System and methods for improved access to vertebral bodies for kyphoplasty, vertebroplasty, vertebral body biopsy or screw placement

A method for providing access to the interior of a pedicle for a desired transpedicular procedure, comprising:

• inserting an awl with a separable guide wire in the pedicle at a predetermined starting point and in a predetermined trajectory to a desired depth, removing the awl from the pedicle and leaving the guide wire therein;
• positioning a cannulated drill bit over the guide wire and drilling an elongated opening in the pedicle inwardly to the desired depth;
• removing the drill bit from the opening and the guide wire;
• inserting a first cannula into the opening over the guide wire with the outer end of the first cannula substantially flush with the adjacent portion of the posterior cortex of the pedicle;
• and removing the guide wire from the opening;
• whereby an elongated instrument such as a kyphoplasty balloon catheter, vertebroplasty cannula or vertebral body biopsy needle may be inserted through the first cannula into the interior of the pedicle for the desired procedure.

A method for providing access to the interior of a pedicle for a desired transpedicular procedure, comprising:

• inserting an awl with a separable guide wire in the pedicle at a predetermined starting point and in a predetermined trajectory to a desired depth;
• removing the awl from the pedicle and leaving the guide wire therein;
• positioning a cannulated drill bit over the guide wire and drilling an elongated opening in the pedicle inwardly to the desired depth;
• removing the drill bit from the opening and the guide wire;
• and inserting a cannula into the opening over the guide wire, the cannula comprising an inner section disposed in the opening and an enlarged outer section extending outwardly from the posterior cortex and having a generally longitudinal slot extending therethrough to enable an instrument that is straight or angled to be inserted through the slot and through the cannula into the pedicle after the guide wire is removed.

A method of determining the size and/or placement of screws or other instruments in pedicles during surgery in a selected spinal area, comprising:

• generating a dimensionally true three-dimensional image of the bony spine in the selected spinal area;
• hollowing out the vertebra in the three-dimensional image with cortical wall thicknesses selected by a surgeon performing the surgery such that the individual vertebra can be visualized as a structure that has been hollowed out with the remaining vertebral body being highlighted throughout its walls;
• determining the narrowest diameter or isthmus with each pedicle based on a surgeon's selected pedicle cortical wall thickness;
• generating a straight line starting at the center of the isthmus and extending inwardly to a point centered within the anterior cortex so that it is positioned concentrically within the pedicle without touching the highlighted walls thereof, the line terminating inside the vertebral body a predetermined distance from the anterior inner cortical wall and extending outwardly in the opposite direction to penetrate the posterior pedicle cortex;
• expanding the line concentrically to a diameter that does not exceed the isthmus diameter based on the surgeon's selected pedicle cortical wall thickness, the line being expanded into a cylinder that stops growing when any portion thereof contacts the highlighted inner cortical wall of the vertebral body with the exception of the posterior pedicle cortex;
• determining the length of the cylinder from its innermost end spaced from the anterior inner cortical wall to the point at which the outer end thereof contacts the posterior pedicle cortex;
• and
• calculating the ideal pedicle screw or instrument diameter, length and/or trajectory based on the dimensions and trajectory of the cylinder generated for each pedicle.