title: Optimal cervical screw insertion angle determined by means of computed tomography scans pre- and postoperatively.
abstract: Cervical pedicle screw (CPS) insertion is technically demanding and carries a risk of serious neurovascular complications when screws perforate. To avoid such serious risks, we currently perform CPS insertion using a computed tomography (CT)-guided navigation system. However, there remains a low probability of screw perforation during CPS insertion that is affected by factors such as CPS insertion angle and anatomical pedicle transverse angle (PTA).
  
  
  
  This study aimed to understand the perforation tendencies of CPS insertion angles in relation to anatomical PTA.
  
  
  
  This is a retrospective chart review.
  
  
  
  The study enrolled 151 consecutive patients (95 men and 56 women, with a mean age of 64.6 years).
  
  
  
  Anatomical PTA and CPS insertion angles were evaluated by axial CT images.
  
  
  
  The medical records of 151 consecutive patients who underwent CPS insertion using a CT-based navigation system were reviewed. We examined the relationships between PTA and CPS insertion angle on axial CT images according to vertebral level.
  
  
  
  The average preoperative PTA at each vertebral level was 32.1° for C2, 41.5° for C3, 41.0° for C4, 39.4° for C5, 34.4° for C6, and 27.3° for C7. Corresponding CT-determined pedicle screw insertion angles were 24.9°, 31.3°, 28.7°, 27.8°, 28.0°, and 26.0°, respectively. The CPS insertion angles at C2-C6 were significantly smaller than those for PTA (p<.01). In evaluations of angle thresholds from C3 to C5 that predicted a higher risk of perforation, the receiver operating characteristic curve analysis determined CPS insertion angles of <24.5° and >36.5° for the identification of lateral and medial perforations, respectively.
  
  
  
  For CPS insertion into the C3-C5 pedicles using CT, there is an increased likelihood of lateral or medial perforation for insertion angles of <24.5° or >36.5°, respectively.
authors.affiliation: Department of Orthopaedic Surgery, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto City, Nagano 390-8621, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Uehara
authors.affiliation: Department of Orthopaedic Surgery, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto City, Nagano 390-8621, Japan. Electronic address: jtaka@shinshu-u.ac.jp.
authors.forename: Jun
authors.initials: J
authors.lastname: Takahashi
authors.affiliation: Department of Orthopaedic Surgery, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto City, Nagano 390-8621, Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Ikegami
authors.affiliation: Department of Orthopaedic Surgery, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto City, Nagano 390-8621, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hashidate
authors.affiliation: Department of Orthopaedic Surgery, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto City, Nagano 390-8621, Japan.
authors.forename: Shugo
authors.initials: S
authors.lastname: Kuraishi
authors.affiliation: Department of Orthopaedic Surgery, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto City, Nagano 390-8621, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Shimizu
authors.affiliation: Department of Orthopaedic Surgery, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto City, Nagano 390-8621, Japan.
authors.forename: Toshimasa
authors.initials: T
authors.lastname: Futatsugi
authors.affiliation: Department of Orthopaedic Surgery, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto City, Nagano 390-8621, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Oba
authors.affiliation: Department of Orthopaedic Surgery, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto City, Nagano 390-8621, Japan.
authors.forename: Keijiro
authors.initials: K
authors.lastname: Mukaiyama
authors.affiliation: Department of Orthopaedic Surgery, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto City, Nagano 390-8621, Japan.
authors.forename: Nobuhide
authors.initials: N
authors.lastname: Ogihara
authors.affiliation: Department of Orthopaedic Surgery, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto City, Nagano 390-8621, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Hirabayashi
authors.affiliation: Department of Orthopaedic Surgery, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto City, Nagano 390-8621, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kato
mesh_terms: D000328:Adult; D000368:Aged; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D065289:Pedicle Screws / Q000009:adverse effects*; D011183:Postoperative Complications; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000009:adverse effects / Q000379:methods*; D025321:Surgery, Computer-Assisted / Q000009:adverse effects / Q000379:methods*; D014057:Tomography, X-Ray Computed
keywords: CT-based navigation system; Cervical pedicle screw; Pedicle transverse angle; Perforation tendencies; Screw insertion angle; Screw perforation