Abstract
Aim
To study the antimicrobial effect of a gentamicin loaded bio-composite bone void filler in relation to a limited or extensive debridement of osteomyelitis lesions, respectively.
Methods
Nine pigs were inoculated into the right proximal tibial bone with a high virulent gentamicin sensitive strain of Staphylococcus aureus (104 CFU). Seven days after inoculation, Group A pigs (n=3) were exposed to a limited debridement of the bone lesion, whereas Group B pigs (n=3) were exposed to an extensive debridement. The bone defects of Groups A and B were filled with (2–5 ml) of an absorbable gentamicin (175 mg/10 mL) loaded bio-composite. The animals of Group A and B were euthanized 12 days after revision surgery. Group C animals did not undergo revision surgery and were euthanized seven (n=1) or nineteen (n=2) days post inoculation in order to follow the development of the untreated infection. None of the animals were treated with systemic antimicrobials. All bones were exposed to a post mortem CT scan and rigours pathological examinations. The surrounding bone tissue and the bio-composite were sampled for microbiology.
Results
All animals developed a substantial purulent bone infection in the inoculated leg prior to revision surgery. In the cases of limited debridement, the bone lesions surrounding the bio-composite bone void filler had clearly expanded since revision surgery, and contained extensive amounts of pus, necrotic bone tissue and oedematous fibrotic tissue. In the cases of extensive debridement, the bio-composite bone void filler was surrounded by only a few mm of fibrosis and sclerotic bone tissue i.e. the bone lesions were not expanding. However, in one pig the bio-composite bone void filler was communicating with a small purulent osteolytic lesion without a sclerotic border indicating appearance after revision surgery. In all pigs, S. aureus bacteria were post mortem cultured from the adjacent bone tissue and the bio-composite surface.
Conclusions
The gentamicin concentrations within the bio-composite could not eradicate the residual infection after debridement. However, extensive debridement and filling of the bone void with gentamicin loaded bio-composite contained the lesion formed by revision surgery, which are important complementing roles as adjuvant to systemic antimicrobial therapy and the immune system in eradication of the infection. The present study emphasizes that extensive debridement is fundamental for successful treatment of bone infections and that antimicrobial loaded bone void fillers or bone substitutes should not be used as an alternative to extensive debridement.
