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Knee News

CMI Safe for Treatment After Lateral Meniscectomy

Collagen Meniscus Implantation (CMI) is a new treatment for people with damaged, destroyed, or removed knee meniscus. The implant is actually a scaffold made from bovine (cow) Achilles tendons. It has been tried with medial meniscal problems. In this report, surgeons from Italy offer their results in the first published study using collagen meniscus implantation for lateral meniscus injuries.

In each human knee, there are two menisci. One is the lateral meniscus (on the outside of your knee) and the other is the medial meniscus (on the inside of the knee). The menisci are attached to the tibia (lower leg bone) by ligaments. The menisci are important because they act as shock absorbers. They stabilize the knee and allow your body weight to be evenly distributed across the joint. The menisci protect and lubricate the articular cartilage (a separate layer of cartilage right next to the joint).

In the past, damaged menisci causing pain and other joint problems would have just been removed surgically. But when we realized joint degeneration leading to early osteoarthritis develops without the meniscus, surgeons started to repair rather than remove this protective cartilage. Eventually, efforts to replace (not just repair) the cartilage were developed. Collagen meniscus implantation (CMI) is an example of this type of regenerative treatment technique.

The scaffold of bovine tissue developed for this purpose is used to fill partial defects (holes or lesions) in the meniscus. The procedure for lateral meniscus implantation is the same as the one used for medial meniscus implantation. After removing the flapped over or torn piece of meniscus, the remaining meniscus is smoothed and shaped carefully to accept the graft. Tiny holes are drilled around the edges of the defect. This step helps create some bleeding that will aid healing and recovery. Once the implant is placed in the hole, the edges are stitched down to hold it in place.

In this study, 24 patients with irreparable lateral meniscus tears received the CMI treatment. Their ages ranged from 16 years old to 53 years old. Without the CMI treatment, these partial tears would have required removal of the damaged cartilage. The risk of early, degenerative arthritis in this age group is a major reason for the use of this new surgical technique. And the results?

All but one patient experienced significant improvements with decreased pain, better knee joint motion, and improved function. Although the knees were stable, not everyone was able to return to their preinjury level of sports or athletic participation. Clinical measurements and repeat MRIs taken over a two-year period of time showed gradual, progressive improvements right up until the end of the study period.

The MRIs showed a partial (not complete) filling effect with collagen meniscus implantation (CMI) therapy. The reason(s) for this remain unknown. It's possible that chronic injuries that are not treated soon enough just can't recover as well as acute (early) meniscal injuries. There may be just too much damage and degeneration to respond in a robust fashion.

Even so, the authors conclude there's no doubt the use of collagen meniscus implantation is safe and effective for partial lateral meniscal tears. Patients can expect a decrease in their painful symptoms accompanied by an increase in motion and function. Rehab is started right after surgery and continues for a full six-months until full unrestricted activity is resumed.


Stefano Zaffagnini, MD, et al. Arthroscopic Collagen Meniscus Implantation for Partial Lateral Meniscal Defects. A 2-Year Minimum Follow-up Study. In The American Journal of Sports Medicine. October 2012. Vol. 40. No. 10. Pp. 2281-2288.

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*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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