Saturday, July 9, 2011

Microfracture vs. ACI: Which Makes More Sense?

If you must have knee surgery, which is better when you're missing a patch of cartilage: a microfracture or ACI (autologous chondrocyte implantation)?
With a microfracture, a surgeon pricks the bare, cartilage-less bone to create small holes, through which blood and bone marrow seep, forming a clot that releases cells that create cartilage. With autologous chondrocyte implantation, such as Carticel, your own cartilage (autologous) is basically grown in a petri dish, and the mature tissue (which has cartilage-producing cells, or chrondrocytes) is implanted in your knee.
The big knock against a microfracture: the cartilage produced isn't the good, mature variety, but rather a rubbery sort that's less durable (called "fibrocartilage").
ACI is the new, sexy, cutting-edge procedure. So if I had a choice, I would have a …
Here are six reasons why:
1. The surgery is less invasive. ACI involves an operation that peels the knee wide open. Unfortunately, extensive surgery may entail a higher risk of something going wrong/side effects.
2. The cost is cheaper. It appears that the microfracture is a fourth or fifth the cost of an ACI.
3. The procedure is more "natural." The microfracture spurs the bone to form replacement cartilage on its own. The ACI requires cartilage to be grown in a laboratory, then inserted into your knee.
4. 100 NBA players can't be wrong. Okay, it's not a hundred -- more like a dozen or so -- yet the point holds. Professional basketball players make multimillion-dollar salaries. They are attended to by the finest trainers and doctors. They can afford any kind of surgery.
When was the last time you heard of an active player undergoing an ACI instead of a microfracture? Granted, the microfracture doesn't always succeed. Still, players such as Jason Kidd, John Stockton and Amar'e Stoudemire have regained their old form after the operation.
Today, Stoudemire is renowned for his athleticism and leaping ability. He's an all-star, pounding up and down the court for the New York Knicks in what may be the most demanding sport for knee joints. That he has maintained his skills, post-surgery, while putting his knees under such stress, shows microfracture can be effective.
(Update: As is obvious to anyone who follows the NBA, I might have chosen a better example here than Stoudemire, who had knee surgery again during the 2012-2013 NBA season. Oh well. Basketball is a very hard sport on the knee joints.) 
That leads us to my fifth reason …
5. This study
Which dispels the belief that the only cartilage you get with a microfracture is inferior fibrocartilage. (That never made sense to me anyway: how could NBA players compete in such an intense game if their replacement tissue was solely fibrocartilage?)
In a study published in Arthroscopy in April 2006, researchers who took biopsies to inspect the cartilage that was formed after a microfracture observed (my bold):
This healed tissue is a combination, or hybrid, of fibrocartilage and hyaline-like cartilage [note: that's hyaline articular cartilage, the good stuff]
What's more, they examined the tissue after only a year, leading me to wonder -- had they done a biopsy after two, three or four years, might they have discovered an even higher proportion of hyaline cartilage compared to fibrocartilage?
Why do I wonder this? Well, when Robert Salter did his famous continuous passive motion experiment involving rabbits 30 years ago (the animals had small holes drilled in their knee cartilage to simulate defects), he found a few curious things (besides the banner news that motion, of the continuous and passive variety, is great for knees post-surgery).
One was this: The cartilage that grew back to fill the holes was at first immature, then gradually took on the characteristics of mature cartilage, complete with chondrocytes.
6. And this study too

For the study, 33 patients had a microfracture and 34 the ACI procedure. Then, at various times over the next two years, the condition of their repaired knees was assessed. Their ability to do one-leg hops was measured. Also knee mobility and strength were checked.
The researchers expected to find the ACI patients with a decided advantage over the microfracture group after two years. But this is what they discovered instead:
The most important finding of the present study was that the functional recovery at 2 years is comparable for both groups. The results show no superiority of ACI over microfracture at 2 years.
What's more:
More patients in the microfracture group recovered overall functional performance at 9 and 12 months.
Okay, that's why I'd prefer a microfracture over ACI. What about you?


  1. I'm still hoping to avoid surgery, but if I have to do it down the road... is microfracture something that helps chondromalacia? Hmmm, maybe I'll google that.--Jenni

  2. I doubt microfracture would be any doc's choice for anything but severe chondromalacia, where the tissue has worn away significantly. I should have made clearer at the outset: I'm not a big fan of surgery -- not at all -- so this post is more a "What would I choose if I HAD to choose?" My real preference would be neither, obviously!

  3. you can try AMIC surgery which is like a combination of both

  4. NBA Players don't often do ACI because of the recovery time...its takes about 1-2 years before you can do heavy acivity. With a microfracture, its about 6-8 months. Owners don't like to pay millions of dollars to a player on the side line. Ever heard of Greg Oden? He's had 3 microfractures becasue they fail after very few years if you are putting stess on it. The OATS proceure seems to be the best. Research that one.

