David Menche M.D.
Repairing Articular Cartilage
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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. 


Early Intervention

 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 the procedures described below may be prescribed.


Osteochondral Autograft

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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

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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. 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.These cells must synthesize (create) matrix over several months to reestablish the articular surface.





Osteochondral Allograft

For larger defects of both bone and cartilage loss, surgeons may custom fit an implant of freshly donated cartilage and bone. This transplant may allow restoration of the joint surface.


Future Techniques

rac_6Biologic tissue engineering is continuing to bring exciting new approaches from the lab to the clinical arena. It may be possible to use primitive cells from the bone marrow or periosteum (which have the potential to develop into several different types of cells, thus called pluripotential cells or in this case mesenchymal stem cells) and induce them to transform into hyaline cartilage. A variety of growth factors or local hormones may also come into play in creating the right “local environment” for hyaline cartilage to develop and remain healthy or even allow the hyaline cartilage to heal itself. Genetic reprogramming may in time replace surgery—but not at this point in the new millennium.

Other biopatches may have the predominant purpose of acting as a temporary home for chondrocytes or “pre-chondrocytes”. They may be used to deliver and maintain the cells in proper position until the healing response takes effect. This exciting field will offer many new surprises which will hopefully lead to opportunities for restoring function in less and less invasive means.


Established Arthritis

Many patients suffer for years with arthritis that limits even the simplest activities.  Fortunately, joint reconstruction surgeons have a wide range of methods to relieve pain and help restore function.


Injectable Viscosupplementation:

Surgeons inject the knee with a substance that may offer relief by possibly improving both joint lubrication in the short term and the biochemical enviroment in the intermediate term. The injectable options will continue to evolve.

Intra-articular (into the joint) injections of a natural lubricant (not cortisone) are now available as an FDA-approved procedure for the treatment of osteoarthritis.  Results are variable and dependent on the degree of osteoarthritis present. When symptomatic improvement occurs, significant relief of symptoms can last for six months or longer..


Osteotomy:

When the bones do not align properly, joint forces are not evenly distributed and may overload one side causing pain and possibly degeneration. With an osteotomy (means cut in the bone), the surgeon cuts the femur or tibia and then realigns the bones.

After healing, the bones are in a new position and force (weight) is shifted from the overloaded or damaged side to the more normal or underloaded side of the joint

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Unicompartmental Joint Replacement:

This procedure replaces only the damaged portion of the joint with metal and/or plastic, leaving the remainder of the joint intact.


Total Joint Replacement:

If there is extensive damage which precludes the use of the above procedures, then all of the knee joint surface is replaced with artificial components allowing most patients to return to limited pain-free activities.