Fig. 7.

Geometric accuracy of robotic guidance in the phantom study: (a) ${\mathrm{TRE}}_x$ and (b) ${\mathrm{TRE}}_{\varphi }$ for KC and tracker guided approaches, (c) error windows (computed as described in Sec. 2.5) in L4 relative to the planned trajectory of a $6\times 45\mathrm{mm}$ screw (green) based on mean errors for KC (cyan) and tracker (magenta) guidance. The planned screw entry point is marked with a dot.