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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 during which 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 to be cultured and grown to a large volume of cells, 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 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. 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, but many patients do. Patients who have demonstrated joint space narrowing on x-ray or who have been told they have “bone on bone” osteoarthritis may not be a suitable candidate for MACI.


The first step of your surgical management is a day 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 5mm wide X 10mm 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 in Cambridge, Massachusetts to be cultured and grown to a large volume of cells and grown on a collagen membrane to be used for the second step of your surgery. Your arthroscopy will be done using general anesthesia and will take approximately 25 minutes. You will go home the same day of your surgery. You will be given crutches to use following your arthroscopy for 2-3 days. You will be permitted to put full body weight on your leg immediately following surgery but it is a good idea to use crutches to help support you as you will be somewhat sore in the first few days following this procedure. When you return to the office for your post-operative appointment, you will meet with your surgeon and his nurse practitioner to discuss the findings of your arthroscopy. This is the appointment during which the final plan for your MACI will be made.

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The second step of your surgical management is the MACI procedure. This procedure is done as an open procedure, which means you will have a larger incision which will measure anywhere between 3-6 inches in length. During this step in your surgical management your surgeon will open your joint through an incision to locate the areas of damage. Once these areas have been located they will be debrided or cleaned out in preparation for the implantation of your new laboratory grown cells. Once the areas of damage have been cleaned 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 graft(s) (is)/ are then carefully placed into your defects or “potholes”, where they are glued into place with possible supplemental sutures to make them secure. Once all of the “potholes” have been treated your incision will then be closed using “dissolvable stitches”. Depending on the number of “potholes” and their size within your joint,this surgical procedure will take between one and three hours. This procedure will be done using either general anesthesia or spinal anesthesia depending on your preference. At the end of the surgery, Dr. Minas will inject a long acting combination of medications into the tissues to minimize your discomfort when the anesthesia wears off. The medications usually relieve pain for 12-24 hours.

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WK 0-6

Femoral Condyle 

WK 7-12

WK 13+

Patella and/or Trochlea

Femoral Condyle + TTO

Femoral Condyle + Patella and/or Trochlea

Patella and/or Trochlea with HTO & TTO

Patella and/or Trochlea with DFO & TTO


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