Autologous chondrocyte implantation
Autologous chondrocyte implantation (ACI) is a procedure to treat articular cartilage defects of the knee. This procedure is effective for treating small areas of cartilage damage that cause pain and swelling or restrict 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, healthy cartilage cells are harvested from a non-weight bearing area of the joint surface. 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 using an arthrotomy or an ‘open joint’ procedure.
In the second procedure, an incision is made to expose the area of cartilage damage. A second incision may then made over the front of the leg and a “patch” is harvested from the periosteum (a connective tissue that covers the shin bone). This periosteal patch 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 the cartilage defect.
One complication of ACI is periosteal hypertrophy which may occur due to scar tissue formation around the edges of the periosteal patch. Other complications such as graft failure, knee infection and knee stiffness may also occur.
Following an 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 an 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. Principle disadvantages are that it is an expensive, two-step procedure and requires an open incision. The National Institute of Clinical Excellence (NICE) have recently placed restrictions on this procedure.