The team examined over 600 sculls from South America from 400 BCE to the mid-1500s CE. The earliest had survival rate of 40%, then it jumped to 53%, during the Inca period it was 75% to 83%, and the latest period survival rates was at 91%.

According to Civil War medical records which was from 1861 to1865 , some 46% to 56% of cranial surgery patients died.

More on this: South America’s Inca civilization was better at skull surgery than Civil War doctors | Archive link

Edit: This post’s title was “South America’s Inca civilization was better at skull surgery than US Civil War doctors, some 400 years later”. After taking into consideration the comment section, I changed it to the current one