Connecting the femur to the tibia, the anterior cruciate ligament (ACL) rupture is one of the most devastating injuries in sports.
    
Not only is the ACL inelastic and prone to popping, it is incapable of healing itself, causing surgeons to rely on autografts for reconstruction.
    
Most common is the bone-patellar tendon-bone (BPTB) graft, in which the surgeon removes part of the patellar tendon to replace the damaged ACL.
    
"BPTB autografts have a high incidence of knee pain and discomfort that does not go away," said Guillermo Ameer, professor of biomedical engineering at Northwestern University.
    
"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," said Ameer.
    
Ameer and his research team are working to engineer such a product by combining three components: polyester fibres that are braided to increase strength and toughness, an inherently antioxidant and porous biomaterial previously created in Ameer's lab, and calcium nanocrystals, a mineral naturally found in human teeth and bones.
    
During ACL reconstruction surgeries, tunnels are drilled into the femur and tibia bones to hold the new ligament in a fixed position.
    
Ameer created a bone-like material by combining his antioxidant biomaterials with the calcium nanocrystals; he then embedded braided polyester fibres into it. The artificial ligament's bone-like ends healed to the native bone in the drilled tunnels, anchoring the ligament into place.
    
By studying an animal model, Ameer and his team noticed that the animal's natural bone and tissue cells migrated into the pores of the artificial ligament, populating it throughout and integrating with the bone tunnels.
    
While long-term studies are necessary to evaluate the potential use of the approach in humans, Ameer is optimistic about the results.
    
"The engineered ligament is biocompatible and can stabilise the knee, allowing the animal to function. Most importantly, we may have found a way to integrate an artificial ligament with native bone," Ameer said.
    
The research was published in the Journal of Tissue Engineering and Regenerative Medicine.

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