Matrix-induced chondrocyte implantation (MACI) at Nuffield Health at St Bartholomew's Hospital

Articulating cartilage is the tissue covering the ends of joint surfaces. Healthy articulating cartilage allows the joint to move smoothly. Damage or injury to cartilage can cause pain, swelling, knee locking (joint is stuck in one position) or the knee can give way. Damage can often lead to osteoarthritis later.

When conservative treatments such as knee arthroscopy are not successful your consultant may recommend surgery, depending on the exact situation in your knee.

What happens during MACI?

Matrix-induced chondrocyte implantation is a two-step procedure. During the first procedure your surgeon will take a small sample of healthy articular surface from the good part of your knee using arthroscopy. The sample is processed and the key cells (chondrocytes) are grown and seeded on a membrane ready for later implantation.  Most patients go home the same day.

After 6-8 weeks your surgeon will perform an open operation to remove the damaged cartilage from your knee and replace it with the membrane containing the healthy cells. The typical incision from this procedure is about 5-10 cm. The wound will be closed with stitches or staples. You may stay 1-2 nights in hospital.

Recovery from your MACI procedure requires a very disciplined approach. A physiotherapist will visit you to show you how to care for your wound and give you exercises to help you get mobile.

After MACI

It is important that you follow your recovery and rehabilitation instructions carefully. This will include specific instructions on the stages of weight bearing and range of motion. It takes a long time for the new area of repaired surface to grow and mature enough to take the high loads imposed on the knee and it is important to avoid overloading the delicate surface during that time.

Initially you will need to use crutches for at least the first 6 weeks. You may also have a brace on your knee to protect the implant area. Ice and elevate your operative leg regularly to reduce any swelling.

You will need to return to hospital for a follow-up visit about 2 weeks after your implant procedure.

To allow full recovery of your new cartilage surface you should avoid any strenuous activity or impact sport for at least 12 months. Most patients are released to drive after 6 weeks.

Be sure and discuss any return to work with your consultant.

The MACI procedure is not for everyone. Your consultant will need to assess several aspects of your condition before recommending this treatment. The area of damage in your knee needs to be exactly suitable for this type of repair.