Autologous Chondrocyte Implantation (ACI)
Autologous chondrocyte implantation (ACI) is a procedure to treat the articular cartilage defects of the knee. This procedure is effective for treating small areas of cartilage damage that causes pain and swelling and restricts the range of motion. Autologous chondrocyte implantation is not indicated for those patients who have advanced arthritis of knee.
Autologous chondrocyte implantation is a two-stage procedure:
The first step is performed arthroscopically which evaluates the cartilage defect. If the defect is appropriate for an ACI procedure, the healthy cartilage cells are harvested from the non-weight bearing area of the bone. The healthy cartilage cells are then sent to the laboratory where the cells are cultured and multiplied over a 3- to 5-week period. Once enough cells have been grown, the patient undergoes a second procedure called arthrotomy or an open procedure.
In the second procedure a large incision is made to expose the area of cartilage damage. A second incision is then made over the shin bone and a "patch" is harvested from the periosteum, a thick tissue that covers the shin bone. This periosteal patch that is harvested is cut appropriately to match the size of the cartilage defect. The patch is then sewn over the cartilage defect and the cultured cells are injected underneath the periosteal patch which holds the new cartilage cells in the area of cartilage defect.
One of the most common complications of ACI is periosteal hypertrophy which occurs due to scar tissue formation around the edges of the periosteal patch. Other complications such as implant failure, knee infection and knee stiffness may also occur.
Following ACI procedure, you will not be allowed to bear weight for at least 6-8 weeks so that the cells adhere to the underlying bone. You may still observe limited range of motion for certain period of time.
The advantage of ACI procedure is that the cartilage cells are taken from the patient's own body; hence there is reduced risk of graft being rejected by the patient's own body. The disadvantage is that it is a two-step procedure and requires an open incision.