What is MACI?

Matrix-induced autologous chondrocyte implantation (MACI) is a surgery used to repair cartilage damage in the knee. It uses a patient’s own cells to help regenerate new cartilage. This procedure is used to treat full-thickness cartilage defects, meaning the cartilage is completely damaged or worn away. MACI is especially helpful for people who have pain but no bone loss or severe cartilage degeneration. It is the first FDA-approved treatment of its kind and works by using the body’s own healing process to restore damaged cartilage.

MACI is a two-step procedure:

Step One:

• A small sample of cartilage, about the size of a tic-tac, is taken from the knee using a minimally invasive arthroscopic surgery.
• This sample is sent to a laboratory, where the cartilage cells (called chondrocytes) are grown for 4-6 weeks to increase their numbers.

Step Two:

• The grown cartilage cells are placed onto a special collagen membrane.
• The membrane with the cells is then implanted back into the damaged area of the knee.
• The cells encourage the growth of new cartilage, helping to restore the knee’s flexibility and reduce pain.

What is Articular Cartilage in the Knee?

Articular cartilage is a smooth, slippery tissue that covers the ends of the bones in the knee. This cartilage helps the bones glide smoothly over each other without friction or pain, much like the cartilage you see at the end of a chicken bone. Over time, or after an injury, this cartilage can wear down or get damaged. Since cartilage does not have a blood supply, it cannot heal itself. If it continues to break down, it can lead to pain and osteoarthritis, a condition where the bones rub directly against each other. MACI helps repair this damage by using the body’s own cells to regrow the cartilage.

Would I Benefit from MACI?

MACI is a great option for patients with isolated cartilage injuries or defects in the knee. However, it’s not right for everyone. The best candidates for MACI include:

• Patients with pain from cartilage damage in the knee.
• People with patellar instability (knee cap problems) along with cartilage damage in the knee.
• Patients with damage in the tibiofemoral region of the knee (where the femur and tibia meet).
• People aged 18 to 50.

How Long is the Recovery Following MACI Surgery?

MACI is a two-step procedure, and recovery happens in two parts:

Step 1: After the Cartilage Biopsy:

• After the cartilage sample is taken, you can go home the same day.
• You can bear weight on your knee as tolerated, and most people return to work in a few days.

Step 2: After the MACI Implantation:

• You’ll go home the same day as the surgery.
• You will need to wear a knee brace for 6 weeks
• Weight-bearing after surgery will depend on where the cartilage is repaired, but usually, you can put full weight on the knee within 6 weeks.
• Physical therapy will begin 1-2 weeks after surgery and should be followed exactly as prescribed.
• Return to work will depend on the physical demands of your job.
• Most patients can return to high-impact activities (like running or sports) after 9-12 months, once the knee has healed and the tissue has grown back.

Does MACI Work?

MACI has proven to be effective for most patients. Patients who are good candidates for the procedure, many people experience significant improvement in knee pain and function. The new articular cartilage grows in the damaged area, allowing many patients to return to normal activities like work and sports.