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Collagen-based substitutes have proven themselves in fractures
A randomized, multicenter study comparing Healos to autograft bone in a spinal fusion model is ongoing.
The first prospective trial to compare a bone graft substitute to autogenous bone in treating extremity fractures was for Collagraft, a composite of collagen and a porous calcium phosphate ceramic. The trial was completed in the late 1980s at 19 U.S. trauma centers and included approximately 300 patients.
The study showed that Collagraft was equal to autogenous bone for fracture treatment, and it was approved by the Food and Drug Administration in 1991 as a bone void filler and as a bone graft substitute in acute fractures.
The study found that some advantages of Collagraft, made by Zimmer, included shorter operating times and a lower infection rate at the fracture site than in patients treated with autogenous bone, said Charles N. Cornell, MD, of the Hospital for Special Surgery.
Cornell, the lead clinical investigator, said postmarket surveillance has shown that there do not appear to be any long-term negative effects of using the substitute. “The Collagraft appears to incorporate completely and we have biopsies that show regeneration of normal-appearing bone around the Collagraft implants.”
Some have complained, however, that such collagen-based products have several shortcomings, including an inability to provide initial structural stability, potential immunogenicity and difficulty in controlling their movement.
Perhaps the biggest potential application for bone graft substitutes is in the spine. Cornell said that of the estimated 500,000 bone grafts done annually in the United States, more than half are done in the spine. But there were some early canine studies using Collagraft in spine fusion models that had negative results, a factor that may have limited its use in the spine.
Grip strength Use in spinal fusion
A bone substitute that has had more success in the spine is Healos, a collagen sponge that has each type I collagen fiber coated with hydroxyapatite. It features a porous, open-cell matrix designed to provide scaffolding to support the growth factors and cells that initiate new tissue growth. Healos is made by Orquest, which was recently purchased by DePuy.
In 2000, Healos was launched for use in spine surgery in Europe and there is a randomized, multicenter research study underway in the United States that will enroll 370 patients. The study will evaluate the safety and efficacy of Healos used in conjunction with BAK fusion cages for spinal fusion surgery.
Thomas Bauer, MD, PhD, at the Cleveland Clinic, said Healos has a composition that more closely resembles bone mineral than sintered hydroxyapatite does, and it is also “extremely” osteoconductive. “There are some preclinical spine studies and some abstracts on human clinical studies that have reported good results with Healos.”