3-D imaging helps surgeons repair knee injuries in young athletes

Collapsing to the floor, the teenager heard a pop in his knee and knew instantly something was wrong.

Duncan, a 15-year-old high school freshman from Alaska, later learned he had torn his anterior cruciate ligament (ACL), a common knee injury among athletes. Similar to a rubber band, the ACL attaches at two points to keep the knee stable.

“I remember it happening in slow motion and I was thinking, ‘Wow, did this just happen to me?’” he said.

ACL tears have become increasingly common in young athletes over the past decade, said Dr. John Xerogeanes, chief of Emory Healthcare’s Sports Medicine Center.

With the help of biomedical engineers at Georgia Tech, Xerogeanes is pioneering a new ACL surgery for younger patients using three-dimensional MRI technology. MRI scans use a magnetic field and radio waves to create detailed images of the body.

The 3-D models allow surgeons to avoid hitting the growth plate, an area of developing tissue near the ends of long bones in children and adolescents that determines the length and shape of mature bones.

If the growth plate is damaged, “You run the risk of coming up with a crooked leg or short leg and that’s devastating to someone,” said Xerogeanes, who recently performed reconstruction surgery on Duncan’s knee.

Common in college and professional athletes, the rise in ACL tears among children has been fueled by several factors, Xerogeanes said. More kids are playing high intensity sports such as basketball, soccer and football, playing year round and starting younger, he said. New imaging technology also allows doctors to better diagnose the problem.

In 1983, roughly 1 percent of ACL injuries occurred in children ages 14 or younger. Today, they account for more than 3 percent of cases, said Dr. David Geier, director of sports medicine at the Medical University of South Carolina in Charleston. Geier, who performs ACL surgery on children five to 10 times a year, said his youngest patient was 8.

In ACL surgery, surgeons drill tunnels in the upper and lower knee bones, slide in the new ligament, typically taken from a hamstring tendon or donor tissue, and attach it at both ends.

Until now, treatment for children with ACL tears has often involved rehabilitation, wearing a brace and forgoing sports until they’ve stopped growing and surgery can be performed safely, usually by age 14, Xerogeanes said.

Traditionally, surgeons have performed the operation in a non-anatomic way, where the new ligament isn’t placed in the original ACL location, Xerogeanes said. The 3-D technology, however, allows surgeons to see from one point to another on either side of the knee. They can pre-plan the exact location they need to drill to miss the growth plate and still use the original starting and ending points of the ligament.

“The more normal we make your knee movement, the less chance of arthritis and re-injury to the ligament,” said Xerogeanes, who has performed approximately 20 of the surgeries in the past two years.

There is a revolution ongoing in medical imaging, said Allen Tannenbaum, a bioengineering professor at Georgia Tech who helped develop the technology. As imaging machines get more sophisticated, they need computer algorithms to go along with them, he said.

The software created by Tannenbaum and his team for Xerogeanes processes MRI data to create a comprehensive model versus traditional imaging that produces individual, two-dimensional slices of data that don’t reveal all of the information, he said.

“Imagine trying to make a repair on your car, where you just have one slice of it and need to connect a wire,” he said.

Tannenbaum said his team is using 3-D imaging techniques in projects involving tumors, traumatic brain injuries and other areas of study.

Alec and his father learned about the new ACL surgery on the Internet and traveled thousands of miles from their home in Sitka, Alaska, to Emory. Al Duncan said the injury has been tough on his son who also plays baseball and runs cross country. “That’s what he lives for is the competition,” he said.

With his son now recovering, Duncan worries he will try to shoot hoops too early while healing, a process Xerogeanes said takes a full year. Alec, though, said he doesn’t plan on playing pickup games any time soon.

“I don’t want to ruin it any more," he said. "One year is bad enough.”

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