Matrix Autologous Chondrocyte Implantation (Maci)

Matrix Autologous Chondrocyte Implantation (Maci)


Matrix Autologous Chondrocyte Implantation (MACI) is a surgical procedure for the treatment of painful full thickness cartilage defects in the knee. MACI is a two-part surgical procedure. The first surgical procedure is an arthroscopic procedure. At the time of the arthroscopy, a thorough evaluation of the joint is made, and a biopsy of cartilage is taken for cell culture and cryopreservation. This biopsy is sent to Vericel, a Cambridge, Massachusetts-based cell therapy company, where the cartilage cells are cultured and grown to a large volume, frozen in liquid nitrogen, and stored for up to 2 years. After insurance approval for treatment, an elective surgical date is chosen for the second stage. The second surgical procedure is an open procedure during which the cultured cells that are seeded on a collagen membrane (MACI) and then re-implanted into the area(s) of damage within the knee joint.


MACI is designed for the treatment of isolated cartilage defects in symptomatic young active patients. These isolated cartilage defects are often referred to as ‘potholes,’ as they tend to resemble potholes in a street. Patients who have demonstrate joint space narrowing on x-ray or who have been told they have “bone-on-bone” osteoarthritis may not be suitable candidates for MACI.

MACI allows patients to return to pain-free activities of daily living, such as walking, stair climbing, and cycling. MACI is not predictable in allowing patients to return to high-level sports competition, such as long distance running and competitive team sports.


The first step of your surgical management is an outpatient surgical arthroscopy. This means that your surgeon will use a camera and two or three small 1/4-inch portholes to examine the inside of your joint. Several photos will be taken inside your joint to document the areas of damage. During this procedure, your surgeon will also take a small piece of cartilage from a non-weight bearing area of your joint about 5-mm wide ×10-mm long (the size of a thumbnail clipping or 3 ‘tic-tacs’). This small piece is called a cartilage biopsy. This biopsy will be sent to Vericel to be cultured and grown to a large volume of cells and seeded on a collagen membrane to be used for the second stage surgery.

Your arthroscopy will be done using general anesthesia and will take approximately 30 minutes. You will go home the same day of your surgery. You will be given crutches to use following your arthroscopy. You will be permitted to put full body weight on your leg immediately following surgery. However, it is a good idea to use crutches for support, as you will be sore the first few days following this surgery.

When you return to the office for your post-operative appointment, you will meet with your surgeon to discuss the findings of your arthroscopy. This is the appointment during which the final plan for your MACI will be made.


The second stage surgery is the MACI (matrix autologous chondrocyte implantation) procedure. This procedure is done as an open procedure, which means that you will have a larger incision, measuring anywhere between 3-6 inches in length. During this surgery, your surgeon will open your joint through an incision to locate the areas of damage. Once these areas have been identified, the damaged cartilage will be debrided (or ‘removed’) in preparation for the implantation of your new laboratory grown cells. Once the areas of damage are debrided and are ready to accept the new cells, your surgeon will cut the MACI membrane precisely to fit the prepared damaged area. The MACI implant(s) (is)/ are then carefully placed into your defects or ‘potholes,’ where they are glued into place with possible supplemental sutures to secure them. Once all of the “potholes” have been treated, your incision will then be closed using ‘dissolvable stitches.’ Depending on the number of cartilage “potholes” and their size(s), this surgical procedure will take between 1-3 hours. This procedure will be done using either general anesthesia or spinal anesthesia, depending on your preference. At the end of the surgery, your surgeon will inject a long-acting combination of medications into the tissues that are operated upon to minimize your discomfort when the anesthesia wears off. The medications usually relieve pain for 12-24 hours.


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