title: Biomechanical characteristics of hybrid hook-screw constructs in short-segment thoracic fixation.
abstract: METHODS
  Ex vivo biomechanical testing of human cadaveric thoracic spine segments.
  
  
  OBJECTIVE
  To determine whether a hybrid construct, using a combination of pedicle screws (PSs) and lamina hooks, was equivalent to a PS construct, in a short-segment thoracic spine fixation model.
  
  
  BACKGROUND
  Comparisons have been made among PS, lamina hook, and hybrid screw-hook constructs, but these have generally been in long-segment scoliosis correction. In this study, we compared the hybrid and screw-only constructs in a short-segment thoracic fixation.
  
  
  METHODS
  For pullout testing, matched specimens were used for PS (n = 8) and hybrid (n = 8) constructs. Construct stiffness, and the force required for construct failure, were measured. Dynamic testing was carried out on specimens in the PS (n = 7) and hybrid (n = 7) groups in compression, flexion, extension, and left and right lateral bending. Each group was tested intact, after instrumentation, and after corpectomy.
  
  
  RESULTS
  When compared with the hybrid group, a significantly greater force was required for construct failure in the PS group, and these PS constructs were significantly stiffer. No differences were found between groups in dynamic testing.
  
  
  CONCLUSIONS
  A construct employing PSs is significantly stiffer and more resistant to pullout failure than a hook-screw hybrid construct.
authors.affiliation: Spine Research Laboratory, Center for Spine Health, Cleveland Clinic, Cleveland, OH, USA. jonesg@ccf.org
authors.forename: G Alexander
authors.initials: GA
authors.lastname: Jones
authors.forename: Mark
authors.initials: M
authors.lastname: Kayanja
authors.forename: Ryan
authors.initials: R
authors.lastname: Milks
authors.forename: Isador
authors.initials: I
authors.lastname: Lieberman
mesh_terms: D015519:Bone Density; D001863:Bone Screws; D002102:Cadaver; D004548:Elasticity; D019544:Equipment Failure Analysis; D006801:Humans; D016268:Internal Fixators; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D013123:Spinal Fusion / Q000295:instrumentation*; D013314:Stress, Mechanical; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D016474:Weight-Bearing