Articular Cartilage (Chondral) Lesions

Autologus Chondrocyte Implantation (ACI) and
Matrix associated Autologous Chondrocyte Implantation (MACI)

ACI is a method which can be used to treat cartilage defects in the knee, and involves 2 operations:

In the first operation, key hole surgery is used to harvest cartilage from the injured knee. These cells are then used to grow many more cells in the laboratory. It usually takes 6 weeks for the cells to multiply sufficiently and, at this stage, the second operation is performed. This procedure involves either another keyhole surgery operation if the lesion being treated is suitable or if the lesion is too large then a cut on the front of your knee, and the cells grown in the laboratory are replaced at the injury site. A membrane was used to keep the cells in the correct location.

The technique has developed over the last twenty years. In first generation techniques a membrane was taken from the lining of your own bone (periosteum), there was a high rate of this lining overgrowing and needing a further operation to thin that overgrowth down. This led to the development of the second generation of the technique using a membrane manufactured from porcine collagen (pig connective tissue) in the laboratory. There was a reduction in the need for the third operation, but as the membrane was being sutured in place it required a very wide exposure through a long cut at the front of the knee. Third generation techniques have allowed the cut to be made much smaller by using a “glue” called fibrin sealant to attach the cells which are now actually seeded into a porcine membrane in the laboratory. The latest development of this technology has been the insertion and fixation of this “MACI” (Matrix associated Autologous Chondrocyte Implantation, Genzyme Therapeutics, Oxford. UK) implant using keyhole surgery. This has enabled the operation to be much less painful and quicker to get over. There is a long period of modified activity required to allow the cells to multiply and establish a new lining of the knee.

The following images demonstrate the development of ACI treatment for a cartilage injury:

The chondral defect is debrided to remove all unstable cartilage.

Close examination of the trimmed chondral defect reveals evidence of the previous unsuccessful microfracture.

First generation technique:

The periosteal membrane is harvested and then sutured to the edges of the chondral defect.

Second generation technique:

Stitching the patch is completed.

This image illustrates a periosteal patch, but a porcine origin membrane would be used in an identical manner.

The sutured patch is now sealed with fibrin glue

Once sealed the patch is tested for water-tightness and the patient’s own cells are injected beneath it.

Third generation technique:

The porcine membrane with the patient’s own cells implanted in its deep surface being cut to fit the defect perfectly.

By using fibrin sealant instead of suturing, although this is a larger cartilage defect it has been repaired with using a much smaller approach.

Arthroscopic technique:

It is now possible for some cartilage defects to insert and fix the membrane by keyhole surgery.

A cartilage defect on the medial femoral condyle after removing a failed microfracture showing a central osteophyte (bony bump).

The MACI membrane fixed in place with fibrin sealant arthroscopically, after the central osteophyte had been removed.

Arthroscopic appearance of a MACI graft at four months

Further information is available at:
ACTIVE Trial (additional reading) and SUMMIT Trial (additional reading)

For patient information following a Microfracture


This leaflet has been devised to act as a guide to you, of what to expect following your operation

During surgery multiple small holes are made in the bone at the bottom of the cartilage defect.
This causes bleeding and a clot is formed in the hole. This clot enables new cells to form a repair cartilage that fills the gap.

After surgery it is important to protect this clot so that new cells can form. This is done by limiting weight bearing. You are allowed to place your foot on the floor, but not to take much weight through the leg for 6-8 weeks, depending on the size of the area involved.
Return to function and sporting activities can vary between individuals but most people notice
significant improvement 6 months after surgery, although full recovery can take up to 2 years.

If this technique is used on the patella you will be put in a knee brace, which restricts your range of movement when walking. You will be able to take weight through the leg as long as it is comfortable.

It is very important (after the operation) to regain full range of movement of both knee bending and straightening. To help achieve this, you will stay in hospital overnight and a machine will help to move the knee for you whilst you are recovering.

If you need further advice please contact the McNicholas Knee Clinic and arrange a consultation is part of the Premier Surgeons Group ©2007. Disclaimer l l l l