Matrix-Assisted Chondrocyte Implantation (MACI)

Matrix-Assisted Chondrocyte Implantation, commonly known as MACI, is a cartilage restoration procedure used to treat focal cartilage defects in the knee. A focal cartilage defect is a localized area of damaged cartilage surrounded by otherwise healthy cartilage. These injuries can occur from sports injuries, trauma, repetitive stress, or previous knee problems.

MACI is a form of autologous chondrocyte implantation, meaning it uses the patient’s own cartilage cells to help regenerate cartilage within the damaged area. The procedure combines advanced cell culture technology with a specialized collagen membrane that serves as a scaffold for cartilage growth.

The goal of MACI is not simply to cover the damaged area, but to help restore cartilage tissue that more closely resembles the knee’s natural cartilage. This can improve pain, function, and quality of life while potentially delaying arthritis progression.

MACI is typically recommended for patients with symptomatic focal cartilage defects in the knee who have not achieved adequate relief with non-surgical treatments.

Candidates often include active individuals who experience persistent knee pain, swelling, or mechanical symptoms caused by a cartilage injury. The procedure is commonly used for cartilage defects on the femur (thigh bone), patella (kneecap), or trochlea of the knee (the groove at the end of the thigh bone that guides your kneecap during knee movement.

Dr. Brian Waterman must thoroughly evaluate you to determine whether MACI is the most appropriate treatment option. Imaging studies such as X-rays and MRI scans are often used to evaluate the size, location, and severity of the cartilage injury.

MACI aims to regenerate cartilage in an area of damaged cartilage. The procedure uses the patient’s own cartilage cells, called chondrocytes, which produce and maintain healthy cartilage tissue.

These cells are grown in a laboratory and placed onto a collagen membrane. Once implanted into the cartilage defect, the cells continue to multiply and produce cartilage matrix. Over time, the implanted cells help fill the defect and create new cartilage tissue.

By restoring the damaged cartilage surface, MACI aims to reduce pain, improve knee function, enhance joint mechanics, and allow patients to return to many of their desired activities. Restoring a smoother cartilage surface may also reduce abnormal stress on surrounding cartilage and joint structures.

MACI is performed in two stages.

The first stage involves a minimally invasive arthroscopic procedure. During this surgery, Dr. Waterman evaluates the cartilage injury and obtains a small sample of healthy cartilage from a non-weight-bearing area of the knee. This cartilage biopsy is sent to a specialized laboratory.

At the laboratory, chondrocytes (cartilage cells) are isolated from the cartilage sample and multiplied over several weeks. The cells are then seeded onto a collagen membrane to create the customized MACI implant.

Once the implant is ready, surgeons perform a second procedure. During this surgery, the surgeon carefully removes the damaged cartilage from the defect, creating a stable environment for the implant. The surgeon then precisely shapes the MACI membrane to fit the defect and secures it in place.

Because the implant is customized to the patient’s specific injury, it can provide excellent coverage of the damaged area. As healing progresses, the implanted cells begin producing new cartilage tissue.

Because the procedure uses the patient’s own cartilage cells, it provides a biologic approach to cartilage restoration. The treatment is specifically designed to fill cartilage defects with new cartilage-producing cells rather than simply covering the damaged area.

MACI can improve pain, reduce swelling, and restore knee function in patients with symptomatic cartilage defects. Many patients are able to return to recreational activities, sports, and active lifestyles following successful treatment.

MACI can help preserve the knee joint by addressing cartilage damage before it progresses to more extensive joint degeneration. For younger and active individuals, MACI may serve as an important joint-preservation strategy that helps delay or prevent the need for more invasive procedures in the future.