A surgical system for penetrating and determining a characteristic of tissue.An instrument generates rotational torque,and a drill bit tool body extends along an axis between a distal end to engagetissue and a proximal end to couple to the instrument. Anemitter operatively coupled to the instrument emits light. A detectoroperatively coupled to the instrument detects light. An emissionlightguide within the tool body transmits light emitted by the emitter towardthe tissue as the instrument rotates the tool body. A detectionlightguide within the tool body is spaced from the emission lightguide andtransmit light reflected by the tissue toward the detector asthe instrument rotates the tool body. The emitter emits light into theemission lightguide along the axis, and the detector detects lightreflected from the tissue exiting the detection lightguide transverse to theaxis when the tool body is coupled to the instrument.
