By Jane Ehrhardt
“The biggest innovation we’ve added is a biologic implant,” says Amit Momaya, MD, chief of sports medicine and surgeon in the UAB Department of Orthopaedic Surgery.
Momaya performed Birmingham’s first bridge-enhanced ACL restoration (BEAR), which is the first surgical treatment that allows the body to repair its own ACL. “ACL repair isn’t novel,” Momaya says. “For years, they tried and failed miserably back in the 80s. The re-tear rates then were upwards of 50 percent, leading to the procedure fading out of use.”
But following several decades of research, including funding from the NIL, the procedure now includes a biologic component made up of various proteins derived from bovine collagen. This essentially allows the ACL stump to heal and reconnect with prior tissue on the wall.
The procedure builds a scaffold of stitching between the ends of the torn tissue with the biologic component secured in the middle. That implant is basically a protein-based sponge injected with the patient’s blood to hold and protect blood flowing in the gap of the ACL and allows a natural clot to form. The surgery takes between 30 and 45 minutes. After eight weeks, the implant is absorbed as the body generates the collagen and blood vessels to replace it.
One of the major advantages to maintaining the original ACL tissue, versus the more common reconstruction with tendon grafts, is retaining the nerve fibers. “When you’re jumping and landing, those nerve fibers give you appropriate feedback,” Momaya says. “They essentially give your knee balance and tell it where it is in space.”
That native tissue could also lead to less arthritis down the road. Currently, one in three people will suffer from radiographic knee osteoarthritis within ten years of an ACL injury. Up to 80 percent of patients develop arthritis 15 to 20 years after knee surgery. “Animal studies show that keeping the native tissue may reduce arthritis in knees,” Momaya says. “Time will tell in humans over the next 10 years.”
A third obvious benefit to the procedure is not needing a graft, especially when taken from the patient’s own body. “When you do that, you’re robbing Peter to pay Paul,” says Momaya, who has performed around 2,000 knee reconstructions in his career. Removing that tendon tissue from elsewhere in the body creates weakness in that area that was once whole.
The recovery from the procedure takes around nine months, basically the same as a reconstruction. “This is because it still has to go through the maturation of healing the tissue,” Momaya says. “You can’t speed up that process.”
BEAR patients do take longer initially to show improvement. Whereas reconstruction patients may walk out the door after surgery, BEAR patients are allowed only partial weight bearing of about 50 percent for the first two to four weeks, depending on the meniscus repair. “The flip side is BEAR patients have less pain and get their motion back quicker,” Momaya says.
The decreased pain is because surgeons who use the procedure are able to drill smaller tunnels in the knee. In reconstruction surgery, tunnels run 10mm, but BEAR requires only 3.5mm. “That’s a third of the size, which leads to a dramatic decrease in the pain experience,” Momaya says. The graft is the primary source of additional pain in reconstruction. The third source is the fluid still left in the knee from remnants of the fluid inserted to improve vision during the procedure and the tunnels bleeding for a while.
In studies, the BEAR technique has shown no notable difference from reconstruction surgery in muscle strength, knee joint laxity, or postoperative knee scores. However, it has showed better hamstring strength. BEAR patients also showed faster recovery from symptoms and return to their daily activities.
“My favorite part of this procedure is not having to take a patient’s tissue to revive another part of their body,” Momaya says. “Someday I hope we call that procedure barbaric.”