meniscal transplant. It is important to remember that even though only a part of the meniscus was removed, at times the effect to the knee from a biomechanical standpoint is the same as a total menisectomy. The indications for transplant need to be assessed by your cartilage surgeon. Unlike other forms of tissue transplantation, this procedure does not require patients to be on medications to prevent rejection. Intermediate term follow-up studies in the literature are encouraging.

Repairing Larger Defects
For patients with more extensive cartilage damage, CRA offers a range of methods for cartilage restoration using a variety of approaches:

Osteochondral Autograft

This technique is analogous to a hair-plug transfer. The surgeon removes a small section of the patient’s own cartilage along with the underlying bone plug. This is obtained from an area which does not participate in high loading.

This bone and cartilage (hence osteo—chondral) local graft is then transfered to the defect where a receiving hole has been prepared. Obviously, there is a limit to the amount of tissue available for “harvesting”. The typical site of harvest is at the margin of the femoral trochlea where the patella glides—if that area is involved with damage then this technique may not be possible. The size of the defect treatable with this method is usually between 1 and 2 square cm or slightly larger than a thumbnail.


Autologous Cartilage Cell Implantation

 
For articular cartilage defects greater than 2cm2, one of the more advanced techniques for cartilage regeneration is ACI (Autologous Chondrocyte Implantation). This technique originated in NYC at the Hospital for Joint Diseases. David S. Menche, M.D., the founding member of CRA, was an integral member of the research team that developed the procedure of autologous chondrocyte transplantation in the early 1980's. In 1987, Dr. Lars Peterson in Sweden performed the first chondrocyte transplant in the world. The technique of ACI became available in the U.S. in 1995. Dr. Menche performed the first chondrocyte transplant in New York in that year.

The first stage may be performed when initially assessing the joint arthroscopically. A small amount of the patient’s own articular cartilage is harvested. Through cell culturing techniques, the cell number is increased from a few hundred thousand to over 10 million cells. These autologous (your own) cultured cells are then implanted in the knee in a second surgical procedure to repair and resurface areas of cartilage loss. As per the analogy on page 5, the cells (the marshmallows) represent only 1-5% of the volume of the matrix (jello). These cells must synthesize (create) matrix over several months to reestablish the articular surface.


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