Patients often see an orthopedic surgeon about knee pain. There can be many reasons for knee pain, including injury, overuse, and arthritis. In recent years there have been many advances in orthopedic surgery, including advances in arthroscopic surgery and knee replacement.
But what can be done if someone injures a knee and damages part of the joint's surface? It is meant to be a smooth, gliding surface. Many patients with injuries or certain conditions are much too young to consider joint replacement. What options do they have?
Surgeons have several techniques to deal with these "potholes" on the joint surface. One is that they can drill small holes or create micro-fractures to stimulate a healing response, hoping a repair layer (though not the same as cartilage) will form. Another method includes the growth and injection of cartilage cells under a tissue patch sown over the defect. Or small plugs can be taken from less critical areas of the knee to be placed side by rise to fill the area, similar to a mosaic. Each of these methods has its advantages and disadvantages, and certain methods are more appropriate depending on the situation.
One of the most challenging problems is if the defect or pothole is large and in a critical position for bearing weight. One solution for this problem is an osteochondral allograft. Osteochondral means a graft that has both the cartilage surface and the underlying bone. Allograft means the tissue has been obtained from an organ or tissue donor. This technique resurfaces the joint with cartilage. It is necessary to have the underlying bone as a way to attach the plug-shaped graft, and many patients have a defect in the bone as well. To perform this procedure, a graft is needed from a tissue bank. This usually means the patient is put on a waiting list until a donor is available. A tissue bank can subdivide a knee to help multiple patients, sending only the needed part for each patient. Frequently asked questions are whether these grafts can be rejected and whether anti-rejection medicines are needed. Because cartilage has no blood vessels and the bone can be washed of most blood cells, anti-rejection medications are not needed.
When a graft is available, the surgery must be done within a few days while the cartilage cells are viable. The knee is opened with a small incision, and the defect, or hole, is drilled out to a round shape. Next, the same position on the graft is located and a "plug" of the same size is obtained using a coring reamer. The plug now fits in the hole to eliminate the defect. Small screws are sometimes used to help hold the graft in place while it heals to the surrounding bone.
After surgery, knee motion is started immediately, because motion is healthy for the joint surface and promotes healing. Patients use crutches for six weeks, because weight bearing might cause small amounts of motion that could interfere with healing.
While many patients have small defects and require no treatment, the less frequent, but more disabling, large defects may be addressed by an osteochondral allograft when few or no other options exist.