Sideline Consult

Current Thinking in Surgical Approaches to Meniscus Repair

Bert R. Mandelbaum, MD, DHL (Hon)

Disclosures

April 22, 2016

With a Torn Meniscus, the Clock Is Ticking

Not so long ago, surgeons thought that the meniscus was a vestigial structure. If it was damaged, we cut it out. But the more we have learned, the more we understand about the necessity of this structure. We know now that we should repair significant tears in the menisci of young people when we can and replace the menisci when we can't. At the same time, our treatments are steadily improving.

The menisci play a vital role in distributing forces that would otherwise concentrate on the articular cartilage or bone. By some estimates, a meniscectomy can more than double tibial femoral contact stresses and therefore be a major contributor to osteoarthritis.[1,2]

This is a particular concern in children who tear their menisci because they run a high probability of developing osteoarthritis within 10-20 years.[2] Fairbank changes consistent with arthritis—such as squaring of the condyles—often develop well before the arthritis itself and can be seen earlier using MRI.[3]

I still manage small tears with partial meniscectomy, simply removing whatever piece may be catching in the joint, as long as I can leave at least 70% of the meniscus intact. If the meniscectomy would leave less than 70% of the meniscus intact, and the patient does not have severe arthritis, I do whatever I can to repair the meniscus. When I cannot repair enough to leave at least 30% of the meniscus, I prefer to replace it with meniscus allograft transplantation.

I like to deal with the tear as soon as possible because I worry that the longer the patient walks around with the tear, the harder it will be to fix. In the short term, a partial or full meniscectomy may eliminate symptoms. But by the time the patient experiences symptoms from arthritis, it's too late.

I cannot yet prove with evidence-based medicine that repairing or replacing the meniscus will prevent osteoarthritis. The studies done so far are in people whose arthritis had already started.[4] Trials will be difficult to design because meniscus tears come in so many shapes and sizes, and the trials would have to last several years because it takes that long for osteoarthritis to develop. In the meantime, I recommend surgery because I know what is likely to happen without it.

Diagnosis: Listening, Physical Exam, and Imaging

The first step in helping these patients is to identify the type of injury. I begin by listening to the symptoms. Was there a pop? Was there some twisting mechanism? What about pain and swelling? These symptoms usually indicate a meniscus tear, sometimes with a ligament tear as well.

Then I go into the physical examination. I use tests such as the McMurray test, which is to flex, extend, and rotate the knee. Catching (locking of the knee) or pain indicates a positive McMurray, which is consistent with a meniscus tear.

Next I look for confirmation from imaging. An x-ray will show bony abnormalities or fragments, fractures, or dislocations. Sometimes it's just a pertinent negative. In 99% of meniscus tears in younger people, x-rays are perfectly normal.

Many generalists will refer the patient to a subspecialist for the next step: an MRI. Meniscus repair is extremely challenging, so the generalists usually want to put their patient in the hands of an expert.

With an MRI, you can confirm the etiology and sort the meniscus tears into one of three broad categories: isolated acute, associated acute, or degenerative.

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