There were four main approaches to performing early craniotomies
- Drilling – As in trepanning with a circular saw
- Sawing- Using intersected straight lines
- Scraping – Repetitive movement wears down the bone
- Grooving – A Gauging tool cuts a circular channel in the cranium
Scraping and grooving were earlier techniques used in Europe by Neolithic man, by the Incas in Peru and Mexico and tribes in Africa. Drilling (trepanning) and sawing were more common in Europe.
Another method used later in the 19th century was to trepan two small holes through which would be passed a Gigli saw (a fine barbed wire with handles at either end) which would then be used to saw through the bridge. Using three or more points in this way a plate could be removed.
It was a safe method because the saw was pulled away from the brain and as the edges of the bone plates could be angled it was also possible to replace the bone securely before closure.