title: Biomechanical analysis and review of lateral lumbar fusion constructs.
abstract: METHODS
  Biomechanical study and the review of literature on lumbar interbody fusion constructs.
  
  
  OBJECTIVE
  To demonstrate the comparative stabilizing effects of lateral interbody fusion with various supplemental internal fixation options.
  
  
  BACKGROUND
  Lumbar interbody fusion procedures are regularly performed using anterior, posterior, and more recently, lateral approaches. The biomechanical profile of each is determined by the extent of resection of local supportive structures, implant size and orientation, and the type of supplemental internal fixation used.
  
  
  METHODS
  Pure moment flexibility testing was performed using a custom-built 6 degree-of-freedom system to apply a moment of ±7.5 Nm in each motion plane, while motion segment kinematics were evaluated using an optoelectronic motion system. Constructs tested included the intact spine, stand-alone extreme lateral interbody implant, interbody implant with lateral plate, unilateral and bilateral pedicle screw fixation. These results were evaluated against those from literature-reported biomechanical studies of other lumbar interbody constructs.
  
  
  RESULTS
  All conditions demonstrated a statistically significant reduction in range of motion (ROM) as a percentage of intact. In flexion-extension, ROM was 31.6% stand-alone, 32.5% lateral fixation, and 20.4% and 13.0% unilateral and bilateral pedicle screw fixation, respectively. In lateral bending, the trend was similar with greater reduction with lateral fixation than in flexion-extension; ROM was 32.5% stand-alone, 15.9% lateral fixation, and 21.6% and 14.4% unilateral and bilateral pedicle screw fixation. ROM was greatest in axial rotation; 69.4% stand-alone, 53.4% lateral fixation, and 51.3% and 41.7% unilateral and bilateral pedicle screw fixation, respectively.
  
  
  CONCLUSIONS
  The extreme lateral interbody construct provided the largest stand-alone reduction in ROM compared with literature-reported ALIF and TLIF constructs. Supplemental bilateral pedicle screw-based fixation provided the overall greatest reduction in ROM, similar among all interbody approach techniques. Lateral fixation and unilateral pedicle screw fixation provided intermediate reductions in ROM. Clinically, surgeons may evaluate these comparative results to choose fixation options commensurate with the stability requirements of individual patients.
authors.affiliation: Buffalo Spine Surgery, Lockport, NY, USA. andycapp46@aol.com
authors.forename: Andrew
authors.initials: A
authors.lastname: Cappuccino
authors.forename: G Bryan
authors.initials: GB
authors.lastname: Cornwall
authors.forename: Alexander W L
authors.initials: AW
authors.lastname: Turner
authors.forename: Guy R
authors.initials: GR
authors.lastname: Fogel
authors.forename: Huy T
authors.initials: HT
authors.lastname: Duong
authors.forename: Kee D
authors.initials: KD
authors.lastname: Kim
authors.forename: Darrel S
authors.initials: DS
authors.lastname: Brodke
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena / Q000502:physiology; D001863:Bone Screws; D006801:Humans; D016268:Internal Fixators; D008159:Lumbar Vertebrae / Q000502:physiology* / Q000601:surgery*; D008875:Middle Aged; D018583:Pliability; D016059:Range of Motion, Articular / Q000502:physiology*; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D013314:Stress, Mechanical