title: Closure of the annulus fibrosus of the intervertebral disc using a novel suture application device-in vivo porcine and ex vivo biomechanical evaluation.
abstract: Defects in the annulus fibrosus (AF) remain a challenge in the surgical treatment of lumbar disc herniations with persistent defects, allowing potential re herniation of nucleus pulposus (NP) tissue. A cervical porcine model was chosen to simulate human lumbar intervertebral disc (IVD).
  
  
  
  The aim of this study was to determine the technical feasibility of closure of the AF of the IVD using a novel minimally invasive Kerrison-shaped suture application device.
  
  
  
  Ex vivo biomechanical and in vivo porcine device evaluations were performed.
  
  
  
  Ex vivo biomechanical evaluation: 15 porcine spinal units were explanted and subjected to mock discectomy. The annular defect was closed using 2-0 non-absorbable (ultra-high molecular-weight polyethylene, UHMWPE) suture and Dines knot. The knot was backed up with two, three, or four throws. The spinal unit was subject to 4000 cycles of flexion/extension with 1500 N of axial load, and assessed for knot slippage. In vivo porcine device evaluation: three pigs (53-57 kg) were anesthetized and underwent a ventral surgical approach to the cervical spine. The AF of two discs was incised, and simulated partial NP discectomy was performed. The defect was closed at one level using the AnchorKnot device to apply the suture with a Dines knot and four throws. The pigs were observed for 4 weeks before euthanasia, allowing 7T magnetic resonance imaging (MRI) and histological evaluation.
  
  
  
  A Dines knot with four throws experienced no slippage after 4000 cycles. This configuration was tested in vivo. Clinically, the neurological examination in treated pigs was normal following surgery. Histological and MRI assessment confirmed sustained defect closure at 4 weeks. There was no reaction to the suture material and no NP extrusion at any of the sutured levels.
  
  
  
  This study demonstrates that it is technically feasible to perform AF defect closure in a porcine model. This novel device achieved AF defect closure that was maintained through 4 weeks in vivo.
authors.affiliation: Sunnybrook Health Sciences Centre, 2075 Bayview Ave., Toronto, ON, M4N 3M5, Canada. Electronic address: abateman@doctors.org.uk.
authors.forename: Antony H
authors.initials: AH
authors.lastname: Bateman
authors.affiliation: Department of Kinesiology, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada.
authors.forename: Christian
authors.initials: C
authors.lastname: Balkovec
authors.affiliation: Techna Institute, University Health Network, 100 College St., Rm 211, Toronto, ON, M5G 1P5, Canada; Department of Medical Biophysics and Department of Surgery, University of Toronto, 101 College Street, ON, M5T 1L7, Canada.
authors.forename: Margarete K
authors.initials: MK
authors.lastname: Akens
authors.affiliation: Sunnybrook Health Sciences Centre, 2075 Bayview Ave., Toronto, ON, M4N 3M5, Canada.
authors.forename: Andrea H W
authors.initials: AH
authors.lastname: Chan
authors.affiliation: Anchor Orthopedics XT Inc., 2645 Matheson Blvd. East, Mississauga, ON, L4W 5S4, Canada.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Harrison
authors.affiliation: Sunnybrook Research Institute, 2075 Bayview Ave., Toronto, ON, M4N 3M5, Canada.
authors.forename: Wendy
authors.initials: W
authors.lastname: Oakden
authors.affiliation: Sunnybrook Health Sciences Centre, 2075 Bayview Ave., Toronto, ON, M4N 3M5, Canada.
authors.forename: Albert J M
authors.initials: AJ
authors.lastname: Yee
authors.affiliation: Department of Kinesiology, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada.
authors.forename: Stuart M
authors.initials: SM
authors.lastname: McGill
mesh_terms: D000818:Animals; D000070616:Annulus Fibrosus / Q000601:surgery*; D001696:Biomechanical Phenomena; D017586:Diskectomy / Q000295:instrumentation / Q000379:methods*; D013525:Surgical Instruments / Q000009:adverse effects*; D013537:Sutures / Q000009:adverse effects*; D013552:Swine
keywords: Annular repair; Annulus fibrosus closure; Disc repair; Discectomy; Intervertebral disc; Minimally invasive; Porcine model; Re-herniation; Surgery; Suture application device