ACL injuries may not be as notorious as concussions, but they’re a wider threat

ACL injuries may not be as notorious as concussions, but they’re a wider threat

ACL injuries in professional football are on the rise. The injury is as least as serious as the “concussion” disaster story we’ve been hearing about—but it hasn’t changed behavior. And the outcomes may be even worse than they are from head injuries.

As of the end of August 2016, there have been 27 ACL injuries in the NFL, in preseason alone. This is higher than any other year. The upward trend continues possibly due to bigger, faster players. The conventional wisdom that strengthening leg muscles will protect the knee clearly doesn’t match the mass and power increases. No one in athletics is stronger than American football players, yet they rupture their ligaments regularly.

Braces to protect the knee have never worked, despite the brace manufacturers’ best efforts to market them as “protective gear.” The braces strap onto the large muscles of the thigh and calf in an attempt to limit ligament rupturing during extremes of motion. The knee joint must bend and rotate to function normally; however, there simply is no external brace that can control the motion of the femur on the tibia without being screwed into the bone itself. Other than using them for resistance to bruises and providing warmth, athletes in most sports — including skiing — have given them up. Even surgeons only use them temporarily in the immediate post-operative period.

An ACL injury is not benign. Fifty percent of people with ACL injuries develop osteoarthritis within ten years, whether or not they have surgery. Thirty percent of people under 20 re-rupture their ACL-reconstructed knee.

Surgeons’ traditional reconstruction techniques involve taking away a part of the patellar tendon at the front of the knee or the hamstring tendons at the back and side of the knee. Harvesting those critical tissues induces a second injury to the patient. This injury is not benign either. It results in permanent weakness and abnormal knee mechanics to the point where the search for alternative tissues to use is heating up.

The use of allograft (donor) tissues is increasing in ACL reconstruction surgery. The tissue, when harvested from young donors (usually people who die from motorcycle accidents or gun shots) is very rarely rejected. However, the industry is not well regulated, and a variety of tissues and tissue sterilization treatments exist — producing a mixed bag of quality. For example, if irradiation is used to sterilize tissue, it is permanently weakened. Certain tissues such as the graft from the patella tendon (called bone-patellar tendon-bone) is much stronger than grafts from hamstrings or Achilles tendons, which are designed to stretch during normal walking. These tissues have poorer outcomes when used to reconstruct an ACL (which is not designed to stretch). In our experience, the use of bone-patellar tendon-bone donor tissue is the best choice for now.

The body of evidence shows that using one part of a patient’s knee to fix another part is a bad idea. This is driving both the increasing use of donor tissue and the search for better alternatives. Bone-patellar tendon-bone taken from animal tissue, called Z-Lig, is now available in Europe and South Africa after a rigorous prospective double-blind trial demonstrated success. The tissue has been treated to remove the key antigens that cause rejection. The US trial for approval should begin someday soon. The addition of growth factors and stem cells to donor tissue is also under investigation in our facility and others.

At the end of the day, losing a key structure that guides the knee causes devastation to normal knee mechanics. Twenty-seven million Americans have knee arthritis after soft-tissue injuries. And while it’s true that concussions may lead to brain degeneration in some athletes, ACL injuries occur 300,000 times a year in the US alone and lead to arthritis that now affects millions of people. Concussions may kill you, but arthritis ruins your life. Both need better care.

Dr. Kevin R. Stone is an orthopedic surgeon at The Stone Clinic and chairman of the Stone Research Foundation in San Francisco.

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