I have seen such an operation with my own eyes in the operating room. This is true in the movie. Take off a skull just like in the movie, drill four holes with a craniotomy drill (without a saw, the human skull is very hard, and the electric drill is special, which is different from drilling the wall, and it is very expensive, and it costs hundreds of thousands of imported ones), and then use a milling cutter (unlike in the movie, but it can be guaranteed that it will not be sawed).

The removed bones can't grow, unlike muscles or skin, so the removed skulls should be put in a 4-degree incubator and put back after surgery if necessary.

PS: gamma knife and the like don't need craniotomy. In fact, gamma knife is not a scalpel, but radiation to burn intracranial tumors, which does not belong to the scope of surgery.