Red Sox second baseman Dustin Pedroia and knuckleballer Steven Wright are both on the disabled list with knee inflammation. Both underwent cartilage restoration to try to repair damage to the articular cartilage, which acts as a cushion between joints and allows for smooth, pain-free movement.
Cartilage damage can be caused by wear and tear or by a traumatic injury.
"[Lesions] do not always produce symptoms at first because there are no nerves in the cartilage," according to Dr. Riley Williams III of the Hospital for Special Surgery in New York, who performed the procedures on both Pedroia and Wright. "Over time, however, lesions can disrupt normal joint function and lead to pain, inflammation and limited mobility. The lesion may gradually worsen or cause other problems in the joint."
Cartilage is avascular, meaning there is no blood flow and no chance for cartilage to heal on its own.
There are various options for cartilage restoration.
"These procedures are designed to heal cartilage damage by filling the cartilage defect with repair tissue," according to Brigham and Women's Hospital.
Here is a look at four options, including the procedure performed on Pedroia and Wright:
Microfracture: The least invasive of the options, for smaller cartilage damage. It is performed using an arthroscope. The procedure involves poking small holes in the joint surface and bone underneath the cartilage to create blood flow. Along with that new blood supply come new cells that will form new healthy cartilage. "Resulting blood clots prompt the formation of a cartilage-like scar and regenerate repair tissue," according to John Hopkins Medicine.
Osteochondral autograft transfer: This procedure can be performed arthroscopically but sometimes requires an open incision. It is used when the damaged area is smaller. Cartilage from a non-weight-bearing part of the joint is put over the damaged cartilage. "[A] surgeon may take a single plug of cartilage or use multiple plugs. A procedure using multiple plugs is called mosaicplasty," according to the University of Utah Health Hospitals and Clinics.
Autologous chondrocyte implantation: This is a two-step procedure. The first step is done arthroscopically; the second step requires an open incision. First, healthy cartilage is harvested from a non-weight-bearing part of the joint. In a lab over three to five weeks, new cells are grown. Then in the second part of the procedure, a "biomembrane patch" is placed over the damaged cartilage and those new cells are injected behind it.
"ACI is most useful for younger patients who have single defects larger than 2 cm in diameter," according to the University of Utah Health Hospitals and Clinics. "ACI has the advantage of using the patient's own cells, so there is no danger of a patient rejecting the tissue."
Osteochondral allograft transplantation: This is the procedure Pedroia and Wright underwent, performed by Williams. It generally requires an open incision but can be performed arthroscopically. Tissue from a cadaver is sterilized, the damaged cartilage is removed, and the donor tissue is prepped to fit in the exact damaged area.
After the procedure, according to Williams, most patients will be on crutches for 6-12 weeks.
"Patients need to undergo a lengthy physical therapy program in order to restore range of motion and relieve pain and swelling on the joint," according to Williams. "Long-term follow-up care will be required in order to maintain the results of this procedure."
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