  5. Yes, I'm quite aware of Greg Oden (which is why I noted above that microfractures don't always succeed). For every NBA player who has come back and had a good career after a microfracture, you can find someone who hasn't. And yes, I know the microfracture recovery is a lot shorter. (Personally, I think players rehab too hard and come back too fast after a microfracture, which is why the procedure isn't more successful -- just a theory. 6 to 8 months strikes me as much too short a recovery period, considering the intensity of NBA basketball.)

    One note: players are not mere chattel of the team owners, to be operated upon as the owners see fit. If someone said to a player, "You have an 80 percent chance of healing totally with an ACI, but only 40% with a microfracture, except with the ACI you'll be out an extra year or so" -- I bet some would opt for the ACI. I just don't think the ACI is that superior (if superior at all). See studies cited above.

    There are some threads on the Knee Guru site where people talk about the OATS procedure; if anyone's interested in undergoing it, that's where I'd start gathering information.

  6. I think superior to either of the options is stem cell paste grafting. It's practiced by Kevin Stone of the Stone Clinic (not endorsing). That or Stem Cell injections have been shown to increase cartilage density (few papers). Or maybe something like regular PRP injections.

    OR - Osteochondral allograft. So none of the options mentioned.

  7. My understanding is that ACI is for large defects, for which microfracture is not appropriate. Also, the success rate for ACI is higher. It is a long recovery, but can be the only option for patients with large defects of cartilage damage. For younger patients (up to age 55) it is much preferable to knee replacement.

    1. That may be so, that ACI is preferable for larger defects. Still, for the study cited above in #6, the average defect was 2.4 square centimeters -- not large, but not exactly small either. And, again, the conclusion was: "The results show no superiority of ACI over microfracture at 2 years."

      Also the researchers made no comment that ACI performed better for patients with larger lesions -- presumably, if they had spotted such a trend, they would have found some way to mention it, even if it didn't rise to statistical significance (say owing to their relatively small sample size).

      What we do know about the ACI procedure: (1) It's very expensive (2) It's very extensive (peeling the knee wide open) (3) There was a high rate of follow-up surgery (49%) for patients in the original STAR study of Carticel (4) It comes with a number of exclusions (at least according to the original Carticel guidelines): Patients should be younger (under 65 at least), should not have osteoarthritis, should have a defect at the end of the femur (not the tibia or kneecap -- though perhaps this guidance has changed).

      Perhaps there are patients for whom this is the best procedure. But for anyone considering it, it might be wise to do some research first.

    2. Hi. I wanted to follow up because I have had 2 ACI surgeries since I last wrote to you-6 months apart. My second knee was 2 months ago, Dec 26, 2013. I had been in a panic about my knees when I first found your blog (and ordered your book) because at age 49, I was becoming disabled and doctors (4 orthopedic surgeons) said there was nothing to be done! Because of your book, I got an MRI, which I had to push my insurance to get, and that was the turning point-when the extensive cartilage damage was revealed and the cause being the structure of my knee cap which had caused the cartilage to wear away to the bone. So it was not softening of the cartilage as all the docs had said. I will never understand why one of the docto's did not offer me the MRI....I am very grateful for your advice!!! I have had very good progress so far and Iseem to be pain free. I cannot run or do impact activities u til a year out from last surgery though. On the point of micro fracture vs ACI-my impression is that is once you have micro fracture, ACI is not possible. I chose ACI over a knee replacement and so far I am happy with this decision despite a long rehab. If any of your readers want to read about my experience and those of other ACI patients, I posted on under the name Ozzie in hopes of beig helpful to others who are considering this surgery. Thank you again for the info you provide here

    3. PS In addition to ACI surgery on each knee, I also had an osteotomy (Fulkerson) to create space between the parts of my knee that were too close and had caused the damage to my knee. That procedure alone has been huge in alleviating the pain I had experienced for 10 years since there is no more rubbing of bone on bone!

    4. Great to hear! I'm glad this worked out so well (and hope it continues to). Good luck.

    5. ACI is the better procedure. There quite of few more studies showing it now. And they also show that if you have microfracture first, and then ACI (as opposed to going to straight to ACI), the secondary ACI will be much less likely to succeed.

    6. Curious about the reference for that second statement. My doc's said that microfracture leaves all the other options on the table - which is preferable.

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  10. I had microfracture procedure done July 3 2012, I will be heading in for ACI on December 3. Micro fracture did not create enough tissue to fully fill in for my defect. I'll try to remember to post again after my ACI, hopefully better results!

  11. hey could any one please tell me the average cost of micro fracture and ACI please

  12. terrel brandon and chris webber said microfracture ended their career & greg oden is still not back from his sugery.

    1. Well, I think that, more accurately, their bad knees ended their careers (and microfracture surgery failed to restore their knees). Yes, microfracture often fails, especially with NBA players (who subject their knees to incredibly intense pounding). What amazes me is that it has worked at all for any NBA players. But hopefully better procedures (the thing Kobe had?) will emerge.

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