title: A porcine model for progressive thoracic scoliosis.
abstract: METHODS
  An IACUC-approved study to create a scoliotic deformity representative of adolescent idiopathic scoliosis.
  
  
  OBJECTIVE
  The goal of this study was to develop a reliable porcine scoliosis model and to evaluate the three-dimensional progression of the deformity.
  
  
  BACKGROUND
  Optimal development of nonfusion techniques for treatment of adolescent idiopathic scoliosis requires a reliable large animal model that achieves a progressive three-dimensional (frontal, sagittal, axial) deformity. Limitations in previous work have led our team to the development of a porcine model.
  
  
  METHODS
  This IACUC-approved study included 18 Yorkshire pigs, obtained at 11 weeks old. Scoliosis was induced through unilateral posterior ligament tethering of the spine via pedicle screw fixation, and ipsilateral ribcage tethering. Progressive deformity was documented with biweekly radiographs. Frontal, sagittal, and axial modifications were assessed using the Cobb method. Animals were observed until severe deformity (>50 degrees) developed, then killed.
  
  
  RESULTS
  Animals were observed for a mean 11 weeks. The mean coronal Cobb angle was 25 degrees immediately postoperatively and 55 degrees at 11 weeks. The mean lordosis increased from 4 degrees postoperative to 24 degrees at final follow-up. Apical axial rotation (posterior elements into concavity) increased from 4% postoperative to 27% at 11 weeks. Rate of coronal curve progression was significantly correlated with the initial Cobb index.
  
  
  CONCLUSIONS
  This study establishes a porcine scoliosis model. With placement of a unilateral ligamentous spinal tether combined with concave ribcage ligament tethering a three-dimensional (frontal, sagittal, and axial) spinal deformity can be obtained. The speed of the progressive deformity leaves significant remaining skeletal growth to assess growth modulating therapies for correction. This work forms the basis for a number of investigative efforts at developing new fusionless therapies for patients suffering from adolescent scoliosis.
authors.affiliation: New York University Hospital for Joint Diseases, New York, NY, USA. fschwab@att.net
authors.forename: Frank
authors.initials: F
authors.lastname: Schwab
authors.forename: Ashish
authors.initials: A
authors.lastname: Patel
authors.forename: Virginie
authors.initials: V
authors.lastname: Lafage
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Farcy
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D018450:Disease Progression; D008141:Lordosis / Q000473:pathology / Q000503:physiopathology; D010865:Pilot Projects; D012399:Rotation; D012600:Scoliosis / Q000473:pathology* / Q000503:physiopathology; D013552:Swine; D013904:Thoracic Vertebrae / Q000473:pathology* / Q000503:physiopathology