title: In vitro stabilizing effect of a transforaminal compared with two posterior lumbar interbody fusion cages.
abstract: METHODS
  An in vitro biomechanical flexibility test on different lumbar interbody fusion cages using monosegmental lumbar spine specimens.
  
  
  OBJECTIVE
  To investigate the stabilizing effect of a transforaminal lumbar interbody fusion (TLIF) cage compared with two established posterior lumbar interbody fusion (PLIF) cages.
  
  
  BACKGROUND
  TLIF using interbody fusion cages is gaining more and more popularity in the treatment of degenerative disc disease. However, only little is known on its biomechanical behavior.
  
  
  METHODS
  Eighteen intact human lumbar spine segments were tested for flexibility in a specially designed spine tester. Pure moments were applied in the three main planes, and range of motion and neutral zone were determined. Then, TLIF using the sickle-shaped MOON cage (AMT AG), PLIF using the cubic Stryker cages (Stryker Orthopaedics), or PLIF using the threaded BAK cages (Zimmer Spinetech) was carried out and the specimens tested again.
  
  
  RESULTS
  The stability after implantation of the MOON TLIF cage did not significantly differ from that after implantation of the cubic Stryker PLIF cages (P > 0.05). In contrast, the threaded BAK PLIF cages had a significantly higher primary stability than both the MOON TLIF and the Stryker PLIF cages in lateral bending, flexion, and extension (P < 0.05) but not in axial rotation (P > 0.05).
  
  
  CONCLUSIONS
  In terms of its stabilizing effect, TLIF using the MOON cage can be recommended as an alternative to PLIF using the cubic Stryker cages. Compared with the threaded BAK PLIF cages, however, the MOON TLIF cage provides a lower primary stability in lateral bending, flexion, and extension.
authors.affiliation: Department Unfallchirurgische Forschung und Biomechanik, Universitat Ulm, Ulm, Germany.
authors.forename: Annette
authors.initials: A
authors.lastname: Kettler
authors.forename: Werner
authors.initials: W
authors.lastname: Schmoelz
authors.forename: Erich
authors.initials: E
authors.lastname: Kast
authors.forename: Maria
authors.initials: M
authors.lastname: Gottwald
authors.forename: Lutz
authors.initials: L
authors.lastname: Claes
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Wilke
mesh_terms: D001577:Benzophenones; D001672:Biocompatible Materials; D001696:Biomechanical Phenomena; D006801:Humans; D066298:In Vitro Techniques; D007659:Ketones; D008159:Lumbar Vertebrae / Q000502:physiology* / Q000601:surgery*; D008422:Materials Testing; D011092:Polyethylene Glycols; D011108:Polymers; D016059:Range of Motion, Articular; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods*
chemical_list: D001577:Benzophenones; D001672:Biocompatible Materials; D007659:Ketones; D011108:Polymers; C063834:polyetheretherketone; D011092:Polyethylene Glycols