MACI – Articular Cartilage Restoration
An exciting new development in the treatment of articular (joint) cartilage termed MACI (membrane articular cartilage implantation) is now available for those patients with symptomatic or painful, focal loss of articular cartilage. Articular cartilage is the smooth, white ‘tread’ layer that surfaces the ends of the bone in joints throughout the body. Its primary function is to provide a gliding surface and cushion compressive forces that result from loads applied to the joint. Unfortunately, unlike many tissues that have the ability to heal themselves (like bone), the resilient weight-bearing cartilage tissue, if damaged, has a limited ability to repair itself. Cartilage cells (chondrocytes) don’t replicate (generate an abundance of new cartilage cells) as part of a reparative process. However, techniques to culture or grow cartilage cells in the lab have been developed over the past 2 decades. To restore a healthy joint surface, a sample (biopsy) of the patient’s own cartilage is obtained during an outpatient arthroscopic surgery. The live cartilage cells are isolated and cultured or multiplied in a sterile environment to produce millions of cells identical to the patient’s chondrocytes. Traditionally, at a second open surgery, the bone at the base of the defect was cleaned of any debris and any bleeding points sealed. A thin segment of tissue that surrounds bone (periosteum) or a collagen membrane was sewn around the defect to create a water-tight closure using very fine sutures. The suture line was sealed with tissue glue. The millions of cultured cells were then introduced into the defect and would begin to generate cartilage matrix (the resilient tissue that cushions the joint). Suturing a tissue lid over the defect was laborious, time-consuming, and could lead to an uneven distribution of cartilage cell throughout the defect.
MACI (membrane autologous chondrocyte implantation) was recently released by the FDA (Feb., 2017). The same process involving a cartilage biopsy and culturing of the patient’s own cartilage cells takes place. The autologous (obtained from your own body) chondrocytes are then impregnated onto a collagen membrane (something similar to fruit leather strip) in which the cells are distributed in a uniform fashion. At a second surgery which is open, a template is made of the cartilage defect. The collagen membrane with cells is shaped to perfectly match the template. It is then secured into the defect with a biologic ‘glue’. As the carrier membrane slowly dissolves, the delivered chondrocytes begin to generate new cartilage matrix, which will eventually provide the appropriate joint surface and cushion. Depending on the location of the cartilage defect (most commonly studied in the knee), approximately 85% good and excellent results have been obtained.
The healing process is prolonged and generally requires 9 – 12 months before vigorous loading activity is permitted. Partial weight-bearing is necessary for the first 8 weeks following surgery. The use of a CPM (continuous passive motion) machine assists in the formation and restoration of a uniform joint surface. MACI offers a long term biologic solution to resolve pain and restore function for those patients whose suffering is related to localized joint cartilage defects.
Full-thickness Cartilage Defect Foil Template MACI Implanted