Autologous Chondrocyte Implantation or Microfracture?

The current issue of AJSM has two great articles regarding articular cartilage repair  procedures that go very well together.  I think this is an amazing aspect of orthopedics as we are making ground on developing ways to restore normal cartilage.  The Cartilage Defectimplications of this are staggering.  If you share an interest in articular cartilage repair, I recommend you read the special issue of JOSPT on articular cartilage and meniscal repair procedures that I guest edited, specifically my guest editorial and my article on postoperative rehabilitation following articular cartilage repair procedures.

Autologous Chondrocyte Implantation Compared to Microfracture

The first study is a comparison of outcomes between microfracture and second-generation autologous chondrocyte implantation (ACI).  80 patients with grade III-IV cartilage defects of the femoral condyle or trochlea were enrolled in the study and split evenly between groups.  The second-generation ACI procedure used Hyalograft C.

microfracture pickingBoth groups showed significantly greater results at the 5 year post-op mark, however, the ACI group showed greater improvements in the International Knee Documentation Committee objective and subjective scores.  Even more interestingly, the return to sports rate between groups was similar at the 2-year mark and remained stable for the ACI group, but decreased for the microfracture group.

Results of Autologous Chondrocyte Implantation in Patients with Failed Prior Treatment

The second study prospectively assess the results of 126 patients undergoing ACI after a failure of a previous articular cartilage repair procedure.  This is a very large and prestigious study by the STAR group (Study of the Treatment of Articular Repair), which consists of all the best cartilage repair surgeons in the country.  The past procedures included predominantly debridement (48%) and microfracture (27%), as well as subchondral drilling, abrasion arthroscopy, and osteochondral autograft.

Results of the study were good with 76% of subjects showing successful results for a long duration.  All measurements showed a statistically significant and clinically meaningful improvements after ACI.  However, these results are lower than many of the previously reported outcomes following ACI when used as the first surgical procedure.  Here are photos of before (top) and after (bottom) of ACI for a femoral condyle defect (left) and patella defect (right):

ACI implant on condyle and patella

Clinical Implications

Putting the results of these two studies together leads to a very interesting and meaningful result.  While ACI and microfracture may yield similar post-op results at the 2-year follow-up, the ACI procedure continues to show durable results while the microfracture group slowly deteriorates over time.  This is significant when looking at these two studies together.  Although ACI appears to be a valuable surgical procedure for failed articular cartilage repair procedures, results of ACI used as the primary procedure are better than when used secondary after another procedure (such as microfracture) fails.  Based on these results, it may be better to have the ACI in the first place rather than try a microfracture.

These results make sense, as the ACI procedure has been shown to result in Type II collagen tissue similar to native articular cartilage while the microfracture is predominantly Type I collagen.  Think of the ACI procedure as restoring cartilage while the microfracture just creates a “scab” of a fibrin clot that simply covers the defect.  Because this tissue is inferior to Type II collagen, it does not hold up as well to weightbearing and functional loading.  Unfortunately the negative of the ACI procedure is a long rehab course and longer time to return to full activities, but based on these studies the slight delay may be worth it to prevent future complications.

Have you seen these results in your clinic?  Would you agree or disagree?  There are a lot of pros and cons with both procedures.  Hopefully as we continue to improve our knowledge and techniques all repair procedures will show better results.

E. Kon, A. Gobbi, G. Filardo, M. Delcogliano, S. Zaffagnini, M. Marcacci (2008). Arthroscopic Second-Generation Autologous Chondrocyte Implantation Compared With Microfracture for Chondral Lesions of the Knee: Prospective Nonrandomized Study at 5 Years The American Journal of Sports Medicine, 37 (1), 33-41 DOI: 10.1177/0363546508323256

K. Zaslav, B. Cole, R. Brewster, T. DeBerardino, J. Farr, P. Fowler, C. Nissen (2008). A Prospective Study of Autologous Chondrocyte Implantation in Patients With Failed Prior Treatment for Articular Cartilage Defect of the Knee: Results of the Study of the Treatment of Articular Repair (STAR) Clinical Trial The American Journal of Sports Medicine, 37 (1), 42-55 DOI: 10.1177/0363546508322897


14 replies
  1. Ian Manning
    Ian Manning says:

    I was under the impression that insurance would not cover ACI surgery unless a microfx had been attempted first and subsequently failed. That could be different now with the ACI technique gaining more traction and showing better outcomes.

