title: Deviation analysis of atlantoaxial pedicle screws assisted by a drill template.
abstract: Although C1-C2 pedicle screw fixation provides an excellent fusion rate and rigid fixation, this technique has a potential risk. It is essential to develop an accurate screwing method to avoid this neurovascular injury. To develop and validate the accuracy of a novel navigational template for C1-C2 pedicle screw placement in cadaveric specimens, computed tomography scans with 1-mm-wide cuts were obtained of 32 cadaveric cervical specimens. The authors developed 64 three-dimensional full-scale templates that were created by computer modeling with a rapid prototyping technique from the computed tomography data. Drill templates were constructed with a custom trajectory for each level and side. The drill templates were used to guide the establishment of a pilot hole for screw placement. The average distances between ideal and actual entry points of the C1 pedicle screws in the x, y, and z axes were 0.16±0.46 mm, 0.11±0.52 mm, and -0.01±0.54 mm, respectively, on the left side and 0.11±0.49 mm, 0.01±0.56 mm, and -0.09±0.59 mm, respectively, on the right side. The average distances between ideal and actual entry points of the C2 pedicle screws in the x, y, and z axes were 0.05±0.54 mm, 0.20±0.59 mm, and -0.06±0.58 mm, respectively, on the left side and 0.17±0.55 mm, 0.1±0.58 mm, and -0.01±0.49 mm, respectively, on the right side. Factors related to human error and imprecision are responsible for most malpositioning of instrumentation. The rapid prototyping drill template for C1-C2 screw placement is described to minimize human error, although it introduces error related to computer software and variation in manufacturing.
authors.forename: Yong
authors.initials: Y
authors.lastname: Hu
authors.forename: Zhen-Shan
authors.initials: ZS
authors.lastname: Yuan
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Kepler
authors.forename: Todd J
authors.initials: TJ
authors.lastname: Albert
authors.forename: Hui
authors.initials: H
authors.lastname: Xie
authors.forename: Jian-Bing
authors.initials: JB
authors.lastname: Yuan
authors.forename: Wei-Xin
authors.initials: WX
authors.lastname: Dong
authors.forename: Cheng-Tao
authors.initials: CT
authors.lastname: Wang
mesh_terms: D000328:Adult; D001863:Bone Screws; D002102:Cadaver; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013123:Spinal Fusion / Q000295:instrumentation*; D025321:Surgery, Computer-Assisted; D014057:Tomography, X-Ray Computed