Dual pitch screw design provides equivalent fixation to upsized screw diameter in revision pedicle screw instrumentation: a cadaveric biomechanical study
| Autor: | Steven D. Glassman, Ryan Weegens, Joseph L. Laratta, Leah Y. Carreon, Jeffrey L. Gum, Michael J. Voor |
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| Rok vydání: | 2021 |
| Předmět: |
musculoskeletal diseases
Context (language use) Bending Lumbar vertebrae Lumbar Cadaver Pedicle Screws Medicine Humans Orthopedics and Sports Medicine Fixation (histology) Orthodontics Lumbar Vertebrae business.industry Lumbosacral Region equipment and supplies musculoskeletal system Biomechanical Phenomena surgical procedures operative medicine.anatomical_structure Surgery Equipment Failure Neurology (clinical) business Cadaveric spasm Interference fit |
| Zdroj: | The spine journal : official journal of the North American Spine Society. 22(1) |
| ISSN: | 1878-1632 |
| Popis: | Background Context There are situations that require the replacement of pedicle screws. They are often exchanged when loose or broken or to accommodate a different sized rod or pedicle screw system. Traditionally, pedicle screws are replaced by up-sizing the core diameter until an interference fit is obtained. However, this method carries a risk of pedicle screw breach. Purpose To determine if dual pitch screws, with cancellous pitch in the vertebral body and cortical pitch throughout the pedicle, allows for in-line screw revision without upsizing screw diameter. Study Design Cadaveric biomechanical Study Patient Sample Not applicable Outcome Measures Not applicable Methods Pedicle screws were tested in the lumbar vertebrae from eleven cadavers. Standard pitch 5.5 mm screws were inserted and loaded using a "break-in" protocol. Screws were removed and replaced with one of four screw types: 5.5 mm Standard Pitch, 5.5 mm Dual Pitch, 6.0 mm Standard Pitch, or 6.0 mm Dual Pitch. Failure testing was done using a stepwise increasing cyclic loading protocol for 100 cycles at each increasing load level. The loading consisted of a combined axial and bending load simulating the load seen by the most inferior screw. Results Failure was consistent, with the tip of the screw displacing inferiorly into the vertebral body while simultaneously pulling out. Failure strength was lowest in the 5.5mm Standard (135.8±29.4N) followed by 6.0mm Standard (141.8±38.6N), 5.5mm Dual (158.1±53.8N), and 6.0mm Dual (173.6±52.1N, p=.023). There was no difference in the failure strength between the 5.5mm Dual and 6.0mm Standard. Lumbar level (p=.701) and donor spine (p=.062) were not associated with failure strength. Conclusions After pedicle screw removal, screws with a larger core diameter or with a dual pitch have similar failure strengths. Dual pitch screws may allow for in-line revision of screws without upsizing screw diameter, minimizing the risk of pedicle breach or fracture. Clinical Significance Dual pitch screws, with cancellous pitch in the vertebral body and cortical pitch through the pedicle, allows for in-line revision of pedicle screws without upsizing screw diameter; reducing the risk of pedicle breach or fracture when exchanging screws. |
| Databáze: | OpenAIRE |
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