Study details

The ACL is a ligament that connects the femur to the tibia inside the knee joint. For decades, it was believed that torn ACLs wouldn't heal because they lack blood flow, and standard treatment has typically included surgery in which the ACL is removed and replaced with a ligament put together with tissues harvested either from elsewhere in the body or from a corpse.

However, in the new study, researchers looked at a previous study of 120 ACL tears, some of which had been surgically repaired and some not, and found that two years post-injury, MRI scans suggested around 30% of ACLs in participants who skipped surgery were healing.

The researchers then developed a specialized, new bracing protocol that keeps an injured knee locked in a 90-degree angle for a month so the ends of the ligament could be held close together to facilitate healing, and recruited 80 participants with torn ACLs.

While braced, the patients also completed physical therapy exercises, like repeated clenching their thigh muscles, to prevent atrophy. The therapists also relaxed the angle of the brace every few weeks and removed it after 12 weeks. Knees were then scanned at the start and end of three months.

The researchers found in reviewing the scans that 90% of the participants saw healing in their torn ACLs. None of the ligaments were fully healed, but according to a four-point scale of ACL health in which a total tear is scored as a zero, 50% of participants were at a grade 1 injury, 40% were at a grade 2, and 10% were at a grade 3, which indicates a nearly intact ACL.

Reaction

Lyle Micheli, a professor of orthopedic surgery at Harvard Medical School and director emeritus of the division of sports medicine at Boston Children's Hospital, said the study is "fascinating."

"It has simply been assumed that in most cases after ACL injury, spontaneous healing in adults was not possible," he said.

Daniel Belavy, a researcher at the Hochschule for Gesundheit in Bochum, Germany, said the study is "groundbreaking," adding that the scans and improvements in the participants' knees show "the ACL can heal after a tear."

Belavy added that if a friend or loved one had just torn an ACL, "I'd say to them, 'Hey, I'd personally wait to see what happens, consider this bracing, but I wouldn't rush to surgery.'"

However, Timothy Hewett, a professor of orthopedic surgery at the Marshall University Joan C. Edwards School of Medicine, said "it does not seem plausible" that ACLs can heal themselves.

Hewett noted the MRIs in the study that appear to show the raw ends of the ACLs rejoining are probably either picking up scarring or being misread. "The term 'healing' should not be used by the authors in this context," he said.

The controversy over the study reminded Micheli of what happened "with tears of the meniscus of the knee."

"Early on, the tendency was to either trim or repair meniscal tears," he said. "Subsequent studies suggested that there is a capacity for healing in many of these cases," and surgery may be unnecessary or counterproductive.

Stephanie Filbay, a senior research fellow at the University of Melbourne and lead author of the study, said she hopes to conduct a large, randomized controlled trial soon which will compare results following the bracing protocol with those who had ACL surgery and those who had no treatment. Filbay is also talking with researchers and therapists around the world about using the bracing protocol and adding data and results. (Reynolds, Washington Post, 6/28)

Learn how clinical advancements and technological innovations are affecting surgery, and how you can prepare for the future of surgery.