title: The Development of a Representative Porcine Early-Onset Scoliosis Model With a Standalone Posterior Spinal Tether.
abstract: METHODS
  In vivo analysis in a porcine model.
  
  
  OBJECTIVE
  To develop a porcine experimental scoliosis model representative of early-onset scoliosis (EOS) with the use of a radiopaque ultra-high molecular weight polyethylene (UHMWPE) posterior spinal tether.
  
  
  BACKGROUND
  Large animal experimental scoliosis models with substantial growth potential are needed to test new fusionless scoliosis correction techniques. Previously described scoliosis models involve rib procedures, which violate the thoracic cage and affect subsequent corrective procedures. Models omitting these rib procedures have experienced difficulties in producing persistent three-dimensional structural deformities representative of EOS.
  
  
  METHODS
  Scoliosis was induced in 14 immature pigs using an asymmetric posterior radiopaque UHMWPE spinal tether fixated to an offset device at lumbar and thoracic levels. Radiographs were taken at 2-week intervals, and frontal and sagittal Cobb angles were measured. A tether release was performed at the 10-week follow-up, and the animals were observed for another 10 weeks.
  
  
  RESULTS
  Four animals had complications (infections and/or screw breakout) and were excluded from the study. Eight animals developed progressive curves with a mean frontal Cobb angle of 62°. A thoracic lordosis (34°) and a thoracolumbar kyphosis (22°) formed. CT analysis, acquired prior to tether release, showed a mean vertebral rotation of 37° at the apex with a mean vertebral wedge angle of 10°. After tether release, the frontal Cobb angles decreased to 46° at the 20-week follow-up. Sagittal curvature was not substantially affected after tether release.
  
  
  CONCLUSIONS
  We describe a large animal scoliosis model, which exhibits a substantial deformity in three planes without the use of rib procedures additional to a posterior spinal tether. The created deformities showed persistence after tether release. With the management of infection and enhancement of instrumentation stability, the creation of a valid model for testing new devices in fusionless scoliosis surgery seems feasible.
  
  
  METHODS
  Level V.
authors.affiliation: Department of Orthopaedic Surgery, CAPHRI school for Public Health and Primary Care, Maastricht University Medical Centre, Maastricht, the Netherlands; Department of Orthopaedic Surgery, St. Anna Hospital, Geldrop, the Netherlands. Electronic address: robbogie@hotmail.com.
authors.forename: R
authors.initials: R
authors.lastname: Bogie
authors.affiliation: Department of Orthopaedic Surgery, CAPHRI school for Public Health and Primary Care, Maastricht University Medical Centre, Maastricht, the Netherlands.
authors.forename: A K
authors.initials: AK
authors.lastname: Roth
authors.affiliation: Department of Orthopaedic Surgery, CAPHRI school for Public Health and Primary Care, Maastricht University Medical Centre, Maastricht, the Netherlands.
authors.forename: P C
authors.initials: PC
authors.lastname: Willems
authors.affiliation: Department of Orthopaedic Surgery, St. Anna Hospital, Geldrop, the Netherlands.
authors.forename: W
authors.initials: W
authors.lastname: Weegen
authors.affiliation: Department of Orthopaedic Surgery, CAPHRI school for Public Health and Primary Care, Maastricht University Medical Centre, Maastricht, the Netherlands.
authors.forename: J J
authors.initials: JJ
authors.lastname: Arts
authors.affiliation: Department of Orthopaedic Surgery, CAPHRI school for Public Health and Primary Care, Maastricht University Medical Centre, Maastricht, the Netherlands.
authors.forename: L W
authors.initials: LW
authors.lastname: van Rhijn
keywords: Early-onset scoliosis; Radiopaque UHMWPE tether; Rotation; Scoliosis model; Wedging