Contaminated open fracture and crush injury: a murine model

Abstract

Modern warfare has caused a large number of severe extremity injuries, many of which become infected. In more recent conflicts, a pattern of co-infection with Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus has emerged. We attempted to recreate this pattern in an animal model to evaluate the role of vascularity in contaminated open fractures. Historically, it has been observed that infected bones frequently appear hypovascular, but vascularity in association with bone infection has not been examined in animal models. Adult rats underwent femur fracture and muscle crush injury followed by stabilization and bacterial contamination with A. baumannii complex and methicillin-resistant Staphylococcus aureus. Vascularity and perfusion were assessed by microCT angiography and SPECT scanning, respectively, at 1, 2 and 4 weeks after injury. Quantitative bacterial cultures were also obtained. Multi-bacterial infections were successfully created, with methicillin-resistant S. aureus predominating. There was overall increase in blood flow to injured limbs that was markedly greater in bacteria-inoculated limbs. Vessel volume was greater in the infected group. Quadriceps atrophy was seen in both groups, but was greater in the infected group. In this animal model, infected open fractures had greater perfusion and vascularity than non-infected limbs.

Open fractures: Investigating infection and recovery

A rodent model for studying extreme injuries such as open fractures and crushing of bones gives insight into wound infection and recovery. Severe bone injuries sustained in warfare are susceptible to infection from bacterial pathogens such as Acinetobacter baumannii (ABC) and methicillin-resistant Staphylococcus aureus (MRSA). Little is known about the process of recovery from such injuries. Shawn Gilbert and co-workers at the University of Alabama at Birmingham, USA, created a rodent model to investigate the role of blood vessel structures in the bone during contaminated injuries. The researchers compared two groups of injured rats, uninfected and infected with ABC and MRSA, and monitored blood vessel behavior and blood flow in the injured limbs. Results indicate that infected open fractures experienced greater blood flow and quicker recovery of blood vessel structures than non-infected injuries.

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