The MACI Procedure
Individuals suffering from articular cartilage lesions within the knee may qualify for a Matrix-Induced Autologous Chondrocyte Implantation surgery, or MACI procedure opposed to microfracture repair. To perform a MACI procedure, an orthopedic knee specialist harvests cartilage cells from the knee of the patient. The surgeon sends the harvested cartilage cells to a lab where the cells grow into additional cartilage. Once regenerated, the surgeon implants the new cartilage into the damaged area of the knee. The body absorps the new cartilage and fills the defect within the knee.
Candidates for a MACI Procedure
A Matrix-Induced Autologous Chondrocyte Implantation surgery repairs cartilage defects and damaged cartilage within the knee. Surgeons may perform a MACI procedure in different areas of the knee including:
- The Lateral Femoral Condyle
- The Medial Femoral Condyle
- The Patella (kneecap)
- The Trochlea
Collecting and regrowing the healthy cartilage
A Matrix-Induced Autologous Chondrocyte Implantation procedure starts with the treating physician taking a biopsy of cartilage from the patients knee. Many experienced knee surgeons prefer to take the biopsy from the intercondylar notch or the proximal medial or lateral condyle. Many surgeons choose these harvest sites due to them not being a large part of weight-bearing in the knee. Once harvested, the surgeon sends the cartilage biopsy to a lab. At the lab, specialists extract cartilage cells from the cartilage. Cartilage cells, or chondrocytes, produce and maintain the cartilaginous matrix. The lab takes the chondrocytes and places them onto a collagen membrane that can absorb them, allowing them to regenerate and grow into additional healthy cartilage
How surgeons perform a MACI procedure
Once the patient decides to undergo the transplantation surgery, the lab sends the cartilage to the hospital or surgical center where the surgeon performs the MACI procedure. The lab sends the cartilage in an aseptic state but not sterile. If something occurs and the patient can no longer undergo the procedure but the lab has already sent the cartilage, the surgeon must take a new biopsy and restart the process.
To start the cartilage transplant, the surgeon cuts the damaged portion of the cartilage and removes it. Using the same cutter and mallet used to remove the damaged cartilage, the surgeon then cuts into the new regenerated cartilage. Using the same tools allows the surgeon to create a piece of cartilage with the exact same shape and dimensions of the removed damaged cartilage. Using a sealant, the surgeon secures the new cartilage implant.
Recovering from a MACI procedure
Following a Matrix-Induced Autologous Chondrocyte Implantation surgery, the recovery depends on the size and location of the cartilage lesion. Larger areas of cartilage damage require longer healing time. Cartilage damage in areas of the knee that play a large role in weight bearing may also require more time to heal. In most cases, patients must use a brace and crutches for at least 6 weeks following a MACI procedure. Bearing weight on the surgical leg too soon may delay healing or injure the graft. Typically patients begin a rehabilitation physical therapy program a week following surgery which involves passive movements and isometric exercises to restore range of motion and reduce post-surgical muscle atrophy. The rehabilitation process happens in phases and patients should always follow the protocol given to them from their knee surgeon. Each surgeon has their own protocol based on experience and education so patients should always listen to their specific treating physician.
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