Researchers use nanotechnology to engineer ACL replacements

One of the most devastating knee injuries both professional and recreational athletes can endure is a rupture of the anterior cruciate ligament (ACL). Now, a team of medical research engineers is working to craft a tri-component, synthetic graft for ACL reconstruction that may help improve post-surgery results.

The ACL is incapable of healing itself, causing surgeons to rely on autografts for reconstruction. A common method is the bone-patellar tendon-bone (BPTB) graft, which requires the surgeon to remove part of the patellar tendon to replace the damaged ACL, according to a news release on the study. According to the American Association of Orthopedic Surgeons, more than 250,000 ACL surgeries are performed annually in the United States.

“BPTB autografts have a high incidence of knee pain and discomfort that does not go away,” Guillermo Ameer, professor of biomedical engineering at Northwestern University’s McCormick of Engineering and professor of surgery at the Feinberg School of Medicine, said in the news release.

Ameer’s research team is putting forth a product that combines polyester fibers that are braided to increase strength and toughness, an antioxidant and porous biomaterial created by the team, and calcium nanocrystals, a mineral naturally found in human teeth and bones.

“By saving the patient’s patellar tendon and using an off-the-shelf product, one may have a better chance of preserving the natural biomechanics of the knee,” Ameer said.

During reconstruction surgery, tunnels are trilled into the femur and tibia bones to hold the new ligament into a fixed position. Ameer created a bone-like material by combining his antioxidant biomaterials with the calcium nanocrystals, and then embedded the polyester fibers into it, according to the news release.

In Ameer’s model, which was tested using an animal model, the artificial ligament’s bone-like ends healed to the native bone in the drilled tunnels, anchoring the ligament into place.

The researchers noted that the animal’s natural bone and tissue cells also migrated into the pores of the artificial ligament.

“The engineered ligament is biocompatible and can stabilize the knee, allowing the animal to function,” Ameer said.

“Most importantly, we may have found a way to integrate an artificial ligament with native bone,” he said.

The team said longer-term studies are needed to evaluate the potential use of the synthetic graft in humans.