A new technique of bone thickness measurement for pedicle screw insertion safety purpose.

Pedicle Screw (PS) was originally accomplished for Spinal fixation but it has several limitations. If the pedicle screw passes though the cortex bone in surgery, it has a risk to damage the spinal cord and vertebral artery, which can be caused to a serious problem such as paralysis. Therefore, it should be avoided by all possible means. In current situation, it depends on a palpation of doctor to judge the boundary between the cortex and cancellous bone. Although many instrumentation has been described in several clinical studies, there are still lack of data in the literature concerning the measurement of bone thickness in real time mode. Most of the measurements of the bone thicknesses were based on CT Scan machine which is off-line technique. Therefore, the purpose of this prospective study was to develop a real time measurement of bone thickness for safety purpose of pedicle screw insertion. A total of 12 data was collected in each experiment. Ultrasound echo signal for each specimen was measured and used to measured bone thickness. Then, the results were compared with manual measurement of bone thickness which is by using a ruler. The percentage different of bone thickness was small for both methods which were 8.86% for first method and 15.1% for second method. This measurement values showed that the accuracy of bone thickness more than 84% for both method. As a conclusion, both methods were suitable to use as a bone thickness measurement technique for pedicle screw insertion application.