Ask a Sports Doc: Regrowing cartilage to fix joint pain
January 21, 2014
Question: Doc, I'm 54 years old and have been skiing all my life. Now I'm suffering from osteoarthritis in my knees. I've heard there are new treatments available using your body's own stem cells to reproduce new cartilage. Is this true and how does it work?
Answer: Active sports enthusiasts often face the challenge of worn out articular cartilage in major joints such as the knee and shoulder. Replacing worn articular cartilage has been and continues to be the "Holy Grail" of orthopedics.
When I explain articular cartilage to patients in the office, I commonly refer to the smooth white coating you find on the ends of chicken bones. This is much like the cartilage that we have on the ends of our bones.
In a complex hinge joint like the knee, the articular cartilage coating is just a thin layer of 4-5 millimeters on the end of the femur, or thigh bone, and the end of the tibia, or shin bone. This cartilage has a very low coefficient of friction such that there is smooth gliding and sliding between the two bones which allows for full joint range of motion. When the cartilage is worn down, the condition is referred to as osteoarthritis. The symptoms include joint pain, swelling and decreased range of motion.
The repetitive stress of a particular sport such as mogul skiing can sometimes produce osteoarthritis in younger patients, but mainly we see worn articular cartilage in older patients. That's because as we age, the articular cartilage slowly breaks down and becomes thinner, not unlike treads on a tire wearing down.
For decades, orthopedists have used microfracture techniques to address worn cartilage in a patient.
Microfracture is the process of drilling, burring or picking areas of exposed bone in an effort to try to get articular cartilage to grow back in a given area of the knee. The results of microfracture have been limited and somewhat discouraging, as the process stimulates all major cell types to grow in an arthritic area, including bone cells and fibrous tissue. The bottom line is that microfracture does not result in a surface that is pure cartilage.
Instead, I am utilizing an exciting new technique called ACI, or autologous chondrocyte implantation. ACI uses the patient's own cartilage cells to grow a new cartilage implant. The ACI procedure takes a small sample of cartilage cells from a patient's affected knee in a simple arthroscopic procedure. These cells are then sent to a lab that isolates the cartilage cells and multiplies them in a culture over a 4-6 week period of time. The cells are then reimplanted back into the knee where the defect exists. The result is a cartilage surface that more closely resembles normal articular cartilage.
To determine if a patient is a candidate for ACI, we start with a thorough patient exam and a high resolution MRI, or magnetic resonance imaging.
I will still perform microfracture when it is indicated. Generally, microfracture works best on younger patients with smaller areas of worn cartilage. However, for older patients and those with larger affected areas, I am getting better results with ACI. Patients are returning to their normal activities with less pain and better range of motion.
Dr. Rick Cunningham is a sports medicine specialist with Vail-Summit Orthopaedics. Do you have a sports medicine question you'd like him to answer in this column? Visit his website at http://www.vailknee.com to submit your query.
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