COLUMBIA — Patients who have formerly had to wait three to nine months for joint surgery could have a shorter wait and better-quality transplants in their future as a result of a new tissue storage system developed by MU researchers.
Joint surgeries rely on cartilage tissue from organ donors, and the new system allows donor tissue to be stored for 63 days — more than twice as long as the current system used by most tissue banks.
The system developed at MU has been used clinically with canines at the Veterinary Medical Teaching Hospital for five years. Researchers are now in the process of licensing with a tissue bank, so that it can be available to humans, too.
James Cook, director of the Comparative Orthopaedic Laboratory at MU and the study's lead researcher, said in an email that he hopes the storage technology will be in use with patients at the Missouri Orthopaedic Institute by late 2012 or early 2013.
Before a joint surgery can happen, a surgeon decides that a patient with a cartilage defect, whether from trauma, injury or arthritis, needs an osteochondral allograft — "living bone and cartilage from an organ donor," Cook said. The patient then waits for a matching graft to be located at a tissue bank.
Most tissue banks use the same storage system, which involves refrigerating grafts at 4 degrees Celsius. The banks operate on a 28-day deadline from the day that an organ donor's graft is received to the day of a patient's joint surgery, Cook said. Studies have shown that after 28 days, a graft's cell viability — the ratio of living to dead cells — goes below 70 percent, which is the lowest acceptable level for usage.
Tissue banks currently throw away 80 percent of donated grafts, Cook said, because donated tissue cannot be matched to a patient within the 28-day time frame.
"Because of the strict storage time frame you have, there is very seldom a graft available the moment you get diagnosed as needing a surgery," said Aaron Stoker, an assistant professor at MU and another of the team's three main researchers.
Stoker had a knee surgery last year, and it took three months from the diagnosis until doctors were able to locate a graft that matched his size parameters.
Cook said the wait is sometimes as long as nine months.
The new storage system would maintain high-quality grafts, meaning tissue with 90 percent cell viability, for at least 63 days after harvest, Cook said. This translates to a larger supply of available cartilage tissue, and therefore a shortened wait for patients.
The doubled life span is achieved with a combination of the temperature (25 degrees Celsius), container, storage solution and individual quality testing of each graft, which is not possible in the system most tissue banks currently use.
Quality testing and higher cell viability increase the likelihood that a patient won't need a second surgery, Stoker said.
The study will be published in the Journal of Knee Surgery in April. Although the system has only been tested fully for use in knees, Cook said the method is amenable for the other major joint surgeries, such as ankle, shoulder, elbow and hip.
Stoker said others have created systems that allow for cell viability to be sustained at a higher level to the end of the 28 days, but not longer.
"We were the first and certainly the only ones so far to be able to extend it to this timeline," Cook said.