Matrix-induced Autologous Chondrocyte Implant

Written by Dr Sheila Strover on March 14, 2025

Matrix-induced autologous chondrocyte implantation - or MACI - is a technique of cartilage repair involving growing cells on a matrix. Page updated June 2024 by Dr Sheila Strover (Clinical Editor)

Cartilage defect being 'harvested'

A tiny bit of healthy cartilage is harvested from a non-weight-bearing part of the joint, and sent for culture. The massively increased number of active cells will be used to fill a defect in a weight-bearing area.

Illustration of the bones of a knee joint, where healthy cells from the edge of a cartilage defect are being harvested and sent to a laboratory.

Matrix-induced autologous chondrocyte implantation - what does it mean?

The name of this procedure is a real mouthful! This is what it all means -

  • matrix-induced - This is a two-stage procedure. The patient has one anaesthetic to remove a small piece of healthy joint cartilage from a relatively unimportant part of the knee. This is treated in a laboratory and the cartilage cells are extracted and allowed to multiply by being seeded onto a matrix.
  • autologous - This means that the original cartilage piece used for the procedure is taken from the patient him/herself
  • chondrocyte implantation - A chondrocyte is a cartilage cell, and it is the laboratory-multiplied cells that are placed back into the damaged area during a second anaesthetic.

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MACI is one of several cartilage repair options

Most cartilage repair procedures rely on living cartilage cells, which can be obtained via a number of methods -

  • from stem cells from the underlying bone via the procedure of microfracture
  • harvested and transplanted within a cartilage plug such as in the OATS procedure
  • multiplied in the laboratory and returned to the patient on a matrix which is glued into the original defect, such as in this MACI procedure.

In this clinical study...."AMIC performed better than mACI for chondral defects of the knee at ~40 months follow-up. The rate of complications was noticeably lower in the AMIC group."

Filippo Migliorini et al

Cartilage injuries in the knee are common and can occur in isolation or in combination with limb malalignment, meniscus, ligament, and bone deficiencies. Each of these problems must be addressed to achieve a successful outcome for any cartilage restoration procedure.

Aaron K Krych et al

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AMIC, Articular cartilage repair

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Forum discussions

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