We just got the results back from our son’s knee surgery. He had a surgery done called ACI in which they took some of his own knee cartilage and used it to fill a couple little holes in his knee joint. The report says the holes have filled in but not with normal tissue. Looks like mostly random fibers, not true cartilage. He’s not having any pain so does it matter? And will it eventually turn into the real stuff?

These are all very good questions that remain under investigation. You didn’t mention your son’s age but we know from a recent study done in England that this particular surgery is being used more often now in adolescents.

This approach called autologous chondrocyte implantation or ACI is quite successful in adults and rising in use among younger patients. Autologous tells us the graft was taken from the patient. A donor sample of chondrocytes comes from a non-weight-bearing section of the knee.

The cells are taken to a lab where they are grown into a larger donor patch of articular cartilage cells. This can take anywhere from four to six weeks. When there are enough lab-grown chondrocytes, the patient comes back in for part two of the surgical procedure.

In this operation, the damaged cartilage is cleaned out and the edges are shaved smooth in preparation for the graft material. The hole is filled in with donor chondrocytes and covered with a special membrane that is stitched in place, sealed, and watertight.

The number of cases of osteochondral injury in young athletes continues to rise. “Osteo” refers to bone, whereas “chondral” directs our attention to cartilage. So, the osteochondral layer is the cartilage next to the first layer of bone in the knee joint.

The increase in this type of injury is because active individuals end up with more traumatic injuries (e.g., direct blow to the knee) or repetitive minor trauma than other less active adolescents and/or adults.

When researchers go back years after the repair and take a look at the repaired site, here’s what they find. A large number of patients (84 per cent in the study from England) have excellent results regardless of the size of their lesion (large or small).

Pain is routinely less and both motion and function are improved. Of particular interest is the condition of the graft site later. Slightly more than half the English group (57 per cent) had a patch of fibrous cartilage fill in the defect.

Only one-fourth of the group (about 24 per cent) formed the desired hyaline cartilage. A smaller number of patients (19 per cent) formed a mixture of fibers and hyaline cartilage. Only one patient had a failed result requiring additional surgery. These statistics are actually quite similar to the results reported for other (smaller) studies investigating the same things.

There is some evidence that the transplanted tissue actually continues to form new cartilage even after a couple of years. So there is hope that this procedure will prove to have good long-term results as well. More studies are needed to know the final result for sure — but it looks very favorable. Time will tell!