title: Biomechanical analysis of a novel hook-screw technique for C1-2 stabilization.
abstract: The Food and Drug Administration has not cleared the following medical devices for the use described in this study. The following medical devices are being discussed for an off-label use: cervical lateral mass screws.
  
  
  OBJECTIVE
  As an alternative for cases in which the anatomy and spatial relationship between C-2 and a vertebral artery precludes insertion of C-2 pedicle/pars or C1-2 transarticular screws, a technique that includes opposing laminar hooks (claw) at C-2 combined with C-1 lateral mass screws may be used. The biomechanical stability of this alternate technique was compared with that of a standard screw-rod technique in vitro.
  
  
  METHODS
  Flexibility tests were performed in 7 specimens (occiput to C-3) in the following 6 different conditions: 1) intact; 2) after creating instability and attaching a posterior cable/graft at C1-2; 3) after removing the graft and attaching a construct comprising C-1 lateral mass screws and C-2 laminar claws; 4) after reattaching the posterior cable-graft at C1-2 (posterior hardware still in place); 5) after removing the posterior cable-graft and laminar hooks and placing C-2 pedicle screws interconnected to C-1 lateral mass screws via rod; and 6) after reattaching the posterior cable-graft at C1-2 (screw-rod construct still in place).
  
  
  RESULTS
  All types of stabilization significantly reduced the range of motion, lax zone, and stiff zone compared with the intact condition. There was no significant biomechanical difference in terms of range of motion or lax zone between the screw-rod construct and the screw-claw-rod construct in any direction of loading.
  
  
  CONCLUSIONS
  The screw-claw-rod technique restricts motion much like the standard Harms technique, making it an acceptable alternative technique when aberrant arterial anatomy precludes the placement of C-2 pars/pedicle screws or C1-2 transarticular screws.
authors: Spinal Biomechanics Laboratory, Department of Neurosurgery Research, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona 85013, USA.
authors: Marco Túlio
authors: MT
authors: Reis
authors: Eric W
authors: EW
authors: Nottmeier
authors: Phillip M
authors: PM
authors: Reyes
authors: Seungwon
authors: S
authors: Baek
authors: Neil R
authors: NR
authors: Crawford
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D001863:Bone Screws; D016025:Bone Transplantation; D001270:Cervical Atlas / Q000601:surgery*; D002574:Cervical Vertebrae / Q000601:surgery*; D018795:Device Approval; D004867:Equipment Design; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D009777:Occipital Bone / Q000601:surgery; D009809:Odontoid Process / Q000601:surgery*; D056687:Off-Label Use; D018583:Pliability; D013123:Spinal Fusion / Q000295:instrumentation*; D014481:United States; D014486:United States Food and Drug Administration