Before advancements in infection control, only conditions that brought patients near death warranted the risk of surgical intervention. If patients survived the operation, infection was nearly inevitable and death by overwhelming sepsis was knocking at their door. In the late 19th century, with the development of germ theory by Louis Pasteur and its subsequent application to surgical sterility by Joseph Lister, surgeons were able to operate with a substantially reduced risk of infection. Consequently, surgeons became more confident and began to explore more extravagant procedures, including elective operations within the cranial vault. As scientific knowledge expanded in the 20th century, so did the advancement of infection control with the use of prophylactic antibiotic drugs, heat sterilization of instruments, and microbial barriers. Recent reports have placed the rate of complications due to infection between 0.75 and 2.32% for intracranial operations.
You may have wondered while using all these surgical tools, instruments and sterilization trays that how did this all came to be. Where did it start and we got to the modern day tools and techniques. Here is a great article on history of infection control and sterilization process