title: Effects of flexion and extension on the diameter of the caudal cervical vertebral canal in dogs.
abstract: OBJECTIVE
  To quantify changes in the diameter of the vertebral canal with flexion and extension in the cervical vertebral column.
  
  
  METHODS
  Cadaveric biomechanical study.
  
  
  METHODS
  Cadaveric canine cervical vertebral column (n = 16 dogs).
  
  
  METHODS
  All vertebral columns were evaluated with MRI. Group 1 consisted of 8 normal vertebral columns. Group 2 included 8 vertebral columns with intervertebral disc degeneration. Flexion, extension, compression, and tension were applied to the caudal cervical region (C4-5, C5-6, C6-7). Sagittal vertebral canal diameters (VCD) were obtained by measuring the distance between the ventral and dorsal aspects of vertebral canal.
  
  
  RESULTS
  No differences were seen between groups, thus the results are for both groups. Comparison of VCD between flexion and extension with no load revealed a difference of 2.2 mm (28.9%; P < .001). Comparison between neutral position and extension revealed a reduction of 1.5 mm (16.5%; P < .001), whereas comparison between neutral and flexion showed an increase of 0.7 mm (7.7%; P = .001) in VCD. Comparison between neutral with no load and neutral with compression showed a difference of 0.5 mm, with reduction of 5.5% in the vertebral canal (P = .006). Comparison of extension with no load versus extension with tension revealed an increase of 0.7 mm (9.2%) in the vertebral canal (P < .001).
  
  
  CONCLUSIONS
  Cervical vertebral canal diameter decreased significantly with extension and increased with flexion. The results support the presence of dynamic impingement possibly playing a role in diseases characterized by vertebral canal stenosis, such as cervical spondylomyelopathy.
authors.affiliation: Department of Veterinary Clinical Sciences, The Ohio State University, Columbus, Ohio; Universidade Estadual do Norte Fluminense, Campos dos Goytacazes, Rio de Janeiro, Brazil.
authors.forename: Renato M
authors.initials: RM
authors.lastname: Ramos
authors.forename: Ronaldo C
authors.initials: RC
authors.lastname: da Costa
authors.forename: Andre L A
authors.initials: AL
authors.lastname: Oliveira
authors.forename: Manoj K
authors.initials: MK
authors.lastname: Kodigudla
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Goel
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002102:Cadaver; D002574:Cervical Vertebrae; D004283:Dog Diseases / Q000473:pathology / Q000503:physiopathology*; D004285:Dogs; D005260:Female; D055959:Intervertebral Disc Degeneration / Q000503:physiopathology / Q000662:veterinary*; D008279:Magnetic Resonance Imaging / Q000662:veterinary; D008297:Male; D016059:Range of Motion, Articular; D013115:Spinal Canal