title: A Novel Anterior Odontoid Screw Plate for C1-C3 Internal Fixation: An In Vitro Biomechanical Study.
abstract: METHODS
  A biomechanical in vitro study was performed using a standardized experimental protocol in a biomechanical spine testing apparatus.
  
  
  OBJECTIVE
  The aims of this study were to evaluate the biomechanical stability afforded by 4 cervical fixation techniques: anterior cervical plate+odontoid screw+cage (ACP+OS+cage), anterior odontoid screw plate+bone graft (AOSP+bone graft), posterior C2-3 fixation+odontoid screw (C2PS+C3LMS+OS), and posterior C1-3 fixation (C1PS+C2PS+C3LMS).
  
  
  BACKGROUND
  Unstable axis injuries with multiple fracture lines are uncommon injuries, and their management is still challenging for surgeons who aim to achieve primary stability, early mobilization, preserved cervical range of motion (ROM), and favorable outcome. We designed a novel AOSP to assist in this challenging clinical scenario.
  
  
  METHODS
  Eight fresh-frozen cadaveric spine specimens (C1-C3) were subjected to stepwise destabilization of the C1-3 complex, with serial replication of a type II Hangman fracture, a type II odontoid fracture, and a C2 to C3 disc injury. Intact specimens, destabilized specimens, and destabilized specimens with various stabilization techniques including anterior and posterior techniques, some using our AOSP, were each tested for stability. Each spine was subjected to flexion, and extension testing, left and right lateral bending, and left and right rotation.
  
  
  RESULTS
  After AOSP+bone graft fixation, the ROMC2-C3 during all loading modes were reduced to values that were significantly less than normal. During all loading modes, AOSP+bone graft fixation significantly outperformed the ACP+OS+cage fixation in limiting ROMC2-C3. During flexion and extension, AOSP+bone graft fixation significantly outperformed the C1PS+C2PS+C3LMS fixation and C2PS+C3LMS+OS fixation in limiting ROMC2-C3.
  
  
  CONCLUSIONS
  The AOSP has excellent biomechanical performance when dealing with type I Hangman fractures, type II odontoid fractures, and C2-3 disc injuries. The AOSP+one graft fixation can preserve the function of atlanto-axial joint, which may be a valuable stabilization strategy for these unique injuries.
authors.affiliation: *Department of Spinal Surgery, Ningbo No. 6 Hospital, Zhejiang Province, PR China†Department of Orthopaedic Surgery, Thomas Jefferson University & Rothman Institute, Philadelphia, Pennsylvania.
authors.forename: Yong
authors.initials: Y
authors.lastname: Hu
authors.forename: Wei-xin
authors.initials: WX
authors.lastname: Dong
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Kepler
authors.forename: Zhen-shan
authors.initials: ZS
authors.lastname: Yuan
authors.forename: Xiao-yang
authors.initials: XY
authors.lastname: Sun
authors.forename: Jiao
authors.initials: J
authors.lastname: Zhang
authors.forename: Hui
authors.initials: H
authors.lastname: Xie
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D016025:Bone Transplantation; D002102:Cadaver; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008422:Materials Testing; D009809:Odontoid Process / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D011474:Prosthesis Design; D011859:Radiography; D016059:Range of Motion, Articular; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods; D013314:Stress, Mechanical