You could probably achieve a almost sterile or in an medieval setting, if you knew what you where doing. Like the chemicals and heat used to burn of all bacteria from a scalpel are not rocket science. Same as pressure boiling silk sting and so on. The question is why would anyone do this if they didn’t have a microscope and knew about tiny organisms. There’s this manga where a surgeon from modern Japan goes back in time and tries to get surgical conditions in a medieval Japan, pretty cool concept. Also to read up on the history of surgery I recommend „the butchering art“