Matrix-induced chondrocyte implantation (MACI)

What is matrix-induced chondrocyte implantation (MACI)?

Matrix-Induced Chondrocyte Implantation, or MACI, is a type of knee surgery used to repair damaged cartilage. Cartilage is the smooth tissue that covers the ends of bones in a joint, helping them move easily without pain. In MACI, your own cartilage cells (called chondrocytes) are collected, grown in a lab, and placed on to a special patch. This patch is then implanted into the damaged area inside the knee to help the cartilage heal.

What can the MACI procedure be used to treat?

MACI is mainly used to treat cartilage damage in the knee, especially when there is a cartilage defect. It can help people who have pain, swelling, and difficulty moving their knee because of this damage. It’s often recommended for people who are active and younger than 55 years old, although it can be considered for older adults in good health.

What is the difference between MACI and ACI?

Both MACI and Autologous Chondrocyte Implantation (ACI) use your own cells to repair damaged cartilage in a joint. MACI uses your own cartilage cells to repair damage in the joint, growing them on a supportive scaffold (matrix) before implantation for improved placement. In contrast, ACI implants the cells directly into the joint and secures them with a patch.

How does the MACI treatment work?

The treatment happens in two parts:

1. Cartilage cells are taken from a healthy area of your knee during a small keyhole (arthroscopic) surgery.
2. These cells are sent to a lab where they are grown on a flexible patch made of natural material.
3. After several weeks, the new patch with the cartilage cells is implanted into the damaged area of the knee during a second operation. The cells grow and repair the damaged cartilage over time.

Is MACI right for me?

MACI might be suitable for you if:

• You are younger than 55 (though sometimes older)
• You have painful cartilage damage in your knee
• You’ve tried other treatments like physiotherapy or medication without success
• You are active and want to return to sports or exercise

Your consultant will check the size and location of the cartilage defect with an MRI scan and sometimes an arthroscopy (keyhole surgery) before recommending MACI.

What happens during a MACI procedure for knee cartilage repair?

The MACI procedure has two main steps:

1. First surgery (arthroscopy): A small amount of healthy cartilage is taken from your knee. This takes about 30 minutes.
2. Second surgery (implantation): After the lab grows your cartilage cells (which takes around 4–6 weeks), you have an open knee surgery. The surgeon cleans the damaged area and attaches the MACI patch to it with a special glue.

Preparing for matrix-induced chondrocyte implantation (MACI)

Before the procedure:

• You’ll have a consultation with your surgeon to discuss your symptoms and treatment options.
• You may need MRI scans or an arthroscopy.
• You’ll be given instructions about fasting (not eating) before surgery and how to manage your medications.

Recovery from MACI knee cartilage repair

Recovery takes time and happens in stages:

• You’ll need crutches for 6–8 weeks to avoid putting weight on the knee.
• A physiotherapy program will help strengthen your knee and improve movement.
• It can take 6 months to a year before you’re back to full activity, especially for sports.

What are the benefits of MACI treatment?

• The procedure uses your own cartilage cells, reducing the chance of rejection.
• It can relieve pain and improve knee movement.
• It may allow you to return to sports and daily activities.
• It can help preserve the natural knee joint, delaying or avoiding the need for a knee replacement.

How long do the benefits of the MACI procedure last?

The benefits of MACI can last for at least 5 to 10 years, and sometimes longer. Success depends on factors like age, activity level, and how well you follow your recovery program.

What are the risks of matrix-induced chondrocyte implantation?

As with any surgery, there are risks such as:

• Infection
• Blood clots
• Joint stiffness
• Graft failure (the implanted patch might not heal properly)
• Ongoing pain or swelling

Your surgeon will explain these risks to you before surgery.

Common side effects of MACI treatment

Some people experience:

• Knee swelling
• Stiffness
• Mild discomfort
• A feeling of tightness where the patch was placed

These usually improve as you recover.

Are there alternative treatments for knee cartilage repair?

Yes, alternatives include:

• Microfracture surgery: tiny holes are made in the bone to stimulate cartilage growth.
• Osteochondral grafting: healthy cartilage is moved from one part of your joint to another.
• Knee realignment surgery: the weight bearing axis of the lower leg can be changed to offload the damaged cartilage.
• Knee replacement: used for severe, widespread damage (often in older adults).

Your surgeon will help decide the best option for you.

How much does MACI treatment cost?

Click here and select your local Nuffield Health hospital to find the guide prices for MACI. Please note that the guide price stated is an approximate cost of treatment only. You will be given a fixed all-inclusive price for treatment following your initial consultation with a consultant.