title: Pedicle Screw Fixation Study in Immature Porcine Spines to Improve Pullout Resistance during Animal Testing.
abstract: 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.
authors.affiliation: Aix-Marseille Université, CNRS, ISM UMR 7287, 13288, Marseille cedex 09, France; EUROS, Z.E. Athélia III, 824 Voie Antiope, 13600, La Ciotat, France; APHM, Hôpital Sainte-Marguerite, Institute for Locomotion, 13009, Marseille, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Le Cann
authors.affiliation: ICE UPSP, VetAgro Sup, Campus vétérinaire de Lyon, University of Lyon, F-69280, Marcy l'Étoile, France.
authors.forename: Thibaut
authors.initials: T
authors.lastname: Cachon
authors.affiliation: ICE UPSP, VetAgro Sup, Campus vétérinaire de Lyon, University of Lyon, F-69280, Marcy l'Étoile, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Viguier
authors.affiliation: Hôpital Universitaire Necker Enfants malades, Assistance Publique Hôpitaux de Paris, Faculté de médecine Paris Descartes, Université Sorbonne Paris Cité, Paris, France.
authors.forename: Lotfi
authors.initials: L
authors.lastname: Miladi
authors.affiliation: Hôpital Universitaire Necker Enfants malades, Assistance Publique Hôpitaux de Paris, Faculté de médecine Paris Descartes, Université Sorbonne Paris Cité, Paris, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Odent
authors.affiliation: Aix-Marseille Université, CNRS, ISM UMR 7287, 13288, Marseille cedex 09, France; APHM, Hôpital Sainte-Marguerite, Institute for Locomotion, 13009, Marseille, France.
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Rossi
authors.affiliation: Aix-Marseille Université, CNRS, ISM UMR 7287, 13288, Marseille cedex 09, France; APHM, Hôpital Sainte-Marguerite, Institute for Locomotion, 13009, Marseille, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Chabrand
mesh_terms: D000818:Animals; D008159:Lumbar Vertebrae / Q000601:surgery; D065289:Pedicle Screws; D013552:Swine