Abstract
BackgroundImplant-related osteomyelitis is a major complication that requires immediate treatment, often involving removal of the implant, prolonging patient recovery and inflating expenses. Current research involving interventions to diminish the prevalence of such measures include investigating prophylactic and therapeutic remedies. A proper and accurate animal model is needed to thoroughly investigate such treatments. The scope of this project was to develop an animal model in which a consistent and measurable infection can be formed on an orthopedic implant when bacteria is introduced via a hematogenous source.MethodsTitanium Kirschner-wires were implanted into the intramedullary canals of both femurs. Staphylococcus aureus, ranging from104 to 109 colony forming units, was injected into a tail vessel. After a designated time (3, 7, 14, or 42 days) the femurs were harvested and bacterial numbers determined for both the femur and the implanted K-wire. In addition, histology and micro-computed tomography were used as subjective tools to further characterize the infection.ResultsConsistent infection, that is infection of ≥75 % of the femurs, wasn’t achieved until 107 CFU S. aureus was injected. At 107 CFU, the femurs contained 4.6x106 CFU/g bone tissue at day 3 and 4.8×108 CFU/g bone tissue by day 14. The wire showed comparable contamination with 4.8×104 CFU/mm2 at day 3 and 3.7×105/mm2 by day 14. After 42 days, the bacteria number decreased but was still occupying at 1.9×105 CFU/g bone tissue. There were morphological changes to the bone as well. At day 42, there were signs of osteonecrosis and active bone formation when compared to control animals that received a K-wire but were inoculated with saline.ConclusionsA model for hematogenous osteomyelitis, a common complication associated with implants, has been introduced. A reproducible, preclinical model is essential to evaluate future methods used to mitigate blood-borne bacteria hardware and bone infections.
Highlights
Implant-related osteomyelitis is a major complication that requires immediate treatment, often involving removal of the implant, prolonging patient recovery and inflating expenses
Hematogenous osteomyelitis is a disease primarily found in children but is associated with implants inserted in environmentally sterile conditions, such as those for total joint arthroplasties and fracture fixation of closed fractures
Bacteria enumeration within the blood at time of euthanasia demonstrated that no bacteria were detected in groups that received 107 colony forming units (CFU) or less
Summary
Implant-related osteomyelitis is a major complication that requires immediate treatment, often involving removal of the implant, prolonging patient recovery and inflating expenses. A proper and accurate animal model is needed to thoroughly investigate such treatments The scope of this project was to develop an animal model in which a consistent and measurable infection can be formed on an orthopedic implant when bacteria is introduced via a hematogenous source. Hematogenous osteomyelitis in children is thought to be caused by the anatomy of the metaphyseal region of the long bone [2]. Animal models for hematogenous osteomyelitis in children involve inoculation of bacteria, from a Shiels et al BMC Musculoskeletal Disorders (2015) 16:255 strain known to cause osteomyeltitis, into the bloodstream, often with the use of a sclerosing agent, such as sodium morrhuate, to entrap the bacteria in the blood vessels of the metaphysis of the bone and promote bacteria propagation [3,4,5,6]
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