Matrix Associated Chondrocyte Implantation (MACI)

By Carlos Tandron, MD

Overview of Knee

Your knee is a complex joint where three major bones come together: the shin bone (tibia), the thigh bone (femur), and the knee cap (patella). Ligaments and cartilage connect and protect these bones at the knee joint.

Cartilage is a strong, rubbery, and key connective tissue found in many parts of the body, including joints. The two types of cartilage found in the knee are the meniscus, which acts as a cushion between the femur and the tibia, and the articular cartilage which covers the ends of the bones to ensure smooth movement.

knee pain

Image of Knee Pain

This articular cartilage can be damaged many ways. Chronic or repetitive actions from exercise, sports, or physical work can cause articular cartilage to weaken and wear out with time.  Acute or traumatic events such as a fall, or a forceful twist or a sports injury can also cause immediate and severe cartilage damage and create hole or roughening to the smooth surface, known as an articular cartilage defect.  Symptoms of articular cartilage defects can include pain, swelling, clicking and locking.

Unfortunately, cartilage does not heal on its own. Unlike other body tissues, cartilage does not repair itself. Cartilage injuries are chronic and often get worse as time goes on. If conservative treatment has not worked to relieve pain, surgery is often the next step.

Traditional Surgical Treatment Options for Damaged Knee Cartilage:

  • Chondroplasty
    • Also called debridement and lavage. Damaged cartilage is trimmed off, and then the area is cleansed with sterile water. Chondroplasty may offer temporary relief but does not repair the cartilage.
  • Marrow Stimulation
    • Such as microfracture, abrasion arthroplasty, and subchondral drilling. Small holes are drilled into the bone allowing blood and bone marrow cells to seep out creating a blood clot that forms repair tissue. The surgical techniques form a tissue that is closer to fibrocartilage rather than the more durable hyaline cartilage found in normal articular cartilage.
  • Osteochondral Implants
    • Autologous or Allograft. Healthy pieces of both cartilage and bone are placed into damaged areas, using a patient’s own tissue (osteochondral autograft, also called OATS®) or tissue from a cadaver (osteochondral allograft).
  • Autologous Chondrocyte Implantation (ACI)
    • A biologic procedure uses a patient’s own cartilage cells in a lab to grow additional cells, which are implanted in the damaged area. The new tissue has properties similar to hyaline cartilage, the durable tissue found in articular cartilage.

Used for more than 20 years, ACI has been proven to provide long-lasting pain relief and to help patients regain knee function. The newly adopted MACI® procedure is a third generation ACI, offering a safer way to deliver cells to the damaged area of cartilage.

MACI (autologous cultured chondrocytes on porcine collagen membrane) is a procedure that repairs cartilage using the patient’s own cells. They are grown in a laboratory and placed onto film which is implanted into the area where the damaged cartilage was located, providing long-lasting pain relief and improvement in function.

Here’s How the MACI Process Works

Once Dr. Tandron decides that surgical intervention is necessary, a knee arthroscopy will be performed to assess the cartilage damage in the knee.  If he thinks that MACI may be an option for you, Dr. Tandron will take a biopsy (a sample of tissue approximately the size of two Tic Tacs) of your healthy knee cartilage. The biopsy is shipped to a state of the art, FDA licensed cell processing facility in Cambridge MA, where it will be cryogenically stored. In a proprietary process, cartilage cells are expanded and uniformly seeded onto a resorbable collagen membrane.  The MCAI implant is delivered to the operating room on the day of your surgery and will be shaped by your physician to the size and shape of your cartilage defect.  This implant will be placed onto your knee and affixed to the damaged area. Over time, the implanted cartilage cells will continue to grow and solidify covering and filling the affected area leaving the patient with a new cartilage surface.

Rehabilitation Timeline Following a MACI Procedure

Following the MACI procedure, your knee will be immobilized and you will need to follow a physician-prescribed rehabilitation program specifically designed for you. Consult with Dr. Tandron and physical therapist to determine when you might be able to drive and return to work or other activities.

A support program is available to assist with a smooth recovery. The commitment you make to the rehabilitation program will play a key role in your return to activity. Recovery time varies greatly as no two patients are alike but most can expect to resume normal daily activities in 3-6 months, recreational activities in 6-9 months, with full return to normal function in 9-12 months.

MACI has been shown in research studies to provide three important things:

  • A functional repair tissue
    • MACI produces a type of repair tissue that alleviates symptoms and restores joint function which has been shown to form as early as 6 months after the MACI procedure.1
  • Reduced pain and improved function
    • In the SUMMIT clinical trial, MACI has been shown to offer greater pain relief and improvement in function when compared to microfracture.1
  • Patient satisfaction
    • In the SUMMIT clinical trial, MACI patients reported higher quality of life scores, a greater ability to perform recreational and sports activities, and improved overall knee function.1

The safety and long-term clinical benefit of MACI have only been studied in the knee joint. MACI has not been approved for use in joints other than the knee. The safety and effectiveness of MACI have not been proven for patients 55 years old and older.

  1. Saris D, Price A, Widuchowski W, et al. Matrix-applied characterized autologous cultured chondrocytes versus microfracture: Two-year follow-up of a prospective randomized trial. Am J Sports Med. 2014;42(6):1384-94.

If you would like to discuss this exciting new option for cartilage repair please use the link below to set up a consultation with Dr. Carlos Tandron by calling JOI-2000 or clicking on the image below to request an appointment.

carlos tandron, MD

Image of Dr. Carlos Tandron


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