Tool navigation in mixed reality computer-assisted surgery

A system for tracking a surgical tool relative to a bone in computer-assisted surgery, comprising:

• a processing unit;
• and
• a non-transitory computer-readable memory communicatively coupled to the processing unit and comprising computer-readable program instructions executable by the processing unit for:
• obtaining video images of the surgical tool relative to the bone, from a point of view on an operator;
• processing the video images to merge virtual models of the surgical tool and the bone to the surgical tool and the bone in the video images;
• calculating a location of a working end of the surgical tool relative to the bone using the video images processed, in a concealed condition of the working end of the surgical tool relative to the bone;
• and
• outputting the location of the working end of the surgical tool relative to the bone.