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Ability of recombinant human bone morphogenetic protein 2 to enhance bone healing in the presence of tobramycin: evaluation in a rat segmental defect model

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Glatt, Vaida, Kwong, Francois N., Park, Kichul, Parry, Nicola, Griffin, Damian R., Vrahas, Mark, Evans, Christopher H. and Harris, Mitchel. (2009) Ability of recombinant human bone morphogenetic protein 2 to enhance bone healing in the presence of tobramycin: evaluation in a rat segmental defect model. Journal of Orthopaedic Trauma, Vol.23 (No.10). pp. 693-701. ISSN 0890-5339

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Official URL: http://dx.doi.org/10.1097/BOT.0b013e3181b01b2f

Abstract

Objective: To determine whether locally applied tobramycin influences the ability of recombinant human bone morphogenetic protein 2 (rhBMP-2) to heal a segmental defect in the rat femur.

Methods: The influence of tobramycin on the osteogenic differentiation of mesenchymal stein cells was first evaluated in vitro. For the subsequent, in vivo experiments, a 5-mm segmental defect was created in the right femur of each of 25 Sprague-Dawley rats and stabilized with an external fixator and four Kirschner wires. Rats were divided in four groups: empty control, tobramycin (11 mg)/absorbable collagen sponge, rhBMP-2 (11 p,g)/absorbable collagen sponge, and rhBMP-2/absorbable collagen sponge with tobramycin. Bone healing was monitored by radiography at 3 and 8 weeks. Animals were euthanized at 8 weeks and the properties of the defect were compared with the intact contralateral femur. Bone formation in the defect region was assessed by dual-energy x-ray absorptiometry, microcomputed tomography, histology, and mechanical testing.

Results: Tobramycin exerted a dose-dependent inhibition of alkaline phosphatase induction and calcium deposition by mesenchymal stein cells cultured under osteogenic conditions. The inhibition was reversed in the presence of 500 ng/mL of rhBMP-2. Segmental defects in the rat femora failed to heal in the absence of rhBMP-2. Tobramycin exerted no inhibitory effects on the ability of rhBMP-2 to heal these defects and increased the bone area of the defects treated with rhBMP-2. Data obtained from all other parameters of healing, including dual-energy x-ray absorptiometry, microcomputed tomography, histology, and mechanical testing, were unaffected by tobramycin.

Conclusions: Although our in vitro results suggested that tobramycin inhibits the osteogenic differentiation of mesenchymal stein cells, this could be overcome by rhBMP-2. Tobramycin did not impair the ability of rhBMP-2 to heal critical-sized femoral defects in rats. Indeed, bone area was increased by nearly 20% in the rhBMP-2 group treated with tobramycin. This study shows that locally applied tobramycin can be used in conjunction with rhBMP-2 to enhance bone formation at fracture sites.

Item Type:

Journal Article

Subjects:

R Medicine > RC Internal medicine
G Geography. Anthropology. Recreation > GV Recreation Leisure

Divisions:

Faculty of Medicine > Warwick Medical School

Journal or Publication Title:

Journal of Orthopaedic Trauma

Publisher:

Lippincott Williams & Wilkins

ISSN:

0890-5339