OsteoArticular Transfer System (OATS) is the only procedure that replaces defects in articular cartilage with articular cartilage. Articular, or hyaline, cartilage is the smooth cartilage that covers the bone in the knee and other joints. Damage to it usually occurs through traumatic events and repair has been elusive. OATS is a surgical method of repair that has had early clinical success. Limitations of OATS include the inability to repair large and deep osteochondral defects, limited availability, possible damage to donor sites, and incomplete integration of the donor and recipient cartilage.
The ideal chondral (cartilage) defect is a relatively small, full-thickness defect between 10 to 20 millimeters. Larger chondral defects are not conducive to the OATS procedure due to limited availability of donor graft and the inability to reconstruct subchondral bone.
The orthopedic surgeon selects the cartilage donor site and accesses the area through a standard lateral portal. Next, she inspects the chondral defect arthroscopically, and the size of the lesion measured. A donor graft harvester is placed in the joint over the selected articular cartilage harvest site. Once the depth has been ascertained, the surgeon removes the harvester.
The next step is recipient socket creation. The tubular harvester is positioned to cover the defect and is driven into the subchondral bone approximately 13 millimeters. An alignment stick measures the recipient socket depth in relation to the insertion portal. Finally, the donor tube harvester is inserted into the recipient socket. A mallet is used to drive the graft into the socket, until the articular cartilage is flush with the recipient cartilage.
Donor sockets are usually left open after harvesting. They will fill with bone and fibrocartilage within 12 weeks of harvesting. After one year the donor site is filled with fibrocartilage. Bone removed from the recipient area may be inserted into the donor site.
Immediately following surgery, a patient begins rehabilitation. Range-of-motion exercises and protected weight bearing are essential to post-operative care, with increased weight bearing as the patient improves. An OATS patient may anticipate using crutches for six to twelve weeks.
The integration of donor-donor and donor-recipient articular cartilage interface is a risk with OATS. In addition, OATS can be performed only on defects of certain depths and sizes. Donor-site morbidity is a concern. Complications include pain, avascular necrosis, and fracture. Surgical complications—such as hemarthrosis, effusion, and pain—may also arise.
Medication may be needed to alleviate surgical pain.
See Your Doctor If:
Follow up if you experience swelling or pain in the recipient or donor area.
Last updated: 26-Oct-01