title: Optimizing the effectiveness of a mechanical suture-based anulus fibrosus repair construct in an acute failure laboratory simulation.
abstract: METHODS
  In vitro comparative, laboratory experiments.
  
  
  OBJECTIVE
  This study developed a laboratory apparatus that measured resistance to failure using pressures similar to intradiscal pressure of a lumbar spinal disk. Various combinations of an anular repair device were compared.
  Herniated material of the intervertebral disk is removed during a lumbar discectomy; however, the defect in the anulus fibrosus remains and can provide a pathway for future herniation. Repairing the anulus fibrosus could mitigate this reherniation and improve patient outcomes.
  
  
  METHODS
  A pneumatic cylinder was used to increase the pressure of a sealed chamber until artificial nucleus pulposus material was expulsed through either a 3-mm circular (diameter) or a 6-mm slit anular defect created in a surrogate anulus fibrosus. Each unrepaired condition was compared with 3 repaired conditions using a commercially available soft tissue repair system. The repaired conditions included: (1) a single tension band; (2) 2 tension bands in a cruciate pattern; or (3) 2 tension bands in a parallel pattern. Maximum pressure at the point of extrusion of the internal chamber material and failure or nonfailure of the repair was measured.
  
  
  RESULTS
  Significant differences were detected (P<0.05) in maximum failure pressures for the nonrepaired (control) versus repaired conditions. With 1 or 2 tension bands repairing the circular defect, the maximum failure pressure increased by approximately 76% and 131%, respectively. In addition, the failure pressure for 2 tension bands in either a cruciate or parallel configuration was not different, and was approximately 32% higher (P<0.05) than a single tension band in the case of the circular defect. Similar results were seen for the slit defect, with the exception that no difference between the repaired conditions (ie, single vs. 2 tension bands) was detected.
  
  
  CONCLUSIONS
  This laboratory simulation demonstrated that repairing the anulus fibrosus after a discectomy procedure can be beneficial for retaining intradiscal material. The use of 2 tension bands, versus a single tension band, in either a cruciate or parallel configuration may further improve the ability to retain disk material.
authors.affiliation: *Anulex Technologies Inc., Minnetonka MN †Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN.
authors.forename: Ashley
authors.initials: A
authors.lastname: Bartlett
authors.forename: Larry
authors.initials: L
authors.lastname: Wales
authors.forename: Rodney
authors.initials: R
authors.lastname: Houfburg
authors.forename: William K
authors.initials: WK
authors.lastname: Durfee
authors.forename: Steven L
authors.initials: SL
authors.lastname: Griffith
authors.forename: Ishmael
authors.initials: I
authors.lastname: Bentley
mesh_terms: D017586:Diskectomy; D006801:Humans; D007403:Intervertebral Disc / Q000473:pathology*; D007405:Intervertebral Disc Displacement; D007753:Laboratories; D008159:Lumbar Vertebrae; D008954:Models, Biological; D011312:Pressure; D013314:Stress, Mechanical; D013537:Sutures; D014945:Wound Healing