title: Influence of vertebral column distraction on spinal cord volume: an experimental study in a goat model.
abstract: BACKGROUND
  Spinal cord injury may be related to excessive distraction of the spinal cord during surgical correction of spinal deformities by vertebral column resection. This study aimed to investigate how vertebral column distraction influences spinal cord volume to establish the safe range in a goat model.
  
  
  METHODS
  A vertebral column resection was performed on the tenth thoracic vertebra of 11 goats. The spinal cord was distracted until the somatosensory evoked potential signals were decreased to 50 % from baseline amplitude or were delayed by 10 % of the baseline peak latency. The osteotomy segment was stabilized with a PEEK mesh cage filled with bone graft, and the pedicle screws on the rods were then tightened in this position. Spinal cord volume was calculated using Mimics software, and T10 height, disk height, osteotomy segment height, and spinal segment height were measured using the MRI image workstation.
  
  
  RESULTS
  Three goats were excluded, and data obtained from the eight remaining goats were analyzed. The safe limit of distraction distance was 11.8 ± 3.65 mm, and the distraction distance was strongly correlated with the difference between the pre- and postoperative measurements (d value) of spinal cord volume per 1 mm of osteotomy segment height (r = -0.952, p < 0.001), but was not correlated with T10 body height (r = 0.16, p = 0.71), spinal segment height (r = 0.29, p = 0.49), disk height (r = -0.12, p = 0.98), or the d value (pre-post) of spinal cord volume per 1 mm of spinal segment height (r = 0.45, p = 0.26). The mean d value (pre-post) of spinal cord volume per 1 mm of osteotomy segment height was 10.05 ± 0.02 mm(3) (range 10.02-10.08 mm(3)).
  
  
  CONCLUSIONS
  The maximum change in spinal cord volume per 1-mm change in height was in the osteotomy segment, and its safe limit was 10.05 ± 0.02 mm(3). The safe limit of spinal cord distraction can be calculated using the spinal cord volume per unit 1-mm change in height.
authors.affiliation: Department of Orthopedics, Guangzhou General Hospital of Guangzhou Military Command, No.111 Liuhua Avenue, Guangzhou, 510010, People's Republic of China.
authors.forename: Feng
authors.initials: F
authors.lastname: Qiu
authors.forename: Jin-Cheng
authors.initials: JC
authors.lastname: Yang
authors.forename: Xiang-Yang
authors.initials: XY
authors.lastname: Ma
authors.forename: Jun-Jie
authors.initials: JJ
authors.lastname: Xu
authors.forename: Qing-Lei
authors.initials: QL
authors.lastname: Yang
authors.forename: Xin
authors.initials: X
authors.lastname: Zhou
authors.forename: Yao-Sheng
authors.initials: YS
authors.lastname: Xiao
authors.forename: Hai-Sheng
authors.initials: HS
authors.lastname: Hu
authors.forename: Li-Hui
authors.initials: LH
authors.lastname: Xia
mesh_terms: D000818:Animals; D005073:Evoked Potentials, Somatosensory; D006041:Goats; D007431:Intraoperative Complications / Q000209:etiology / Q000517:prevention & control; D008279:Magnetic Resonance Imaging; D023421:Models, Animal; D010027:Osteotomy; D011183:Postoperative Complications / Q000209:etiology / Q000517:prevention & control; D013121:Spinal Curvatures / Q000601:surgery; D013904:Thoracic Vertebrae / Q000473:pathology* / Q000601:surgery*