Digital simulation of unipedicular thoracolumbar vertebroplasty puncture

OBJECTIVE: To measure such operative parameters of unipedicular kyphoplasty as optimal entry point, angle and depth so as to provide rationales for its clinical management and formulate a standardized protocol for unipedicular vertebroplasty. METHODS: Ten dry thoracolumbar specimens were prepared for measurement. The entry and target points were defined according to the Roy-Camille method. A 3mm Kirschner wire was used to puncture and view in the anteroposterior and lateral aspects of radiography until a satisfying position. The outside oblique and upward oblique angles were measured on the radiographic pictures. After extraction, the depth of Kirschner wire was measured. The positions of entry point were changed and the largest upward oblique angle and largest declination angle measured on the radiographic pictures. RESULTS: For safe puncturing, as the outside oblique and upward oblique angles enlarged from T(11) to L(3), the length enlarged from T(11) to T(12) and L(1) to L(3). The accepted error was that the largest upward oblique angle and largest declination angle enlarged from T(11) to L(3). The alteration range for outside oblique angle was extremely narrow. CONCLUSION: The experimental results provide the guiding data for the operative management of unipedicular thoracolumbar vertebroplasty. If the pedicle is too small or the angle too narrow, the operative sophistication of vertebroplasty will be highly demanding.