title: Posterior-only stabilization of 2-column and 3-column injuries at the cervicothoracic junction: a biomechanical study.
abstract: METHODS
  A biomechanical study conducted on cadaveric specimens.
  
  
  OBJECTIVE
  The objectives of the study were (1) to determine whether a 3-column injury at the cervicothoracic junction may be stabilized with only posterior instrumentation and (2) to determine optimal cross-link position.
  
  
  BACKGROUND
  Previous literature has suggested that 3-column cervicothoracic injury requires both anterior and posterior instrumentation to restore spinal stability.
  
  
  METHODS
  Multidirectional flexibility analysis was performed under axial rotation, flexion extension, and lateral bending. After intact analysis, C7-T1 was destabilized simulating a 2-column injury and specimens instrumented from C6-T2 with lateral mass (C6) and pedicle (C7-T2) screws using dual diameter rods and retested. C7-T1 was further destabilized to a 3-column injury and specimens retested once again. The addition of a cross-link in either the cervical, thoracic, or combined positions was also analyzed. Range of motion (ROM) at C7-T1 and of the whole construct was recorded using optoelectronic markers and data normalized to intact condition (% intact). Statistical significance criterion was set at P<0.05.
  
  
  RESULTS
  Greater than 75% reduction of intact ROM was achieved after posterior-only instrumentation of a 3-column injury (P<0.05) using modern instrumentation and technique. For a 2-column injury, no significant difference (P>0.05) was found with or without cross-links. ROM at C7-T1 was effectively reduced by 85% or more compared with intact preinjury motion in all planes. A trend toward increased stability at C7-T1 was noted from the application of a thoracic cross-link versus a cervical cross-link.
  
  
  CONCLUSIONS
  A 3-column injury at the cervicothoracic junction may be stabilized from a biomechanical standpoint using posterior-only instrumentation. The addition of 2 cross-links further stabilizes the cervicothoracic junction in a 3-column injury. A thoracic cross-link was not significantly different from 2 cross-links. The use of a cross-link in 2-column flexion distraction injuries at the cervicothoracic junction may be unnecessary.
authors.affiliation: Department of Orthopaedic Surgery, George Washington University, WA, DC 20037, USA. jobrien@mfa.gwu.edu
authors.forename: Joseph R
authors.initials: JR
authors.lastname: O'Brien
authors.forename: Anton E
authors.initials: AE
authors.lastname: Dmitriev
authors.forename: Warren
authors.initials: W
authors.lastname: Yu
authors.forename: Daniel
authors.initials: D
authors.lastname: Gelb
authors.forename: Steven
authors.initials: S
authors.lastname: Ludwig
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology; D001863:Bone Screws / Q000009:adverse effects / Q000592:standards; D002102:Cadaver; D002574:Cervical Vertebrae / Q000293:injuries / Q000473:pathology / Q000601:surgery*; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D016268:Internal Fixators / Q000009:adverse effects* / Q000592:standards; D008297:Male; D017063:Outcome Assessment, Health Care / Q000379:methods; D011183:Postoperative Complications / Q000473:pathology / Q000503:physiopathology* / Q000517:prevention & control; D016059:Range of Motion, Articular / Q000502:physiology; D013123:Spinal Fusion / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods; D013124:Spinal Injuries / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D013904:Thoracic Vertebrae / Q000293:injuries / Q000473:pathology / Q000601:surgery*; D016474:Weight-Bearing / Q000502:physiology