title: [Clinical significance of thoracic pedicle classification by inner cortical width of pedicles on CT images in posterior vertebral column resection for treatment of rigid and severe spinal deformities].
abstract: OBJECTIVE
  To investigate the clinical significances of the thoracic pedicle classification determined by inner cortical width of pedicle in posterior vertebral column resection (PVCR) with free hand technique for the treatment of rigid and severe spinal deformities.
  
  
  METHODS
  Between October 2004 and July 2010, 56 patients with rigid and severe spinal deformities underwent PVCR. A total of 1098 screws were inserted into thoracic pedicles at T(2-12). The inner cortical width of the thoracic pedicle was measured and divided into 4 groups: group 1 (0-1.0 mm), group 2 (1.1-2.0 mm), group 3 (2.1-3.0 mm), and group 4 (> 3.1 mm). The success rate of screw-insertion into the thoracic pedicles was analyzed statistically. A new 3 groups was divided according to the statistical results and the success rate of screw-insertion into the thoracic pedicles was analyzed statistically again. And statistical analysis was performed between different types of thoracic pedicles classification for pedicle morphological method by Lenke.
  
  
  RESULTS
  There were significant differences in the success rate of screw-insertion between the other groups (P < 0.008) except between group 3 and group 4 (chi2 = 2.540, P = 0.111). The success rates of screw-insertion were 35.05% in group 1, 65.34% in group 2, and 88.32% in group 3, showing significant differences among 3 groups (P < 0.017). According to Lenke classification, the success rates of screw-insertion were 82.31% in type A, 83.40% in type B, 80.00% in type C, and 30.28% in type D, showing no significant differences (P > 0.008) among types A, B, and C except between type D and other 3 types (P < 0.008). In the present study, regarding the distribution of different types of thoracic pedicles, types I, II a, and II b thoracic pedicles accounted for 17.67%, 16.03%, and 66.30% of the total thoracic pedicles, respectively. The type I, II a, and II b thoracic pedicles at the concave side accounted for 24.59%, 21.13%, and 54.28%, and at the convex side accounted for 10.75%, 10.93%, and 78.32%, respectively.
  
  
  CONCLUSIONS
  A quantification classification standard of thoracic pedicles is presented according to the inner cortical width of the pedicle on CT imaging: type I thoracic pedicle, an absent channel with an inner cortical width of 0-1.0 mm; type II thoracic pedicle, a channel, including type IIa thoracic pedicle with an inner cortical width of 1.1-2.0 mm, and type IIb thoracic pedicle with an inner cortical width more than 2.1 mm. The thoracic pedicle classification method has high prediction accuracy of screw-insertion when PVCR is performed.
authors.affiliation: Department of Orthopaedics, Second Affiliated Hospital of Kunming Medical College, Kunming Yunnan 650101, PR China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jingming
authors.initials: J
authors.lastname: Xie
authors.forename: Yingsong
authors.initials: Y
authors.lastname: Wang
authors.forename: Ni
authors.initials: N
authors.lastname: Bi
authors.forename: Zhi
authors.initials: Z
authors.lastname: Zhao
authors.forename: Tao
authors.initials: T
authors.lastname: Li
mesh_terms: D000293:Adolescent; D000328:Adult; D001863:Bone Screws; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures; D013122:Spinal Diseases / Q000145:classification* / Q000000981:diagnostic imaging* / Q000601:surgery; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult