Pedicle guide for thoracic pedicle screw placement
by Kingsley Abode-Iyamah; Luke Stemper; Shane Rachman; Kelly Schneider; Kathryn Sick; Patrick Hitchon
International Journal of Biomedical Engineering and Technology (IJBET), Vol. 10, No. 3, 2012

Abstract: Study Design: Experimental design. Objective: The placement of thoracic pedicle screws is challenging requiring intra-operative imaging. While increasing accuracy, these modalities increase intra-operative time, radiation to patient and surgeon and cost. We have designed a Pedicle Screw Guide (PSG) for potential use in the placement of thoracic pedicle screws to provide increased accuracy compared to free hand screw placement. Method: Two spines were imaged to measure the angle between the long axis of the pedicle and the sagittal plane from T1-T12. The cortex at the junction of the transverse process and the superior facet was penetrated using an awl. The PSG was used to make a 20 mm pilot hole into the pedicle along the trajectory calculated from the CT scans. On one side from T1-T12, pedicle screws were placed freehand based on clinical experience. On the other, pedicle screws were placed using the PSG. After placement of the screws, CT scans were obtained and pedicle violation was graded. The degree of violation was recorded for each pedicle (1: no violation, 2: <2 mm violation, 3: >2 mm violation). Results: Two specimens were used with a total of 48 pedicles. Of the total 48-pedicle screw there were a total of 11 pedicle violations. Of these violations, 3(12.5%) were with the use of PSG, all of which were grade 2. There were 8 violations (33%) with the free hand technique. The percent error from the pre-instrumentation CT trajectory angle was 62.3% ± 39.5 and 34.3% ± 23.3 (p = 0.002) for freehand and guide assisted respectively. Conclusion: Free hand placement of thoracic pedicle screws is challenging due to the unique anatomy the thoracic spine. While intra-operative imaging techniques increase accuracy there is radiation risk to the surgeon. The use of the PSG could potentially increase accuracy while reducing cost and the risk of radiation.

Online publication date: Fri, 12-Dec-2014

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