title: Does removing the spinal tether in a porcine scoliosis model result in persistent deformity? A pilot study.
abstract: BACKGROUND
  Using a tethering technique, a porcine model of scoliosis has been created. Ideally, tether release before placement and evaluation of corrective therapies would lead to persistent scoliosis.
  
  
  OBJECTIVE
  Does release of the spinal tether result in persistent deformity?
  
  
  METHODS
  Using a unilateral spinal tether and ipsilateral rib cage tethering, scoliosis was initiated on seven pigs. The spinal tether was released after progression to a Cobb angle of 50°. Biweekly radiographs were taken for 18 weeks after tether release to evaluate longitudinal changes in coronal and sagittal Cobb angles. Postmortem fine-cut CT scans were used to evaluate vertebral and disc wedging and axial rotation; results were compared to a previously published data set of 11 animals euthanized before release of the tether (control group).
  
  
  RESULTS
  Radiographic analysis demonstrated two responses to tether release: a persistent deformity group and an autocorrective group. Differences between these two groups included number of days with the tether in place before reaching a Cobb angle of 50° and degree of deformity immediately after scoliosis induction. CT analysis of the tether release versus tether intact groups demonstrated progression in vertebral body wedging without differences in apical rotation.
  
  
  CONCLUSIONS
  With the appropriate inducing parameters, release of the spinal tether does not systematically result in deformity correction. Tether release resulted in a reduction in Cobb angle in the first several weeks followed by steady curve progression. Deformity progression was confirmed using detailed CT morphometric analysis.
authors.affiliation: Department of Orthopedic Surgery, NYU Hospital for Joint Diseases, 380 2nd Avenue, Suite 1001, New York, NY 10010, USA. md.ashish@gmail.com
authors.forename: Ashish
authors.initials: A
authors.lastname: Patel
authors.forename: Frank
authors.initials: F
authors.lastname: Schwab
authors.forename: Renaud
authors.initials: R
authors.lastname: Lafage
authors.forename: Virginie
authors.initials: V
authors.lastname: Lafage
authors.forename: Jean Pierre
authors.initials: JP
authors.lastname: Farcy
mesh_terms: D000818:Animals; D001863:Bone Screws; D004195:Disease Models, Animal; D018450:Disease Progression; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000254:growth & development / Q000601:surgery*; D008297:Male; D019637:Orthopedic Procedures / Q000295:instrumentation*; D010865:Pilot Projects; D016059:Range of Motion, Articular; D012272:Ribs / Q000254:growth & development / Q000601:surgery; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology; D013552:Swine; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000254:growth & development / Q000601:surgery*; D013997:Time Factors; D014057:Tomography, X-Ray Computed