Preliminary But Exciting: Newer Kind of Autologous Chondrocyte Implantation Looks Good at Five Years

If this works out in Phase II trials, it will be nice to have one more option to call on in these tough situations

What’s the Claim?

It’s a race to see which we discover first — the fountain of youth or a biological solution for articular cartilage defects . . . though some aging weekend warriors would say those are more or less the same thing. Either way, place your bets.

The latest report from the chondrocyte front is a 5-year follow-up of a small but exciting randomized controlled trial that compared costal chondrocyte-derived pellet-type autologous chondrocyte implantation (ACI) to microfracture for articular cartilage defects of the knee. This newer type of ACI came out on top, with:

  • Dramatically better cartilage appearance on MRI (MOCART score of 62 ± 11 versus 27 ± 16 favoring the new type of ACI), and, perhaps as importantly, the MOCART scores did not worsen in the ACI group while they did in the microfracture group.
  • Better KOOS and Lysholm scores, by clinically important margins (391 ± 70 versus 303 ± 100 for KOOS and 85 ± 13 versus 65 ± 26 for Lysholm); there were no-difference findings on VAS pain and IKDC scores, but these were almost certainly because of the very small sample sizes. The “trends” all pointed in the same direction, favoring ACI.

This technique is still in Phase II trials in the USA, and so we consider these findings preliminary. Even if you're enthused about it, it may not be available to you yet, depending on where in the world you are.

How’s It Stack Up?

This is the follow-up study to a 1-year report on this same RCT, which is freely available in full-text form if you want to go deep. The trial was small (20 in the ACI group, 10 in the microfracture group) but very well designed, and nearly all the patients were accounted for at 5 years. Perhaps the most impressive finding was how good the lesions looked on MRI at 5 years in the ACI group. Of course, we don’t treat MRIs, we treat people, and so the findings on outcomes scores here were really important — and also supported the new approach.

A word about that approach, as it was new to me — the product is called CartiLife (Biosolution), and the authors describe it as “a small pellet-type ACI product that is manufactured from chondrocytes from a patient’s own costal cartilage, followed by expansion culture and 3-dimensional pellet culture.”

At first blush, I thought that perhaps microfracture was a bit of an unfair comparator in the sense that it’s not a consistent intervention, but a 6-year old systematic review evaluated the Level-I and Level-II evidence of ACI versus microfracture and actually concluded that ACI was no better than microfracture. This reassured me that it is a fair comparator in this setting.

Interestingly, a more-recent systematic review focused on so-called third-generation ACI — which included only one more study and did not include the 1-year RCT report on the patients we're discussing here — favored ACI. The needle may be moving in that direction.

What’s Our Take?

We do not recommend you change your practice based on an RCT of 30 patients. It’s more that these patients often don’t have great options, their pain levels can be severe, and their loss of cherished activities substantial. If this new approach does well in Phase II trials, it will be nice to see how it does "out in the real world."


Yoon KH, Lee J, Park JY. Costal Chondrocyte-derived Pellet-type Autologous Chondrocyte Implantation Versus Microfracture for the Treatment of Articular Cartilage Defects: A 5-Year Follow-up of a Prospective Randomized Trial. Am J Sports Med. 2024;52:362-367.