Depth control instrument guide for robotic surgery

A method of determining a position of a surgical instrument relative to an instrument holder for a robotic arm, the method comprising:

• attaching the instrument holder to a robotic arm using a coupler, the robotic arm movable to predetermined locations within a three-dimensional coordinate system;
• inserting an instrument into a passage of the instrument holder, the instrument holder comprising:
• a guide body attached to the coupler, the guide body comprising:
• a first end;
• a second end;
• and
• a first passage extending between the first and second ends along an axis to receive an instrument;
• and
• a mechanical or electro-mechanical measuring device comprising:
• an attachment body for releasably coupling to an exterior of the guide body;
• and
• a probe configured to extend into a trajectory of the first passage to contact the instrument and generate positional data;
• moving the instrument into contact with the probe;
• moving a tip of the instrument out of the instrument holder to cause movement of the probe;
• and
• correlating movements of the probe to distances the tip extends out of the instrument holder.

An instrument holder system comprising:

• a guide body comprising:
• a first end;
• a second end;
• and
• a first passage extending between the first and second ends along an axis to receive an instrument;
• a mechanical or electro-mechanical measuring device comprising:
• an attachment body for coupling to the guide body;
• and
• a probe positioned proximate the second end of the guide body and configured to extend into a trajectory of the first passage to contact the instrument and generate positional data;
• and
• an instrument adapter configured to adjust a size of the first passage, wherein the instrument adapter comprises:
• an adapter tube configured to be inserted into the first passage of the guide body;
• a second passage extending through the adapter tube to receive the instrument wherein the second passage of the instrument adapter has a smaller cross-sectional area than the first passage of the guide body;
• and
• a stop flange to prevent the adapter tube from passing through the first passage of the guide body;
• wherein the stop flange is configured to engage the first end of the guide body to position the adapter tube within the first passage spaced from the second end so as to not interfere with the probe;
• wherein the first passage of the guide body and the second passage of the adapter tube are concentrically aligned.