Microfracture is a surgical technique used to repair damaged articular cartilage by making multiple small holes in the surface of the joint to stimulate a healing response. The technique is frequently used in athletes after they injure their joints. While short-term results may often look promising, results often tend to deteriorate over time.
Why is this?
The surface of joints is covered with articular cartilage, the smooth bearing surface that has a dense matrix, few cells and no blood vessels. When injured by a fall or a sports injury, the dent in the articular cartilage never heals. If the injury is large enough to not only expose the underlying bone but to cause bleeding, a degree of healing can occur, usually with a repair tissue that is not the same as the normal cartilage. When the healing is inadequate, pain recurs.
Over time in the absence of healing, the initial damage to the articular cartilage gets worse, leading to osteoarthritis, the loss of cartilage and the deformation of the underlying bone. This explains the intense efforts by surgeons to repair these cartilage lesions before they become a bigger problem. The repair methods range from nonoperative injections of lubrication, growth factors and stem cells to operative interventions which range from microfracture, cartilage plugs, cells grown in culture, stem cell paste grafting or complete cartilage replacement.
Essentially all the techniques are trying to take a degradative situation, where the cartilage is going to wear down and make it into an anabolic environment where the cartilage is stimulated to regrow or repair.
Microfracture, by making holes into the underlying bone, brings a new blood supply to the surface; the blood supply carries the marrow progenitor or stem cells. The clot that forms on the top of the bone at the site of the cartilage injury must heal and mature into an effective repair tissue for the procedure to work. It often does form the clot, but clot has a varying ability to form into good enough cartilage repair material. The data from multiple studies in athletes shows that the repair tissue breaks down over a few years leaving the exposed bone to cause more pain. Microfracture fails because the body loses the race between durable healing and repeated injury from weight-bearing alone.
For microfracture alone to work consistently, it must be augmented. The healing tissue must be stimulated to form cartilage rapidly and durably. Our bias is to do this by adding progenitor-stem cells and bone paste to a supermicrofracture or morzelization of the lesion in a technique called paste grafting. We augment that healing process by injections of growth factors and hyaluronic acid lubrication injections at three months into the healing period. Other investigators are using variations of stem cells and growth factors in resorbable regeneration templates. Still others are testing new materials as cartilage replacements.
In normal walking each year, you take 2 million to 3 million steps at up to five times your body weight depending on the height of the step. When microfracture fails, it is because natural healing alone is simply not effective often enough on a surface that sees so much force, never mind the torque and stress of pivoting sports. Fortunately, the field is advancing fast enough so that the injuries we see today are likely to receive treatments designed to more permanently repair the damage.
Now, if we could only avoid doing the damage in the first place.
Dr. Kevin R. Stone is an orthopedic surgeon at The Stone Clinic and chairman of the Stone Research Foundation in San Francisco. He pioneers advanced orthopedic surgical and rehabilitation techniques to repair, regenerate and replace damaged cartilage and ligaments. For more info, visit www.stoneclinic.com.