I’m looking into the various ways holes in the knee cartilage can be repaired. My surgeon recommended something called ACI for me even though I’m considered over the age limit for this surgery. Why are older adults less likely to be considered for these procedures?

Autologous chondrocyte implantation (ACI) is done when there are full-thickness defects in the articular surface of the joint. Essentially, there has been an injury that has pulled off a piece of the layer of cartilage that lines the joint. Full-thickness means the defect goes all the way down to the first layer of bone.

Autologous means the cells harvested for the implantation come from the patient who needs the repair. In other words, you donate your own chondrocytes (cartilage cells). A short surgery is scheduled to allow the surgeon to take a few chondrocytes from inside the knee cartilage. These cells are grown in a laboratory.

At a later date, the patient returns for a second surgery, during which the surgeon implants the newly grown cartilage into the lesion and covers it with a small flap of tissue. The cover holds the cells in place while they attach themselves to the surrounding cartilage and begin to heal.

The procedure has not been recommended for older adults because of changes in the way tissues heal later in life. In the case of cartilage defects, there has been some question about whether aging chondrocytes can really repair themselves. The combination of degenerative changes in the older joint along with decreased growth factor has kept surgeons from using autologous chondrocyte implantation with older adults.

The results of a recent study from Germany may change all that. In that study, the use of autologous chondrocyte implantation (ACI) for cartilage defects of the knee was compared for patients under age 40 to patients over age 40.

Comparisons were made between the two groups by matching patients’ age, defect size, and defect location. The results showed similar improvements in all areas for both groups. Follow-up was for a two-year period of time.

The authors suggest these results bring into question the need for such a strict age limit on this procedure. Of course, longer follow-up is needed to see what happens over time. Extending the age limit up to 50 or 60 years old for autologous chondrocyte implantation may be possible for adults with minimal signs of joint degeneration.