title: Deviation analysis of C1-C2 transarticular screw placement assisted by a novel rapid prototyping drill template: a cadaveric study.
abstract: METHODS
  Cadaveric study.
  
  
  OBJECTIVE
  The aim of this study was to develop and validate the accuracy of a novel navigational template for C1-C2 transarticular screw (C1C2TAS) placement in cadaveric specimens.
  
  
  BACKGROUND
  Currently, C1C2TASs are primarily positioned using a free-hand technique or under fluoroscopic guidance. Screw placement is challenging owing to the small size of the C2 isthmus, which places technical demands on the surgeon. Screw insertion carries a potential risk of neurovascular injury, magnifying the importance of using a precise technique for screw insertion.
  
  
  METHODS
  Computed tomography (CT) scans with 0.625-mm wide cuts were obtained from the 32 cadaveric cervical specimens. The CT data were imported into a computer navigation system. We developed 32 three-dimensional drill templates, which were created by computer modeling using a rapid prototyping technique based on the CT data. We constructed drill templates using a custom trajectory for each level and side based on specimen anatomy. The drill templates were used to guide establishment of a pilot hole for screw placement. The entry point and angular direction of the intended screw positions and inserted screw positions were measured by comparing postoperative and preoperative images after the coordinate axes were synchronized.
  
  
  RESULTS
  The average displacement of the entry point of the left and right C1C2TAS in the x-, y-, and z-axis was 0.13±0.90 mm, 0.50±1.50 mm, and -0.22±0.71 mm on the left, and 0.21±1.03 mm, 0.46±1.55 mm, and -0.29±0.58 mm on the right. There was no statistically significant difference in entry point and direction between the intended and actual screw trajectory.
  
  
  CONCLUSIONS
  The small deviations seen are likely due to human error in the form of small variations in the surgical technique and use of software to design the prototype. This technology improves the safety profile of this fixation technique and should be further studied in clinical applications.
authors: *Department of Spinal Surgery, Ningbo No. 6 Hospital, Zhejiang Province, China †Department of Orthopaedic Surgery, Thomas Jefferson University & Rothman Institute, Philadelphia, PA ‡Institute of Biomedical Manufacturing and Life Quality Engineering, School of Mechanical and Power Energy Engineering, Shanghai Jiaotong University, Shanghai, China.
authors: Yong
authors: Y
authors: Hu
authors: Zhen-Shan
authors: ZS
authors: Yuan
authors: Christopher K
authors: CK
authors: Kepler
authors: Todd J
authors: TJ
authors: Albert
authors: Jian-Bing
authors: JB
authors: Yuan
authors: Wei-Xin
authors: WX
authors: Dong
authors: Xiao-Yang
authors: XY
authors: Sun
authors: Cheng-Tao
authors: CT
authors: Wang
mesh_terms: D000328:Adult; D001368:Axis, Cervical Vertebra / Q000000981:diagnostic imaging* / Q000601:surgery*; D001863:Bone Screws; D002102:Cadaver; D001270:Cervical Atlas / Q000000981:diagnostic imaging* / Q000601:surgery*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000601:surgery; D008297:Male; D008875:Middle Aged; D012984:Software; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D025321:Surgery, Computer-Assisted / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*