Any kind of surgery, no matter how simple, can have its problems. Postoperative complications can include infection or poor wound healing. In the case of autologous chondrocyte implantation (ACI), there are some additional unique problems that can occur.
ACI is a two- or three-step process. The procedure is done by taking normal, healthy cartilage cells from the patient. They use these cells to grow more cells and then reimplant the new batch of cells in the damaged area of the knee joint. The new cells usually adapt well to the new environment. That’s the three-step process. In a two-step procedure, a patch of healthy cells large enough to cover the defect is harvested and transplanted. This leaves out the middle step of growing extra cartilage cells in the laboratory setting.
Until recently, reports on the long-term results of this procedure and any complications have been limited. Small studies with only a few patients were reported on. But a group of three surgeons from Europe pooled their cases together and analyzed and reported on the results. They were specifically interested in looking at complications from the ACI procedure.
Three different ACI techniques were used. The three methods used were: 1) periosteum-covered ACI, 2) Chondrogide membrane covered ACI, and 3) a three-dimensional matrix-associated ACI. A group of over 300 patients who had one of these ACI procedures were followed to see which patients had the most problems after ACI and what those problems were.
They found four major problems after ACI: 1) hypertrophy, 2) disturbed or inadequate fusion, 3) delamination, 4) graft failure. Hypertrophy refers to overgrowth of the transplanted tissue. Insufficient fusion describes patients where the transplant just didn’t regenerate like it should. The edges between the healthy, normal tissue and the implanted cells don’t meld together to form a solid, smooth surface. Delamination is the separation of the cartilage layer from the bone underneath.
In a few cases, there was osteonecrosis (death of the bone underneath the cartilage transplant). In all cases, patients were diagnosed on the basis of pain and/or loss of function after the surgery. Symptoms occurred anywhere from the first six months up to three years later.
Right now, the treatment approach in revision surgery is to remove the damaged, dead, or insufficient tissue and regraft the defect. This usually results in a good return of function, but there are no studies yet on the clinical outcomes of revision surgery for failed ACI.