title: [Pullout test in expansive unilateral open-door laminoplasty of the cervical spine with OsteoMed M3 plate and screws: the screw orientation matters].
abstract: OBJECTIVE
  To study the impact of screw orientation on the pullout strength of OsteoMed M3 titanium screws in expansive unilateral open-door laminoplasty of the cervical spine.
  
  
  METHODS
  Six fresh human cervical spine specimens were randomly numbered and OsteoMed M3 plate and screws were used for an expansive unilateral open-door laminoplasty. The screws were inserted in the lateral mass at different extraversion angles (0°, 30° and 45°). The maximum pullout strength was tested on the ElectroForce material testing machine.
  
  
  RESULTS
  The maximum pullout strength was 81.60∓7.33 N, 150.05∓15.57 N, and 160.08∓17.77 N in extraversion angle 0°, 30°, and 45° groups, respectively. The maximum pullout strength was significantly less in extraversion angle 0° group than in 30° and 45° groups (P<0.05), but similar in the latter two groups.
  
  
  CONCLUSIONS
  The pullout strength of the screws inserted at an extraversion angle over 30° provides stronger fixation than an angle of 0° in the unilateral open-door laminoplasty using OsteoMed M3 titanium plate and screws.
authors: Department of Orthopedics, Zhujiang Hospital, Southern Medical University, Guangzhou 510282, China. hkhgksq@126.com
authors: Kong-he
authors: KH
authors: Hu
authors: An-min
authors: AM
authors: Jin
authors: Yang
authors: Y
authors: Duan
authors: Cheng-long
authors: CL
authors: Liu
authors: Shao-xiong
authors: SX
authors: Min
authors: Li-xin
authors: LX
authors: Zhu
authors: Wei-dong
authors: WD
authors: Zhao