There are many different ways of sterilising equipment. Some people are experts in just that. You can use heat, steam, radiation and other methods. What works best often depends on the material the equipment is made from. It may not be good to use extreme temperatures to sterilise some plastics as they would melt.
Design decisions are also made based on the need for sterilisation. Sharp edges and hidden corners are very hard to clean. This means that a designer of medical tools will specifically try to eliminate them from the final product.
Lots of products are ‘single use’. This means that they are thrown away immediately after surgery. Often they are then burned. Making a product single use means that they have to be made in a sterile way but they don’t have to be cleaned again after that. Single use simplifies things but is expensive and bad for the environment.