title: In vitro study of biomechanical behavior of anterior and transforaminal lumbar interbody instrumentation techniques.
abstract: OBJECTIVE
  To study the biomechanical behavior of lumbar interbody instrumentation techniques using titanium cages as either transforaminal lumbar interbody fusion (TLIF) or anterior lumbar interbody fusion (ALIF), with and without posterior pedicle fixation.
  
  
  METHODS
  Six fresh-frozen lumbar spines (L1-L5) were loaded with pure moments of +/-7.5 Nm in unconstrained flexion-extension, lateral bending, and axial rotation. Specimen were tested intact, after implantation of an ALIF or TLIF cage "stand-alone" in L2-L3 or L3-L4, and after additional posterior pedicle screw fixation.
  
  
  RESULTS
  In all loading directions, the range of motion (ROM) of the segments instrumented with cage and pedicle screw fixation was below the ROM of the intact lumbar specimen for both instrumentation techniques. A significant difference was found between the TLIF cage and the ALIF cage with posterior pedicle screw fixation for the ROM in flexion-extension and axial rotation (P < 0.05). Without pedicle screw fixation, the TLIF cage showed a significantly increased ROM and neutral zone compared with an ALIF cage "stand-alone" in two of the three loading directions (P < 0.05).
  
  
  CONCLUSIONS
  With pedicle screw fixation, the ALIF cage provides a higher segmental stability than the TLIF cage in flexion-extension and axial rotation, but the absolute biomechanical differences are minor. The different cage design and approach show only minor differences of segmental stability when combined with posterior pedicle screw fixation.
authors.affiliation: Spine Service, Department of Orthopaedic Surgery, University Hospital Tübingen, Tübingen, Germany. thomas.niemeyer@med.uni-tuebingen.de
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Niemeyer
authors.forename: Marco
authors.initials: M
authors.lastname: Koriller
authors.forename: Lutz
authors.initials: L
authors.lastname: Claes
authors.forename: Annette
authors.initials: A
authors.lastname: Kettler
authors.forename: Kathrin
authors.initials: K
authors.lastname: Werner
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Wilke
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena / Q000379:methods; D001860:Bone Plates; D001863:Bone Screws; D002102:Cadaver; D004548:Elasticity; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D066298:In Vitro Techniques; D008159:Lumbar Vertebrae / Q000503:physiopathology* / Q000601:surgery*; D008875:Middle Aged; D016059:Range of Motion, Articular; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods*; D013314:Stress, Mechanical