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Study: Biocompatible scaffold delivers agents to grow bone and fight infection
SAN DIEGO, U.S.A. — A biocompatible polyurethane scaffold that delivered high doses of recombinant human bone morphogenetic protein-2 and vancomycin effectively fought infection in contaminated rat segmental femur defects while fostering new bone growth, based on research presented here.
Researchers compared results with this construct to the same construct with a low-dose of recombinant human bone morphogenetic protein-2 (rhBMP-2; Medtronic). They also looked at the scaffold with just a low- and high-dose of rhBMP-2 without the antibiotics and as controls they used the rhBMP-2 in high and low doses on a collagen sponge.
“These dual purpose implants effectively promote bone regeneration and reduce infection in contaminated defects,” Kate V. Brown, BM, BCh, of London, United Kingdom, said in presenting results with the porous polyurethane (PUR) scaffold at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons.
Release profiles studied
Brown told Orthopaedics Today Europe that in a recent set of trials, “We demonstrated both early and sustained release profiles for growth factors and antibiotics were ideal for bone growth and infection control.”
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At the meeting she said they selected vancomycin because it is broad spectrum and has been shown to have less of an effect on osteoblast viability and other bone production processes in vivo than other antibiotics. Furthermore, the release profile of rhBMP-2 with the scaffold met their inclusion criteria, as it starts off with a burst followed by a more sustained delivery profile.
“The hypothesis of our study was that incorporating both BMP and vancomycin into this composite would enhance bone regeneration and reduce the infections simultaneously in highly contaminated segmental defects,” Brown said.
Six constructs
To simulate a contaminated defect, researchers inoculated rat femur defects with Staphylococcus aureus, but waited 6 hours to debride and treat them, creating “a challenging model in which we know that the treatment with local antibiotics on its own often does not work,” Brown said.
Then, when the investigators manufactured the PUR scaffolds, they incorporated either a low or high dose of powder rhBMP-2 with or without vancomycin. This resulted in six study groups consisting of low or high dose rhBMP-2 on a collagen sponge, the current clinical standard of care; low and high dose rhBMP-2 on a PUR scaffold; and low and high dose rhBMP-2 and vancomycin on a PUR scaffold.
The dual delivery did not alter the release kinetics of either the growth factor or antibiotic, with the PUR scaffolds with high-dose rhBMP-2 generating more bone. Adding vancomycin resulted in significantly more bone at both BMP doses, Brown said.
“The properties of the scaffold are suitable for tissue engineering and clinical application,” Brown told Orthopaedics Today Europe. – by Susan M. Rapp
Reference:
- Brown KV, Li B, Guda T, et al. Decreasing complications in open fractures with a dual-delivery bone graft. Paper #379. Presented at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons. Feb. 15-19. San Diego, USA.
- Kate V. Brown, BM, BCh, can be reached at U.S. Army Institute of Surgical Research (USAISR), Fort Sam Houston, 3400 Rawley E. Chambers, San Antonio, TX 78234 USA; email: katevbrown@aol.com.
- Disclosures: The study was funded by the USAISR Orthopaedic Trauma Research Program.
