fb-pixelA new procedure could revolutionize ACL repairs - The Boston Globe Skip to main content

A new procedure could revolutionize ACL repairs

Corey Peak (right) was the first patient to undergo a new type of ACL repair developed by Dr. Martha Murray.Pat Greenhouse/Globe Staff

Dr. Martha Murray stared at an MRI of Corey Peak’s left anterior cruciate ligament and choked back tears. With a mix of relief and astonishment, she said, “Oh, my goodness, it looks great.”

Peak was the first person to undergo the Bridge-Enhanced ACL Repair (BEAR) surgery developed by Murray, an orthopedic surgeon, at Boston Children’s Hospital. Three months after the surgery, Peak’s MRI showed that his ACL had started to naturally knit together.

It was the first indication that the pioneering procedure, which uses a sponge bridge to connect the two torn ends of the ligament, could be a viable less-invasive option for ACL repairs.


On Wednesday, 10 months after that first promising MRI, Murray publicly announced the results from the Phase 1 safety study of the BEAR surgery. All 10 BEAR patients, including Peak, have new, healthy ACLs regrowing where there were originally tears. If Murray and her team at Boston Children’s see positive outcomes in Phase 2, then the procedure could be available for widespread use in three to four years and revolutionize how orthopedic surgeons treat ACL injuries.

In the future, Murray hopes the BEAR procedure will require less recovery time than the 6 to 9 months currently needed for ACL reconstructions with tendon grafts. Also, results from animal testing lead her to believe the BEAR will dramatically reduce the risk of arthritis in surgically-repaired knees. Both would be invaluable developments for athletes at all levels.

“The safety study showed us that this is possible,” said Murray. “The ACL can regenerate and come back. We can let our body do what it does so well.

“We can give it a little piece of machinery like the sponge bridge, rather than taking stuff out and putting something else in like a tendon graft and forcing it to do something that’s not quite as natural. I’m hoping that the BEAR will shift how people look at ACL surgery.”


Each year, approximately 400,000 ACL tears occur in the US, making ACL surgery one of the most common orthopedic procedures. Tom Brady, Rob Gronkowski, Rajon Rondo, and Lindsey Vonn are among the high-profile professional athletes who have had the surgery in recent years. But high school, college, and recreational athletes account for the majority of ACL injuries. And female athletes are more susceptible to ACL tears.

The standard ACL repair removes the torn ligament and replaces it with a tendon graft. Surgeons typically take the graft from the patient’s own patellar tendon or hamstring, then insert it through holes drilled into the shin and thigh bones. The graft is secured with screws.

By contrast, the BEAR procedure requires only a sponge bridge infused with special proteins and stitches. The sponge is positioned between the two torn ends of the ACL, then is injected with the patient’s blood to stimulate clotting and promote healing. Over six to eight weeks, the ends of the ACL grow into the sponge, reconnect, and replace the sponge.

“It has the potential to be a game-changer, but it’s still early in the process,” said Dr. Jo Hannafin, a sports medicine surgeon at New York City’s Hospital for Special Surgery. “These patients will have to be followed for a minimum of two years to determine whether the ACL heals and does that healed ACL stay competent or stretch over time and fail.”


Upon viewing an MRI of Peak’s knee one year after surgery, Murray said, “It looks like a normal knee.” Peak recalled the MRI technician saying it “looks like we put in the healthy knee.”

But, like Hannafin, Murray wonders how the surgically repaired knee will look in a year and, more significantly, in 15 years.

In knees with tendon grafts, patients often develop arthritis 15-20 years after surgery. That can be devastating for an athlete who undergoes ACL surgery as a teenager and has an arthritic knee in his or her mid 30s. In trials done on pigs’ knees, the BEAR surgery appeared to reduce the risk of arthritis.

“Down the road, we think the prognosis will be better for these patients with the BEAR,” said Dr. Lyle Micheli, director of the Sports Medicine Division at Boston Children’s Hospital. “What we’re hoping is that these repairs won’t have those arthritic changes.”

Breaking the ice

While time will tell how the BEAR holds up, Peak, 26, has sailed through the same rehabilitation program prescribed for patients with tendon grafts. Barely 13 months removed from his operation, Peak competes in ultimate Frisbee, plays soccer, cycles to work, swims, cross-country skis, and runs about 30 miles a week. And sometimes he momentarily forgets which knee required surgery.

Peak considers himself fortunate to have connected with Murray and participated in the safety study.

After Peak injured his knee while downhill skiing, a friend told him about “cool stuff going on at Children’s with ACL repairs.” One week after his injury, he met with study coordinator Brett Flutie and discussed the procedure. As a doctoral candidate at the Harvard T.H. Chan School of Public Health with an undergraduate degree in biomedical engineering, Peak was intrigued by the experimental procedure. He opted for the BEAR, and his surgery took place 24 days after he tore his ACL.


“I thought the science was very convincing,” said Peak. “Also, I saw it as a chance to be part of a larger story about the development of a better way to repair an ACL. It really brings me joy to know that my participation helped break the ice and encouraged people to enroll so they could quickly progress the study to Phase 2.”

To be eligible for Phase 1, Murray required that patients be 18-35 years old, with a bottom ligament stump 6-8 millimeters to ensure a solid attachment to the sponge. Additionally, they couldn’t have extensive damage to the knee besides an ACL tear or be more than 30 days out from the injury.

It took only eight months to fill all 20 slots in the safety study — 10 who opted for the BEAR procedure and 10 in a control group who underwent tendon-graft reconstructions. The average age of participants was 24, and Micheli described them all as avid recreational athletes.

Both the BEAR group and the control group progressed through the rehabilitation and recovery process at the same pace, though the BEAR patients regained more of their hamstring strength sooner because they did not have their hamstring tendon used for a graft. Doctors hope the BEAR procedure will require less recovery time than the 6-9 months currently needed for reconstructions with tendon grafts.


Another encouraging sign for the experimental surgery is that no one in the BEAR group had any bad infections or worrisome knee stiffness.

On to Phase 2

For Phase 2, Murray plans to enroll 100 patients who meet the same ACL tear requirements as the Phase 1 participants. The age range will be 14 (with closed growth plates) to 35. Two-thirds will undergo the BEAR procedure in a randomized study.

Murray hopes to start enrolling patients in Phase 2 this summer, and they will be followed for two years.

As more people undergo the BEAR procedure and it becomes more widely known, Murray hopes other surgeons and researchers will offer input on how it could be improved. Already, colleagues around the world are excited about the possibilities. Last week, she traveled to Sweden for an ACL Study Group meeting. After Murray gave an update about the BEAR, surgeons from the US, Europe, and Asia approached and asked how they could become involved.

“I think of it as a mom,” said Murray. “I’ve always thought of it that way. If my kid tears her ACL, I want a surgery that’s as easy on her as possible. If we could make the sponge work as well as the graft, it would be so much easier on patients.”

As Murray works to make ACL surgery easier for patients, Peak is looking to challenge his surgically repaired knee even more. Next up: He hopes to run the 2017 Boston Marathon.

Follow Shira Springer on Twitter at @ShiraSpringer