Understanding Surgical Best Practices for MACI Knee Cartilage Repair Skip to content

Understanding Surgical Best Practices for MACI Knee Cartilage Repair

MACI knee cartilage repair is the third generation of autologous chondrocyte implantation (ACI), and it advances upon previous ACIs by offering surgeons a simpler, shorter and more versatile procedure to repair patients’ articular cartilage defects of the knee using an implant generated from their own cartilage cells (prior generations of ACI required a periosteum or collagen membrane cover).

Best practices in MACI surgery


MACI surgery can have multiple benefits including:

  • It can be implanted via mini arthrotomy.
  • The procedure is less invasive, with fewer steps than prior generations of ACIs, reducing operative time.
  • The MACI membrane can be custom trimmed to the size and shape of any defect in most areas of the knee.
  • A patient's characterized cells are distributed onto the MACI membrane in a density of 500,000 to 1,000,000 per cm2 using the proprietary Uniform Loading Unit (ULU) which allows for the application of a consistent dose of cells regardless of defect size.
  • The MACI membrane can be secured with fibrin sealant alone, but also permits the use of sutures or suture anchor fixation when needed.

To help you explore the features of the procedure, we gathered best practices for performing MACI to inform your surgical approach for MACI. The following practices do not constitute medical advice, and patients should be assessed according to their unique circumstances.


Step 1 – Preparing the Defect

The knee joint will be accessed via mini arthrotomy and assessed.

Next, to prepare the defect, the surgeon will take advantage of tools in the MACI implantation tray.  Create a uniform template of the knee cartilage defect with the MACI customer cutter. With the provided mallet, tap the MACI custom cutter down to the subchondral bone. Use the ring curette to debride the damaged cartilage, including the calcified layer, back to vertical walls of healthy cartilage. Hemostasis must be achieved prior to implantation using hemostatic agents.

Best Practice: When using the MACI custom cutters, allow 2-3 mm of cartilage to exist between the defect and the ring walls. When removing the defect, use the tools angled toward the center of the defect in case they slip.

Preparation of the Defect


Step 2 –Customizing the MACI Implant

Surgeons will customize each MACI membrane to fit the size and shape of each debrided knee cartilage defect.

Take the same custom cutter and mallet used to outline the cartilage defect and size the MACI implant to identically fit the template.

While surgeons do not have to use the custom cutters, the option to create templates using these tools makes MACI highly reproducible and provides a line to line fit.

Best Practice: The MACI implant has a rough and a smooth side. The cells are seeded on the rough side. The MACI implant should be cell-side up. Keep track of the notch in the lower left corner to denote the cell-side is facing up.

Shaping the MACI Implant


Step 3 - Placing the MACI Implant

Apply a thin layer of fibrin glue to the defect area. The implant should be implanted with the cell-side facing the subchondral bone (the cell-seeded side has a rougher texture). Additional fibrin sealant can be applied to the rim of the implant. Apply light digital pressure to the implant for three minutes. Suture fixation may be used to secure the implant if desired or conditions warrant.

Best Practice: Once the implant is secured, surgeons can gently place their thumb over it and hold pressure for 2-3 minutes. Cycle the knee 10-15 times to ensure MACI is securely adhered.

Placement of the MACI Implant


MACI Surgery Training and Development

If you are ready to introduce the MACI procedure to your patients with knee cartilage injuries, complete the MACI surgeon training at MACI University.

Note: the FDA requires MACI surgeon training before performing your first MACI procedure.

For additional training and education on the MACI procedure, download the Touch Surgery app simulation on the App Store or Google Play to start your training.


Please see below for full indication and ISI.

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MACI repairs knee cartilage using your patient’s own chondrocytes

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Watch live MACI case videos with notable orthopedic surgeons.

Indication and Important Safety Information

Important Safety Information

MACI is contraindicated in patients with a known history of hypersensitivity to gentamicin, other aminoglycosides, or products of porcine or bovine origin. MACI is also contraindicated for patients with severe osteoarthritis of the knee, inflammatory arthritis, inflammatory joint disease, or uncorrected congenital blood coagulation disorders. MACI is also not indicated for use in patients who have undergone prior knee surgery in the past 6 months, excluding surgery to procure a biopsy or a concomitant procedure to prepare the knee for a MACI implant.

MACI is contraindicated in patients who are unable to follow a physician-prescribed post-surgical rehabilitation program.

The safety of MACI in patients with malignancy in the area of cartilage biopsy or implant is unknown. Expansion of present malignant or dysplastic cells during the culturing process or implantation is possible.

Patients undergoing procedures associated with MACI are not routinely tested for transmissible infectious diseases. A cartilage biopsy and MACI implant may carry the risk of transmitting infectious diseases to healthcare providers handling the tissue. Universal precautions should be employed when handling the biopsy samples and the MACI product.

Final sterility test results are not available at the time of shipping. In the case of positive sterility results, health care provider(s) will be contacted.

To create a favorable environment for healing, concomitant pathologies that include meniscal pathology, cruciate ligament instability and joint misalignment, must be addressed prior to or concurrent with the implantation of MACI.

Local treatment guidelines regarding the use of thromboprophylaxis and antibiotic prophylaxis around orthopaedic surgery should be followed. Use in patients with local inflammations or active infections in the bone, joint, and surrounding soft tissue should be temporarily deferred until documented recovery.

The MACI implant is not recommended during pregnancy. For implantations post-pregnancy, the safety of breast feeding to infant has not been determined.

Use of MACI in pediatric patients (younger than 18 years of age) or patients over 65 years of age has not been established.

The most frequently occurring adverse reactions reported for MACI (≥5%) were arthralgia, tendonitis, back pain, joint swelling, and joint effusion.

Serious adverse reactions reported for MACI were arthralgia, cartilage injury, meniscus injury, treatment failure, and osteoarthritis.

Please see Full Prescribing Information for more information.


MACI® is an autologous cellularized scaffold product that is indicated for the repair of single or multiple symptomatic, full-thickness cartilage defects of the adult knee, with or without bone involvement.

MACI® (autologous cultured chondrocytes on porcine collagen membrane) is an autologous cellularized scaffold product that is indicated for the repair of single or multiple symptomatic, full-thickness cartilage defects of the adult knee, with or without bone involvement.

MACI is intended for autologous use and must only be administered to the patient for whom it was manufactured. The implantation of MACI is to be performed via an arthrotomy to the knee joint under sterile conditions.

The amount of MACI administered is dependent upon the size (surface in cm2) of the cartilage defect. The implantation membrane is trimmed by the treating surgeon to the size and shape of the defect, to ensure the damaged area is completely covered, and implanted cell-side down.

Limitations of Use

Effectiveness of MACI in joints other than the knee has not been established.

Safety and effectiveness of MACI in patients over the age of 55 years have not been established.