In the case of an open fracture it may be from contamination outside the body that gets implanted or injected into the wound. That’s the most common cause of an open fracture that becomes infected. A non-union or infected non-union is more chronic and that’s almost always as a result of previous intervention, whether it was surgery or an open fracture. It gets colonized at the time of surgery, sometimes by local skin bacteria or by the surgery itself where there’s a contaminant in the operating room and it lodges in the wound and then just smolders along. There are many potential etiologies. A lot has to do with the condition of the soft tissue. An infected fracture can happen just because you have very traumatized soft tissues and the body therefore doesn’t have its normal defenses to fight off a low-grade contamination. It can happen just from a routine injury where its contaminated or it can happen as a result of poor soft tissues that are not able to provide the body normal defenses.