How to turn object into "mesh" or "grid" form but keep the general shape?

Question

I am a non-designer user of Blender. I am designing surgical cutting guide to cut bone in the exact line that I planned. In order to do that, I need the cutting guide to fit with the bone surface which I can do it easily with Boolean modifier. My question is, how to turn my solid object (the surgical guide) to a grid object with many holes as this picture while keeping the fitting surface. The reason for it is to reduce the cost of metal 3D printing. Thank you The source of the image is from the Internet.