The destruction of articular cartilage is known as chondrolysis. While chondrolysis is rare anywhere in the body, it has been most common in the hip when conditions such as birth defects cause the bones in the hip to unnaturally press against each other. Prior to the 1990’s, chondrolysis of the shoulder was virtually unheard of. However, as doctors began experimenting with new surgical techniques and instruments, reports of shoulder chondrolysis began to appear.
When articular cartilage in the shoulder is destroyed, it leaves bone to rub against bone. At first this causes inflammation and pain in the bones. Later it leads to destruction of the surface of the bones. A shoulder transplant becomes the only treatment with a possibility of relieving the pain and allowing use of the shoulder.
A potential cause of chondrolysis is the use of a pain pump following any type of arthroscopic surgery in the shoulder. In the last decade or so, surgeons have begun leaving tiny plastic catheters (tubes) inside joints after surgeries like knee replacements and shoulder arthroscopies. They have found that bathing a joint after surgery with a local pain medication (a local anesthetic) diluted in water provides better pain relief than pain medications given by mouth or intravenously.
A “pain pump” is a small device that pumps the pain medication through the catheter and into the joint. After shoulder surgeries a pain pump would typically be left running for 48 hours. The most common pain medication used with pain pumps is the drug bupivacaine (the brand name is Marcaine). It is a powerful local anesthetic that has been used by surgeons for decades. When pain pumps began being used following shoulder surgery (which did not include thermal shrinkage), reports of patients who developed chondrolysis began to appear.
The recent chondrolysis cases appeared more frequently than usual, said McGowan Institute for Regenerative Medicine
faculty member Constance R. Chu, MD, PhD, an orthopedic surgeon and associate professor at the University of Pittsburgh who studies cartilage regeneration.
“When we see it happen quickly, it’s devastating and you start thinking, why did this happen?” she said.
In late 2006, after a handful of studies indicated that the pain pumps might be causing chondrolysis, the I-Flow Corporation, the largest pump manufacturer, changed its directions in package inserts to advise doctors to avoid placing the pump catheters in joints. In 2007, I-Flow posted a bulletin on its Web site notifying physicians of the risk.
“There’s no study that I’m aware of that shows a direct cause,” said Chu, who conducted several laboratory studies that found local anesthetics could kill cartilage cells.
Of her own research, she said, “I think it provides important information, but it’s a huge leap to say this is what’s going on in the patient.”
Illustration: The shoulder joint. –Wikipedia.
The New York Times (01/26/10)
Bio: Dr. Constance Chu
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