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Microfracture Treatment for Knee Articular Cartilage Injuries Gets the Nod

It's clear now that damage to the meniscus (cartilage) of the knee should be repaired whenever possible. But there's another type of cartilage in the knee called the articular cartilage. This is the cartilage that lines the joint and sits right up against the bone.

We don't know for sure that if left alone, the articular cartilage would eventually heal on its own. The process of what happens over time without intervention or treatment is called the natural history of a condition.

Right now, it's assumed that damage to the articular cartilage leads to arthritis sooner than later. But there's no real evidence to support this view. Most of the studies done so far haven't been on single (isolated) defects of the articular cartilage. Injuries treated have included additional damage to the joint such as an ACL tear (ACL = anterior cruciate ligament).

The articular cartilage doesn't have much of a blood supply of its own. It relies on movement of nutrients in fluids that cross the cartilage bringing supplies like a wagon train. But the fluid can't cross holes in the cartilage and that's a problem. Without a healthy, intact matrix of bone and cartilage, it's like the wagon coming to a canyon with no bridge to get across.

Surgeons have only one study of the natural history of unrepaired articular cartilage to rely on for data. And that was done more than 10 years ago on young athletes. It showed a 79 per cent success rate with no treatment applied.

Since that time, three different surgical techniques have been developed and tried for this type of injury: 1) microfracture, 2) autologous chondrocyte implantation (ACI), and 3) osteochondral autograft transplantation (OAT). Here's a brief explanation of each one.

Microfracture involves drilling tiny holes through the cartilage, past the first layer of bone underneath, and into the bone marrow. There's a rich blood supply there and drops of blood well up through the holes to aid the healing process.

Autologous chondrocyte implantation requires removing some of the healthy cartilage cells, taking them to the lab, growing more healthy cells, and then putting them into the holes or defects in the knee.

And osteochondral autograft transplantation refers to harvesting healthy cartilage cells from a part of the knee that doesn't bear weight (and isn't damaged) and using those plugs to repair the damaged area.

Which one of these three methods is the best and holds up the longest? That's what these orthopedic surgeons wanted to find out. They searched the published studies to find evidence that would support one over another. After comparing all the high-quality studies available, here's what they found.

  • There's a problem in finding studies that consistently look at the same outcomes and use the same research methods. That makes it difficult to compare results from study to study or combine results together for a clearer picture of what's going on over time.

  • Microfracture results in improved knee function in the first two years. It's unclear whether the results last beyond the two-year mark.

  • Osteochondral autograft transplantation (OAT) has some advantages over microfracture when used with young athletes. There were better results and fewer failures with the OAT procedure in this group. More athletes were able to return to their pre-injury level of sports participation after having the OAT procedure compared with microfracture.

  • Results between osteochondral autograph transplantation (OAT) and autologous chondrocyte implantation (ACI) were about the same. There was no clear winner between these two.

  • Microfracture is a one-step operation. The other two procedures (OAT and ACI) are two-step procedures. Microfracture is considered fairly simple and a less expensive way to treat articular cartilage lesions.

    The authors conclude that when looking at pain levels, function, ability to return-to-sport, cost, and overall failure rates over time, microfracture seems to be the best choice for treating articular cartilage defects. Clearly more studies are needed to find out what happens in the long-run and how durable this type of repair really is.

    Studies will continue to be hampered by the fact that it's difficult to include a control group for comparison. With a control group (the patients who don't receive any treatment), it's possible to evaluate the natural history (what happens over time without treatment) and compare it to the results of each of these three other treatment methods.

    The authors also recommend carrying out studies with patients who have isolated cartilage defects (no other knee injuries) and normal knee alignment. This approach would help reduce some of the other factors and variables that can affect results.


    Marc R. Safran, MD, and Kenneth Seiber, MD. The Evidence for Surgical Repair of Articular Cartilate in the Knee. In Journal of the American Academy of Orthopaedic Surgeons. May 2010. Vol. 18. No. 5. Pp. 259-266.

    05/20/2010

    *Disclaimer:* The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic.
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