title: Impact of anchor type on porcine lumbar biomechanics: Finite element modelling and in-vitro validation.
abstract: BACKGROUND
  Rigid posterior implants used for spinal stabilization can be anchored to the vertebrae using pedicle screws or screws combined with transverse process hooks. In the present study, a finite element model of a porcine lumbar spine instrumented with screws and hooks is presented and validated.
  
  
  METHODS
  The porcine lumbar spine model was validated using in-vitro measurements on six porcine specimens. Validation metrics included intervertebral rotations (L1 to L6) and nucleus pressure in the topmost cranial instrumented disc. The model was used to compare the biomechanical effect of anchor types.
  
  
  RESULTS
  Good agreement was observed between the model and validation experiments. For upper transverse hooks construct, intervertebral rotations increased at the upper instrumented vertebra and decreased at the adjacent level. Additionally, nucleus pressures and stress on the annulus decreased in the adjacent disc and increased in the upper instrumented disc. The pull-out forces predicted for both anchor configurations were significantly lower than the pull-out strength found in the literature.
  
  
  CONCLUSIONS
  These numerical observations suggest that upper transverse process hooks constructs reduce the mobility gradient and cause less stress in the adjacent disc, which could potentially reduce adjacent segment disease and proximal junction kyphosis incidence without increasing the risk of fixation failure. Future work needs to assess the long-term effect of such constructs on clinical and functional outcomes.
authors.affiliation: Department of Mechanical Engineering, École de technologie supérieure, 1100 Notre Dame Street West, Montreal H3C 1K3, Canada; Research Center, Hôpital du Sacré-Cœur de Montréal, 5400, Gouin Boul. West, Montreal, Quebec H4J 1C5, Canada.
authors.forename: Martin
authors.initials: M
authors.lastname: Brummund
authors.affiliation: Department of Mechanical Engineering, École de technologie supérieure, 1100 Notre Dame Street West, Montreal H3C 1K3, Canada; Research Center, Hôpital du Sacré-Cœur de Montréal, 5400, Gouin Boul. West, Montreal, Quebec H4J 1C5, Canada. Electronic address: vladimir.brailovski@etsmtl.ca.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Brailovski
authors.affiliation: Department of Mechanical Engineering, École de technologie supérieure, 1100 Notre Dame Street West, Montreal H3C 1K3, Canada; Research Center, Hôpital du Sacré-Cœur de Montréal, 5400, Gouin Boul. West, Montreal, Quebec H4J 1C5, Canada.
authors.forename: Yvan
authors.initials: Y
authors.lastname: Petit
authors.affiliation: Department of Mechanical Engineering, École de technologie supérieure, 1100 Notre Dame Street West, Montreal H3C 1K3, Canada; Research Center, Hôpital du Sacré-Cœur de Montréal, 5400, Gouin Boul. West, Montreal, Quebec H4J 1C5, Canada.
authors.forename: Yann
authors.initials: Y
authors.lastname: Facchinello
authors.affiliation: Research Center, Hôpital du Sacré-Cœur de Montréal, 5400, Gouin Boul. West, Montreal, Quebec H4J 1C5, Canada; Department of surgery, Faculty of Medicine, University of Montreal, Pavillon Roger-Gaudry, S-749, C.P. 6128, succ. Centre-ville, Montreal, Quebec H3C 3J7, Canada.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Mac-Thiong
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001863:Bone Screws; D020342:Finite Element Analysis; D006801:Humans; D007738:Kyphosis / Q000503:physiopathology / Q000601:surgery; D008159:Lumbar Vertebrae / Q000502:physiology / Q000601:surgery*; D023421:Models, Animal; D065289:Pedicle Screws; D011312:Pressure; D013123:Spinal Fusion / Q000295:instrumentation*; D053441:Suture Anchors; D013552:Swine
keywords: Finite element modelling; Pedicle screws; Porcine lumbar spine; Proximal junction kyphosis; Spinal fusion; Transverse process hooks