Control of Pedicle Screw Placement with an Electrical Conductivity Measurement Device: Initial Evaluation in the Thoracic and Lumbar Spine

Figure 3

(a) Characteristics of the course of probe tip impedance values versus depth of pedicle penetration in an intact pedicle and one with pedicle wall perforation. The impedance values in the intact pedicle remain still above the soft tissue impedance while in perforated pedicle values drop down under the baseline of soft tissue impedance. Modified figure from published version in [22]. (b) Illustration of the electromagnetic field in two media with different electrical conductivity. In bone structure with low electrical conductivity the electromagnetic field is concentrated around the probe tip, whereas in soft tissue with higher electrical conductivity the electromagnetic field around the probe tip is spread out. Modified figure published in PediGuard booklet (SpineVision, Paris, France).

(a)

(b)