Article: Pedicle guide for thoracic pedicle screw placement Journal: International Journal of Biomedical Engineering and Technology (IJBET) 2012 Vol.10 No.3 pp.211 - 220 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. Inderscience Publishers - linking academia, business and industry through research

Title: Pedicle guide for thoracic pedicle screw placement

Authors: Kingsley Abode-Iyamah; Luke Stemper; Shane Rachman; Kelly Schneider; Kathryn Sick; Patrick Hitchon

Addresses: Department of Neurosurgery, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City IA 52242, United States ' Department of Neurosurgery, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City IA 52242, United States ' Department of Neurosurgery, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City IA 52242, United States ' Department of Neurosurgery, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City IA 52242, United States ' Department of Neurosurgery, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City IA 52242, United States ' Department of Neurosurgery, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City IA 52242, United States

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.

Keywords: pedicle guide; thoracic pedicle screws; PSG; pedicle screw guide; thoracic anatomy; pedicle screw placement; biomedical engineering; thoracic spine; radiation risk; surgery; accuracy; cost; intra-operative imaging.

DOI: 10.1504/IJBET.2012.050290

International Journal of Biomedical Engineering and Technology, 2012 Vol.10 No.3, pp.211 - 220

Published online: 12 Dec 2014 *

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Title: Pedicle guide for thoracic pedicle screw placement

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