    I agree that the rehab following ACI is a little more difficult but honestly feel that the hardest part is lowering your activity level to allow the surgery to take/heal. It may be interesting to see failure rates against activity level for both surgeries. Even with a microfx procedure if you weight bear too early you can “pick the scab” which could lead to surgical failure.

    The other side of it is looking at your patient population. If someone is young and active they should probably look into ACI to get back to their previous level of activity. If someone is older and not as active microfx might be all that is necessary. ACI may still be a case by case surgery vs. the gold standard for the time being.

  2. O
    O says:

    When I asked for ACI back in 2005, my HMO provider (Kaiser) said it was experimental and hence would not cover it.

    How several years later I go to bed every night with pain.
    It’s unfortunate that good treatments like CI exist but they are often inaccessible.

  3. William
    William says:

    after being injured in Iraq I had a stage 4 chrondral fracture to my patella and they preformed a microfracture in nov 2005. in the past 5-6 months the pain when going down stairs and walking more then a short distance has been irritating my knee. I have been given medicine to try for the next few weeks but was advised i may have to see a orthopedic again. i am not sure what else they can do for it. Anyone have any suggestions on what i can expect?? I don’t think i have much cartilege left in there after seeing my pictures from the video they took.

    Thank you all for your responses.

    DINESH says:

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  5. j000
    j000 says:

    Hi all I'm suffering from chodnral defect and condyle defect and was advised to go for ACI. Unfortunately, the procedure is available where I reside. Can anyone tell me what agencies treat using ACI and where in the world are they located. I'm willing to try the treatment I feel I have nothing to lose. I've been enduring a 9 years pain. Thanks

  6. amy castillo
    amy castillo says:

    I too see mainly microfx too. Can’t remember last time I saw ACI. The last one I do remember had 2 condylar lesions, 8 months rehab(lucky she is a RN and in with the PT’s here).

    At 56 and 6-7? years later she is kneeling, squating and runs short races, race walks 1/2 marathons- I say it worked. Dr B Cole did hers.

  7. Patrick Willson PT, COMT, CSCS
    Patrick Willson PT, COMT, CSCS says:

    Thanks for the info Mike. Is there any progress for treating glenoid lesions with ACI? Where would I be able to access the current rehab guidelines for Genzyme? Thanks in advance. Keep up the excellent work with the site.

  8. Mike Reinold
    Mike Reinold says:

    Yes the rehab was brutal. I re-worked the guidelines for Genzyme a few years ago, they are pretty normal now. I must say that my experience with patellar ACI’s were a little worse than a condyle lession. I think it comes down to lesion specifics. If it is a nice contained, small lesion, then microfx may work. The next generation of ACI is on the way and should be even better – no periosteal graft.

  9. Patrick Willson PT, COMT, CSCS
    Patrick Willson PT, COMT, CSCS says:

    I’ve had the opportunity to work with both but the ACI group was over 10 years ago. At that time the rehab was painfully slow for PT and patient. The group I currently work for utilizes microfracture predominantly and generally in the trade professions. These people are generally overweight and are hard on their knees at work. There is a high percentage of these that come back after 1-2 years with swelling, knee pain, meniscal tears… I’ve never seen an ACI patient return or have complications after discharge. How has everyone’s experience been with ACI with patellar vs chondral lesions?

  10. Mike Reinold
    Mike Reinold says:

    I agree and have seen great short term results, but this study makes sense, the repair tissue just isn’t the best quality.

  11. Trevor Winnegge
    Trevor Winnegge says:

    our docs use only microfractures and get great results. however, i have only worked with them for 1.5 years. would be interesting to get these patients back in 5 years and talk to them. this study doesn’t bode well for greg oden!!!!!

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