Pedicle Screw Fixation Study in Immature Porcine Spines to Improve Pullout Resistance during Animal Testing

The porcine model is frequently used during development and validation of new spinal devices, because of its likeness to the human spine. These spinal devices are frequently composed of pedicle screws with a reputation for stable fixation but which can suffer pullouts during preclinical implantation...

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Bibliographic Details
Published in:PloS one 2015-10, Vol.10 (10), p.e0127463-e0127463
Main Authors: Le Cann, Sophie, Cachon, Thibaut, Viguier, Eric, Miladi, Lotfi, Odent, Thierry, Rossi, Jean-Marie, Chabrand, Patrick
Format: Article
Language:English
Subjects:
Age
Animal biology
Animal experimentation
Animal research
Animals
Biomechanics
Bone implants
Cortex
Engineering Sciences
Fixation
Hogs
Implantation
Internal fixation
Laboratory animals
Life Sciences
Lumbar Vertebrae - surgery
Mechanics
Methods
Model testing
Morbidity
Pediatrics
Pedicle Screws
Physiological aspects
Pull-out resistance
Scoliosis
Screws
Spinal surgery
Spine
Spine (lumbar)
Studies
Swine
Thorax
Vertebra
Vertebrae
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Summary:The porcine model is frequently used during development and validation of new spinal devices, because of its likeness to the human spine. These spinal devices are frequently composed of pedicle screws with a reputation for stable fixation but which can suffer pullouts during preclinical implantation on young animals, leading to high morbidity. With a view to identifying the best choices to optimize pedicle screw fixation in the porcine model, this study evaluates ex vivo the impact of weight (age) of the animal, the level of the vertebrae (lumbar or thoracic) and the type of screw anchorage (mono- or bi-cortical) on pedicle screw pullouts. Among the 80 pig vertebrae (90- and 140-day-old) tested in this study, the average screw pullout forces ranged between 419.9N and 1341.2N. In addition, statistical differences were found between test groups, pointing out the influence of the three parameters stated above. We found that the the more caudally the screws are positioned (lumbar level), the greater their pullout resistance is, moreover, screw stability increases with the age, and finally, the screws implanted with a mono-cortical anchorage sustained lower pullout forces than those implanted with a bi-cortical anchorage. We conclude that the best anchorage can be obtained with older animals, using a lumbar fixation and long screws traversing the vertebra and inducing bi-cortical anchorage. In very young animals, pedicle screw fixations need to be bi-cortical and more numerous to prevent pullout.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0127463