Osteoarthritis 3 Times More Likely After ACL Surgery

People who have had reconstructive surgery for a knee ligament tear develop osteoarthritis in the injured knee three times more often than in the uninjured knee, according to a new study.

About 200,000 anterior cruciate ligament (ACL) injuries happen each year in the United States, and half of those injuries are surgically repaired, according to the American Academy of Orthopaedic Surgeons. Usually, surgeons replace the torn ligament with a grafted replacement.

Researchers have known that reconstructed knees get osteoarthritis more often than healthy knees, but how much the risk increases was hard to determine.

"The time interval between the ACL injury and osteoarthritis is long, usually more than five years," Dr. Bjorn Barenius from  the Karolinska Institutet in Stockholm, Sweden, said. "Ten to fifteen years after the injury is often quoted as a time when you can expect signs of osteoarthritis", he explained

But osteoarthritis can be influenced by many factors, like sustaining more injuries or gaining weight, which might make arthritis hit earlier, he said. 

For the new study, radiologists examined X-rays of both knees of people who'd had ACL surgery at least 14 years earlier. Based on the expert assessments, 57% of ACL-reconstructed knees had arthritis, compared to 18% of healthy knees, according to the results published in The American Journal of Sports Medicine.

How long people had waited between the knee injury and surgery didn't seem to change their likelihood of having arthritis.

Since there was no comparison group of people who had ACL injuries that were not repaired with surgery, it's impossible to say if the surgery or the injury itself increased arthritis risk, Barenius said.

Surgery may help keep the knee from giving way during sports but not restore all of its normal mechanics, he said.

Isolated ACL injuries are rare. The injury is usually complex and includes meniscal tear, which exposes more cartilage to higher wear and tear.For athletes who have ACL reconstruction, osteoarthritis may start to affect their performance many years down the line, but they will have more immediate issues to deal with first, the author claims.

"For most sports and most athletes the instability of the ACL injury will affect their sport more than the future prospect of osteoarthritis," he said.

As far as what patients can do to try to ward off arthritis, Barenius suggests maintaining a healthy weight. Rehabilitation and exercise can help too, Dhaher said. Without surgery, most badly injured knees do develop arthritis, he said.

SOURCE: http://bit.ly/1gWIWzD
Am J Sports Med 2014.

The "Reverse Startle Reflex": Can it avoid "Whiplash" Symptoms?

A Loud Tone Played Before Impact May Reduce Whiplash

NEW YORK (Reuters Health) - If a vehicle could emit a loud tone just before a crash, the sound might startle the occupants and induce muscle reactions that limit the extent of injury, a new study suggests.

A 105 decibel tone emitted just 205 ms before impact appears to reduce the reflexive responses of muscles in the head and neck that ordinarily activate during whiplash, according to research published online August 7 in The Spine Journal.

The results are too preliminary to suggest that a pre-impact tone emitter should become a standard safety device, but the findings merit research in the real world, according to Gunter Siegmund, Director of Research at MEA Forensic Engineers and Scientists in Richmond, BC, Canada, who led the study.

Siegmund told Reuters Health by email, "We know that startle forms part of the neuromuscular response during the kinds of vehicle impacts that can cause whiplash injury. We also know that a loud pre-impact sound can attenuate the startle portion of the response and reduce neck muscle activation levels and head/neck motion. While it seems reasonable to postulate that reduced forces and motion will reduce the likelihood of tissue injury in some individuals, we don't yet know whether this will decrease the rate of actual whiplash injuries in the field."

To study the effect of the tones, 12 volunteers sat in a test sled made up like the driver's seat of a Honda Accord. They each underwent three simulated rear-end crashes either with a tone or without. In each simulation the sled accelerated suddenly at a maximum speed of 19.5 m/s2.

The volunteers were fitted with electromyographic electrodes, both on the surface and inserted into their muscles. They were also fitted with accelerometers to record the motion of the head and torso.

The tone appears to have significantly reduced the amplitude of the C6 multifidus muscle by 42% and the C4 paraspinal muscles by 30%.

Changes in amplitudes in the C4 multifidus and sternocleidomastoid muscles were not statistically significant.

The accelerometers recorded decreased head retraction after the tone by 3.3mm, which was a 9% difference. Peak head angular acceleration in extension and head extension angle were also improved after the tone, while a difference in peak horizontal head acceleration was not found to be statistically significant.

Further testing may require the installation of devices into vehicles because standard crash-test dummies will not be adequate to evaluate muscle responses, Siegmund said.

"Should manufacturers consider including this as a safety feature? I think so," he said. "The technology to detect imminent collisions already exists in some vehicles, and virtually all modern vehicles have speakers that can play a loud tone. Therefore the incremental cost of including this safety system may be relatively low. Two companies have already approached us to commercialize the technology, but I don't know what if anything they are doing with it."

Loud preimpact tones reduce the cervical multifidus muscle response during rear-end collisions: a potential method for reducing whiplash injuries. Spine J 2014.  SOURCE: http://bit.ly/1oRwSd1