Pullout strength of pedicle screws using cadaveric vertebrae with or without artificial demineralization |
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| Institution: | 1. Department of Orthopaedic Surgery, Gyeongsang National University School of Medicine and Gyeongsang National University Changwon Hospital, Changwon, Republic of Korea;2. Department of Orthopaedic Surgery, School of Medicine, Kyungpook National University, 130 Dongduk-ro, Jung-gu, Daegu, Republic of Korea;3. Department of Orthopaedic Surgery, Kyungpook National University Hospital, 130 Dongduk-ro, Jung-gu, Daegu, Republic of Korea;4. Department of Anatomy, School of Medicine, Kyungpook National University, 130 Dongduk-ro, Jung-gu, Daegu, Republic of Korea;5. Biomedical Research Institute, Kyungpook National University Hospital, 130 Dongduk-ro, Jung-gu, Daegu, Republic of Korea;1. Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA;2. Department of Neurosurgery, Zucker School of Medicine at Hofstra, Long Island Jewish Medical Center and North Shore University Hospital, Northwell Health, Manhasset, NY 11030, USA;1. Department of Orthopaedic Surgery, NYU Langone Orthopaedic Hospital, 301 East 17th St, New York, NY, USA;2. Department of Spine Surgery, Denver International Spine Clinic, Presbyterian St. Luke''s/Rocky Mountain Hospital for Children, Denver, CO, USA;3. Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, NY, USA;4. Department of Neurological Surgery, University of California, San Francisco, San Francisco, CA, USA;5. Department of Orthopaedics, University of Kansas Medical Center, Kansas City, KS, USA;6. Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA;7. Department of Orthopaedic Surgery, Washington University, St Louis, MO, USA;8. Department of Orthopaedic Surgery, Baylor Scoliosis Center, Plano, TX, USA;9. Department of Neurologic Surgery, Johns Hopkins Medical Center, Baltimore, MD, USA;10. Department of Neurosurgery, University of Virginia, Charlottesville, VA, USA;11. Department of Orthopaedic Surgery, University of California Davis, Davis, CA, USA;1. Departments of Orthopaedics and Population Health Sciences, University of Utah, Salt Lake City, UT, USA;2. Department of Orthopedic Surgery, Massachusetts General Hospital, Harvard Medical School, 55 Fruit St, Boston, MA, USA;3. The Spine Journal, North American Spine Society, 7075 Veterans Boulevard, Burr Ridge, IL, USA;1. Department of Neurosurgery, Loyola University Medical Center, 2160 S 1st Ave Maywood, IL, USA;2. Stritch School of Medicine, Loyola University Chicago, 2160 S 1st Ave Maywood, IL, USA;3. Department of Radiology, Loyola University Medical Center, 2160 S 1st Ave Maywood, IL, USA;4. Department of Public Health Sciences, Parkinson School of Health Sciences and Public Health, Loyola University Chicago, 2160 S 1st Ave Maywood, IL, USA;5. Department of Neurological Surgery Northwestern University Feinberg School of Medicine 676 N. St. Clair St., Suite 2210 Chicago IL 60611 |
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| Abstract: | OBJECTIVESTo evaluate the differences in the pullout strength and displacement of pedicle screws in cadaveric thoracolumbar vertebrae with or without artificial demineralization.METHODSFive human lumbar and five thoracic vertebrae from one cadaver were divided into two hemivertebrae. The left-side specimens were included in the simulated osteopenic model group and the right-side bones in a control group. In the model group, we immersed each specimen in HCl (1 N) solution for 40 minutes. We measured bone mineral density (BMD) using dual-energy X-ray absorptiometry and quantitative computerized tomography. We inserted polyaxial pedicle screws into the 20 pedicles of the cadaveric lumbar and thoracic spine after measuring the BMD of the 2 hemivertebrae of each specimen. We measured the pullout strength and displacement of the screws before failure in each specimen using an Instron system.RESULTSThe average pullout strength of the simulated osteopenic model group was 76% that of the control group. In the control and model groups, the pullout strength was 1678.87±358.96 N and 1283.83±341.97 N, respectively, and the displacement was 2.07±0.34 mm and 2.65±0.50 mm, respectively (p<.05). We detected positive correlations between pullout strength and BMD in the control group and observed a negative correlation between displacement and BMD in the model group.CONCLUSIONSBy providing an anatomically symmetric counterpart, the human cadaveric model with or without demineralization can be used as a test bed for pullout tests of the spine. In the simulated osteopenic model group, pullout strength was significantly decreased compared with the untreated control group.CLINICAL SIGNIFICANCEDecreased bone mineral density may significantly reduce the pullout strength of a pedicle screw, even though the range is osteopenic rather than osoteoporotic. |
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