You may be referring to autologous chondrocyte implantation (ACI). Autologous chondrocyte implantation refers to using the patient’s own cartilage to repair deep holes or defects in the cartilage. These type of full-thickness, large lesions of the knee occur most often in in active, high-demand patients such as athletes.
If you’ve already had surgery for this problem, you’ve probably had a debridement or microfracture procedure. Debridement removes any loose fragments and smoothes the cartilage surface of the joint. Microfracture is the drilling of tiny holes through the cartilage to the joint surface. This technique stimulates bleeding and sets up a healing response. Debridement and microfracture are considered first-line treatment approaches.
A third treatment option for first-line care of cartilage injuries is an osteochondral autograft transplantation. This involves harvesting a layer of cartilage and bone from a healthy area of the same patient’s joint and transferring it to fill in the hole. Any of these first-line treatment approaches work well for inactive or low-demand patients with small lesions. But for active patients with large defects, a different procedure might work better. That’s the autologous chondrocyte implantation (ACI).
To perform an ACI, the surgeon first removes healthy cartilage cells from the patient and sends them to a special lab where they grow more of the same type of cells. When there are enough cells to fill the hole, the surgeon performs the second part of the procedure. The hole is prepped for the new cells, which are then placed in and around the defect. The implanted area is then covered over with a patch of periosteum, the outer layer of bone (also harvested from the patient). The patch fits over the repaired defect like a manhole cover.
There are some potential problems with this treatment method. Removing cartilage cells and periosteum needed for the implantation always leaves the donor site at risk for subsequent problems. And the implanted chondrocytes don’t always fill in with good, solid cartilage. Sometimes, the new growth is just a fibrous type of cartilage. But there are some long-term studies that show it holds up for the majority of patients who say they would have the same treatment again.
Properly selected patients can expect the good results to last for many years as shown by this study. Patients older than 40 are less likely to have chondrocytes with active growth factors and more likely to have fewer new, healthy cartilage cells form.