The U.S. Food and Drug administration recently granted approval to a new knee implant that researchers say will outlive any on the market, giving recipients new hope that their artificial knees will not have to be replaced. Patients with advanced osteoarthritis or other degenerative conditions of the knee may undergo a knee arthroplasty or "total knee replacement" to alleviate the pain and friction caused by the condition. In the procedure, a surgeon removes a patient's knee and replaces it with synthetic parts. The ends of the two leg bones closest to the knee are then removed and replaced with metal and plastic caps. Over time, however, the motion inside the joint can break down these materials, causing the artificial knee to crack, flake, and pit. The debris this motion creates may cause osteolysis, a reaction to stray particles inside the joint. Osteolysis eventually forces the recipient to undergo a second operation with another implant.
The Durasul implant, marketed by Sulzer Orthopedics, may solve this dilemma. By using a special, wear-resistent polyethylene material, Sulzer hopes, the artificial knee, which was approved by the FDA October 26, will stand up to the rigors of the joint. "I would expect it to have extremely low wear," says Steven Whitlock, general manager for products at Sulzer Orthopedics. Clinical tests suggest that the material shows no measurable wear after 27 million cycles, the equivalent of 27 years in a human body. However, Whitlock admits, the implant's projected success is based on laboratory findings. Furthermore, transplants using the system have yet to take place in the United States.
However, the Durasul material has been used in hip replacements since 1998, and has received great marks so far. Clinical trials on the hip replacement system are being organized to demonstrate its effectiveness, and Sulzer hopes to amass a clinical study for the Durasul knee implant in the second quarter of next year. For now, the push is toward a full commercial release of the product, Whitlock says.
As new technologies emerge, patients with severe knee pain are given more hope that the available cures will endure.
