Articular cartilage defects in the knee is a common problem that typically leads to pain, loss of function and disability and may eventually result in debilitating osteoarthritis if not repaired. Conventional treatment options have included debridement, subchondral drilling, microfrACIure and abrasion arthroplasty, but over the past several years a new technique for cartilage transplantation has emerged in the United States as a fix for cartilage damaged knees. The new procedure, autologous chondrocyte implantation (ACI), can lead to the formation of hyaline-like cartilage in repair sites, which represents a significant advantage with respect to conventional techniques, according to a 2003 study published in the Journal of Orthopaedic Surgery. While early results for ACI show some success for people with certain symptoms, the procedure is not for everyone and is best suited for patients between the ages of 14 and 48 who are not overweight and have relatively healthy and well-aligned joints. “It is not designed to repair an arthritic knee,” says Dr. Jeffrey Dugas, an orthopedic surgeon with the Andrews Sports Medicine & Orthopaedic Center at St. Vincent’s Birmingham. Patients must also be able to undergo long and demanding rehabilitation following the surgical procedure. Dugas says that ACI was introduced in Sweden and was approved by the Federal Drug Administration for use in the U.S. in 1998. He and his associates have been doing the procedure since about 2000 but candidates for the surgery are not numerous. “The results for this procedure are patient selection driven,” Dugas says. “If you have the right patient with the right problem, the success rate is great and can be as high as 90 percent in healthy patients.” Dugas points out that ACI is not a quick procedure, because it involves the harvesting and growing of the patient’s chondrocyte cells in a laboratory for use in the transplant. He said a small biopsy, about the size of a Tic Tac, is taken from the joint surface. This specimen is placed into a culture medium controlled by the Boston-based Genzyme Corporation where the cells multiply over a six-week period. The implantation surgery requires an open approach to the knee, says Dugas. After trimming the defect to a stable rim and clearing the bony base, a copy of the defect is made from sterile paper and used to trace out the desired cut for harvesting a periosteal patch from the proximal tibia. “The patch is then transferred to the defect and sutured so that it forms a water-tight seal,” Dugas says. The cultured chondrocytes are then injected under the patch and the patch is finally sealed. While this method is producing satisfACIory results, Dugas says that trials are under way for a new tissue-engineering technique for treatment of deep cartilage defects in which autologous chondrocytes are seeded on a tri-dimensional scaffold provided by a bilayer collagen membrane. “With this method, the cells attach to the membrane which is used instead of the periosteal patch,” he says. The Journal of Orthopedic Surgery reports that the collagen membrane also offers some surgical advantages. It can be applied exclusively with fibrin glue which allows the surgeon to use a smaller surgical incision. This simplifies the procedure and shortens operating time. Dugas says membrane ACI is an exciting development in the area of cartilage repair and shows promise for further developments in the biologic resurfacing of joints. “Because it’s rare to have young, healthy people with the type of problems that require cartilage transplantation, we don’t have large numbers of patients to study,” Dugas says. “However, I’m excited about these developments and what they may mean to the field of orthopedic surgery. I believe we can really change lives with this technology.” October 2007