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Knee Operations and Procedures

Subject

Overview and important principles

The MACI procedure (Matrix-induced Autologous Chondrocyte Implantation) is a technique to repair areas of damage to articular cartilage - the normally smooth bearing surface in the knee joint.

Once damaged, articular cartilage normally does not heal itself, and the MACI technique involves repairing the surface with a synthetic membrane seeded with a patient’s own cells. This is fixed in place using fibrin glue and the cells are then able to produce, over time, a new layer of smooth articular cartilage surface.

Two operations are required for this procedure. The first is an arthroscopic day case procedure to take a small area of healthy articular cartilage surface. Articular cartilage cells (chondrocytes) from this sample are cultured in the laboratory and seeded on to a membrane. This is then implanted 6 – 8 weeks later at a second procedure which involves an open operation on the knee joint.

Rather like a new patch of turf this delicate area needs time to fully mature before being subjected to the vigorous impact loads in sport, and therefore the rehabilitation is deliberately slow and restrictive.

The key to success is an understanding of the principles of the way the joint surface heals and matures and this requires knowledge by the treating physiotherapist and rehabilitation expert PLUS buy-in by the patient, who needs to understand what is good and bad for the new joint surface.

Going back to the new turf analogy, it is perfectly possible to immediately walk on a new patch of turf and it may not seem to cause harm, but 6 months later the area that was killed off or dented by the inappropriate weight and shearing force will be painfully clear to see.

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