title: Screw perforation features in 129 consecutive patients performed computer-guided cervical pedicle screw insertion.
abstract: METHODS
  A cross-sectional study of the data retrospectively collected by chart review.
  
  
  OBJECTIVE
  This study aimed to clarify screw perforation features in 129 consecutive patients treated with computer-assisted cervical pedicle screw (CPS) insertion and to determine important considerations for computer-assisted CPS insertion. CPS fixation has been criticized for the potential risk of serious injury to neurovascular structures. To avoid such serious risks, computed tomography (CT)-based navigation has been used during CPS insertion, but screw perforation can occur even with the use of a navigation system.
  
  
  METHODS
  The records of 129 consecutive patients who underwent cervical (C2-C7) pedicle screw insertion using a CT-based navigation system from September 1997 to August 2013 were reviewed. Postoperative CT images were used to evaluate the accuracy of screw placement. The screw insertion status was classified as grade 1 (no perforation), indicating that the screw was accurately inserted in pedicle; grade 2 (minor perforation), indicating perforation of less than 50 % of the screw diameter; and grade 3 (major perforation), indicating perforation of 50 % or more of the screw diameter. We analyzed the direction and rate of screw perforation according to the vertebral level.
  
  
  RESULTS
  The rate of grade 3 pedicle screw perforations was 6.7 % (39/579), whereas the combined rate of grades 2 and 3 perforations was 20.0 % (116/579). No clinically significant complications, such as vertebral artery injury, spinal cord injury, or nerve root injury, were caused by the screw perforations. Of the screws showing grade 3 perforation, 30.8 % screws were medially perforated and 69.2 % screws were laterally perforated. Of the screws showing grades 2 and 3 perforation, 21.6 % screws were medially perforated and 78.4 % screws were laterally perforated. Furthermore, we evaluated screw perforation rates according to the vertebral level. Grade 3 pedicle screw perforation occurred in 6.1 % of C2 screws; 7.5 % of C3 screws; 13.0 % of C4 screws; 6.5 % of C5 screws; 3.2 % of C6 screws; and 4.0 % of C7 screws. Grades 2 and 3 pedicle screw perforations occurred in 12.1 % of C2 screws, 22.6 % of C3 screws, 31.5 % of C4 screws, 22.2 % of C5 screws, 14.4 % of C6 screws, and 12.1 % of C7 screws. C3-5 screw perforation rate was significantly higher than C6-7 (p = 0.0024).
  
  
  CONCLUSIONS
  Careful insertion of pedicle screws is necessary, especially at C3 to C5, even when using a CT-based navigation system. Pedicle screws tend to be laterally perforated.
authors.affiliation: Department of Orthopaedic Surgery, Yodakubo Hospital, 2857 Furumachi, Nagawamachi, Chiisagatagun, Nagano, 386-0603, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Uehara
authors.forename: Jun
authors.initials: J
authors.lastname: Takahashi
authors.forename: Shota
authors.initials: S
authors.lastname: Ikegami
authors.forename: Keijiro
authors.initials: K
authors.lastname: Mukaiyama
authors.forename: Shugo
authors.initials: S
authors.lastname: Kuraishi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Shimizu
authors.forename: Toshimasa
authors.initials: T
authors.lastname: Futatsugi
authors.forename: Nobuhide
authors.initials: N
authors.lastname: Ogihara
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hashidate
authors.forename: Hiroki
authors.initials: H
authors.lastname: Hirabayashi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kato
mesh_terms: D000328:Adult; D000368:Aged; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000293:injuries* / Q000601:surgery*; D003430:Cross-Sectional Studies; D019299:Decompression, Surgical / Q000009:adverse effects / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D065289:Pedicle Screws / Q000009:adverse effects*; D011184:Postoperative Period; D011843:Radiculopathy / Q000209:etiology / Q000517:prevention & control; D012189:Retrospective Studies; D013119:Spinal Cord Injuries / Q000209:etiology* / Q000517:prevention & control; D013122:Spinal Diseases / Q000000981:diagnostic imaging / Q000601:surgery*; D025321:Surgery, Computer-Assisted / Q000009:adverse effects* / Q000379:methods; D014057:Tomography, X-Ray Computed
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