title: Biomechanical and in vivo evaluation of experimental closure devices of the annulus fibrosus designed for a goat nucleus replacement model.
abstract: Promising strategies are being developed to replace or regenerate the herniated nucleus pulposus. However, clinical efficacy of these methods has still to be addressed, and the lack of appropriate annulus closure techniques is increasingly being recognised as a major limiting factor. In the current study, in vitro and in vivo evaluation of novel annulus closure devices (ACDs) was performed. These devices are intended to be used in adjunct to nucleus replacement therapies in an experimental goat study. After a standardised discectomy had been performed, different ACDs were implanted solely or in addition to a collagen nucleus replacement implant. Biomechanical effects and axial failure load were assessed in vitro and followed by in vivo evaluation in a goat model. On axial compression, the average axial failure load for ACDs with four barb rings was significantly higher compared to the implants with five barb rings. The increased range of flexion-extension and latero-flexion observed after discectomy were restored to the normal range after implantation of the implants. Positive findings with the four-ring ACD were confirmed in goats after a follow-up of 2 weeks in vivo. However, after 6 weeks most implants (n = 16) showed signs of destruction and displacement. Although there seemed to be a tendency towards better results when ACDs were placed in addition to the nucleus replacements, these differences were not statistically significant. Moreover, two endplate reactions extending into the subchondral bone were observed, most likely due to continuous friction between the ACD and the vertebrae. Although current results are encouraging first steps towards the development of an efficient ACD for animal models, further optimisation is necessary. Current results also show that one cannot rely on in vitro biomechanical studies with annulus closure techniques, and these should always be confirmed in vivo in a large animal model.
authors.affiliation: Department of Orthopaedic Surgery, VU University Medical Center, Postbox 7057, 1007 MB Amsterdam, The Netherlands.
authors.forename: Johannes L
authors.initials: JL
authors.lastname: Bron
authors.forename: Albert J
authors.initials: AJ
authors.lastname: van der Veen
authors.forename: Marco N
authors.initials: MN
authors.lastname: Helder
authors.forename: Barend J
authors.initials: BJ
authors.lastname: van Royen
authors.forename: Theodoor H
authors.initials: TH
authors.lastname: Smit
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D017586:Diskectomy / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006041:Goats; D007403:Intervertebral Disc / Q000503:physiopathology / Q000601:surgery*; D007405:Intervertebral Disc Displacement / Q000503:physiopathology / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000503:physiopathology / Q000601:surgery*; D016059:Range of Motion, Articular; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*
references.citation: J Orthop Res. 2009 May;27(5):620-6
references.pmid: 18991343
references.citation: J Clin Laser Med Surg. 2000 Feb;18(1):29-32
references.pmid: 11189109
references.citation: Eur Spine J. 2007 Mar;16(3):329-37
references.pmid: 16683121
references.citation: Front Biosci. 2008 Jan 01;13:1507-25
references.pmid: 17981645
references.citation: Eur Spine J. 2002 Apr;11(2):137-44
references.pmid: 11956920
references.citation: Eur Spine J. 2008 Sep;17(9):1131-48
references.pmid: 18584218
references.citation: Spine (Phila Pa 1976). 1999 Apr 15;24(8):755-62
references.pmid: 10222525
references.citation: Spine (Phila Pa 1976). 1986 Nov;11(9):914-27
references.pmid: 3824069
references.citation: J Bone Joint Surg Am. 1964 Jul;46:1077-92
references.pmid: 14193834
references.citation: Med Hypotheses. 2008;70(2):361-8
references.pmid: 17624684
references.citation: Clin Orthop Relat Res. 2005 Nov;440:149-56
references.pmid: 16239799
references.citation: J Orthop Res. 2006 Jun;24(6):1292-8
references.pmid: 16649177
references.citation: Orthop Clin North Am. 2007 Jul;38(3):363-72; abstract vi
references.pmid: 17629984
references.citation: Spine J. 2005 Jan-Feb;5(1):85-94
references.pmid: 15653089
references.citation: Annu Int Conf IEEE Eng Med Biol Soc. 2007;2007:6401-6
references.pmid: 18003487
references.citation: Acta Orthop Scand. 1965;35:314-28
references.pmid: 14295432
references.citation: J Bone Joint Surg Am. 2003 Jan;85(1):102-8
references.pmid: 12533579
references.citation: Eur Spine J. 2006 Aug;15 Suppl 3:S433-8
references.pmid: 16868784
references.citation: Eur Spine J. 2009 Mar;18(3):301-13
references.pmid: 19104850
references.citation: J Neurosurg Spine. 2008 Sep;9(3):307-13
references.pmid: 18928230
references.citation: Spine (Phila Pa 1976). 2000 Sep 1;25(17):2165-70
references.pmid: 10973397