Sea Corals Used to Develop Better Bone Grafts

Researchers have used sea coral to make improvements to bone grafts that make the structures more compatible with natural bone.

In a clinical trial, researchers partially converted the calcium carbonate natural found in sea corals into coralline hydroxyapatite (CHA). The resulting material, called hydroxyapatite/calcium carbonate (CHACC), was shown to "considerably improve" the outcome of bone grafts in 16 patients.

The results of the small clinical study showed that bone healing was observed in all of the patients after four months and that the CHACC had fully biodegraded after in the patients after two years.

The results are noteworthy because CHA derived from sea corals has been used in bone grafts for many years, but its use has been limited because it had not always fully biodegraded.

"Our methods have considerably improved the outcome of bone grafts by using the partial conversion technique, in which the biodegradable composition from natural coral is reserved. It works in a very similar way to commercially available CHA for conductive bone regeneration, but the better biodegradation properties are compatible with the host tissue's natural bone turnover process," said researcher Zhidao Xia from Swansea University.

"When biomaterials do not biodegrade and remain in skeletal tissue, they may continuously cause problems in the host. In extreme conditions, it is possible that the different mechanical properties of the artificial bone graft may cause a re-fracture or become a source for bacterium growth in infection," Xia said.

Xia and his colleagues say that the CHACC method could become a promising alternative to an autograft, which used pieces of bone from another part of a patient's body to regrow new bone in the injured area. Autografts, besides being painful and uncomfortable, also cause long-term impairment in the area where the bone was taken from.

The CHACC compound Xia and his team developed contains 15 percent CHA in a thin layer around calcium carbonate. In addition to providing a strong, porous structure, the new compound has significantly improved biodegrading properties to support natural bone healing.

In the preliminary clinical study, 11 male and five female patients with a range of four different bone defects were surgically implanted with CHACC. Bone healing was observed after four months after the surgery and the majority of the CHACC biodegraded in the patients within 24 months.

The results of the new compound are promising, but Xia said more work needs to be done to make it better.

"Although our study has provided promising results, the CHACC material does not contain a bone organic matrix, living cells and the ability to induce, rather than conduct, new bone formation. Therefore, our future work is to combine controlled growth factor delivery and stem cell technology in order to develop an even better solution for bone graft materials." Xia said.

A paper detailing the results of the clinical study is published in the journal Biomedical Materials.