title: The effect of pedicle screw placement with or without application of compression across the neurocentral cartilage on the morphology of the spinal canal and pedicle in immature pigs.
abstract: METHODS
  Experimental study.
  
  
  OBJECTIVE
  To investigate the effects of pedicle screw insertion on spinal canal and pedicle morphology in immature pigs, and, if transpedicular fixation has an effect, to document whether this occurs because of the inhabitance of the screw inside the growth plate (neurocentral cartilage [NCC]) or because of compression applied across the NCC.
  
  
  BACKGROUND
  Transpedicular fixation has been less commonly applied to the pediatric population, especially because of the risk of damage to the NCC.
  
  
  METHODS
  Twelve newborn pigs (4-6 weeks of age) were operated on. Left sided pedicles from L1-L5 were studied, while right sides served as controls. Pigs were randomly assigned into 3 groups: (1) pedicles were probed only; (2) screws were inserted; and (3) after screw insertion, a washer and a nut were engaged at the pedicle entry point so that gradual compression across the NCC was achieved. After 4 months, spiral computerized tomography was used to measure the pedicle lengths and size of the halves of the spinal canal.
  
  
  RESULTS
  In group 1, the operated hemi-canal area was not statistically different from the nonoperated side (P = 0.159). Pedicle screw insertion either with (P = 0.007) or without (P = 0.005) compression resulted in smaller hemi-canal area and shorter pedicles at the operated side, respectively (P = 0.008, P = 0.021). Approximately 4% to 9% shortening of the pedicle lengths and 20% to 26% narrowing of the hemi-canal areas on the instrumented side occurred with transpedicular instrumentation (groups 2, 3).
  
  
  CONCLUSIONS
  Even without compression, pedicle screws passing through the NCC in immature pigs disturb spinal canal growth significantly. Clinical relevance for young children should be studied further.
authors.affiliation: Department of Orthopedics, Hacettepe University, Faculty of Medicine, Ankara, Turkey.
authors.forename: Akin
authors.initials: A
authors.lastname: Cil
authors.forename: Muharrem
authors.initials: M
authors.lastname: Yazici
authors.forename: Kenan
authors.initials: K
authors.lastname: Daglioglu
authors.forename: Ustun
authors.initials: U
authors.lastname: Aydingoz
authors.forename: Ahmet
authors.initials: A
authors.lastname: Alanay
authors.forename: R Emre
authors.initials: RE
authors.lastname: Acaroglu
authors.forename: Mahir
authors.initials: M
authors.lastname: Gulsen
authors.forename: Adil
authors.initials: A
authors.lastname: Surat
mesh_terms: D000818:Animals; D001863:Bone Screws / Q000009:adverse effects*; D002358:Cartilage, Articular / Q000293:injuries / Q000473:pathology / Q000601:surgery; D005260:Female; D016268:Internal Fixators / Q000009:adverse effects*; D008159:Lumbar Vertebrae / Q000469:parasitology / Q000601:surgery; D008297:Male; D023421:Models, Animal; D013115:Spinal Canal / Q000293:injuries / Q000473:pathology*; D013117:Spinal Cord Compression / Q000209:etiology / Q000473:pathology*; D013123:Spinal Fusion / Q000009:adverse effects* / Q000295:instrumentation; D013552:Swine