Why does a person with compound fracture needs an emergency operation? what will happen to him if there's a delay in the operation?

Infection: The longer the broken bone stays "open" & exposed to the environment, the greater the risks of infection. Infection can be difficult to cure & leads to fracture healing complications.

Open or compound : Fractures are associated with a higher incidence of infection , the higher the energy and the larger the hole in the tissue that leads to the bone the greater risk for infection with a fracture. Studies have shown that early cleaning and washing of these fractures and care of the fracture if possible or if needed with fixation leads to a better outcome. Particularly with respect to infection there is a critical time frame where washing the fracture out lowers the the infection rate there are other factors such as the use of proper antibiotics the proper debridement of wounds and as noted before whether not to fix the fracture fully or partially to the fracture or not however the main thing about compound open fractures this that they need medical treatment right away so the right decision can be made made.