Matrix-induced autologous chondrocyte implantation or MACI is a procedure in which a patient’s own cells are used to regrow new cartilage for the knee joint. Because of this, it is a two-part procedure.
Symptoms of these conditions include sharp or dull pain in the front of the knee that is amplified by sitting for long periods of time, climbing and descending stairs, or any activities in day to day life or working out that involve a squatting motion. Patellar instability symptoms include the kneecap coming off its track and subluxing or dislocating. At HSS, candidates for MACI will be evaluated by their surgeon using both a physical examination as well as magnetic resonance imaging (MRI) to provide the clearest picture of the cartilage injury present in the knee.
During the first operation, the surgeon views the knee through two small portals (one medial, one lateral). Using a very small camera, the surgeon can look inside the knee to examine the condition of the cartilage. If necessary, the surgeon may debride—remove damaged tissue—from the knee, and then will take a biopsy of the patient’s cartilage. This procedure takes around 30 minutes. The biopsy is then sent to the lab to grow on a collagen matrix for approximately one month. This allows the cartilage to be relatively stable when it is inserted back into the knee during stage two of the procedure.
During the second operation, the surgeon cuts the MACI implant grown in the lab to the exact size of the defect in the patient’s knee. The implant is then glued onto the defect. This procedure takes approximately one hour and involves a 2-inch incision. The second operation is where a combined procedure would take place (such as tibial tubercle osteotomy or MPFL reconstruction) if needed.
Since MACI is a two-step procedure, there will be two recoveries following each of the stages.
Patients who are good candidates for MACI should expect significant improvement in knee pain and function. Goals should be discussed with your surgeon prior to selecting a procedure, but patients are often able to return to sports and activities that their knee pain was preventing them from participating in. As with any surgery, there are risks that should be discussed with your surgeon before undergoing MACI surgery.