Posterior motion preserving implants evaluated by means of intervertebral disc bulging and annular fiber strains



      The aims of motion preserving implants are to ensure sufficient stability to the spine, to release facet joints by also allowing a physiological loading to the intervertebral disc. The aim of this study was to assess disc load contribution by means of annular fiber strains and disc bulging of intact and stiffened segments. This was compared to the segments treated with various motion preserving implants.


      A laser scanning device was used to obtain three-dimensional disc bulging and annular fiber strains of six lumbar intervertebral discs (L2–3). Specimens were loaded with 500 N or 7.5 Nm moments in a spine tester. Each specimen was treated with four different implants; DSS™, internal fixator, Coflex™, and TOPS™.


      In axial compression, all implants performed in a similar way. In flexion, the Coflex decreased range of motion by 13%, whereas bulging and fiber strains were similar to intact. The DSS stabilized segments by 54% compared to intact. TOPS showed a slight decrease in fiber strains (5%) with a range of motion similar to intact. The rigid fixator allowed strains up to 2%. In lateral bending, TOPS yielded range of motion values similar to intact, but maximum fiber strains doubled from 6.5% (intact) to 13.8%. Coflex showed range of motion, bulging and strain values similar to intact. The DSS and the rigid fixator reduced these values. The implants produced only minor changes in axial rotation.


      This study introduces an in vitro method, which was employed to evaluate spinal implants other than standard biomechanical methods. We could demonstrate that dynamic stabilization methods are able to keep fiber strains and disc bulging in a physiological range.


      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to Clinical Biomechanics
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Adams M.A.
        • Dolan P.
        • Hutton W.C.
        The lumbar spine in backward bending.
        Spine. 1988; 13: 1019-1026
        • Christie S.D.
        • Song J.K.
        • Fessler R.G.
        Dynamic interspinous process technology.
        Spine. 2005; 30: S73-S78
        • Costi J.J.
        • Stokes I.A.
        • Gardner-Morse M.
        • Laible J.P.
        • Scoffone H.M.
        • Iatridis J.C.
        Direct measurement of intervertebral disc maximum shear strain in six degrees of freedom: Motions that place disc tissue at risk of injury.
        J. Biomech. 2007; 40: 2457-2466
        • Ebara S.
        • Iatridis J.C.
        • Setton L.A.
        • Foster R.J.
        • Mow V.C.
        • Weidenbaum M.
        Tensile properties of nondegenerate human lumbar anulus fibrosus.
        Spine. 1996; 21: 452-461
        • Galante J.O.
        Tensile properties of the human lumbar annulus fibrosus.
        Acta Orthop. Scand. Suppl. 1967; 100: 101-191
        • Heuer F.
        • Schmitt H.
        • Schmidt H.
        • Claes L.
        • Wilke H.J.
        Creep associated changes in intervertebral disc bulging obtained with a laser scanning device.
        Clin. Biomech. 2007; 22: 737-744
        • Heuer F.
        • Schmidt H.
        • Claes L.
        • Wilke H.J.
        A new laser scanning technique for imaging intervertebral disc displacement and its application to modeling nucleotomy.
        Clin. Biomech. 2008; 23: 260-269
        • Heuer F.
        • Schmidt H.
        • Wilke H.J.
        The relation between intervertebral disc bulging and annular fiber associated strains for simple and complex loading.
        J. Biomech. 2008; 41: 1086-1094
        • Heuer F.
        • Wolfram U.
        • Schmidt H.
        • Wilke H.J.
        A method to obtain surface strains of soft tissues using a laser scanning device.
        J. Biomech. 2008; 41: 2402-2410
        • Holzapfel G.A.
        • Schulze-Bauer C.A.
        • Feigl G.
        • Regitnig P.
        Single lamellar mechanics of the human lumbar anulus fibrosus.
        Biomech. Model. Mechanobiol. 2005; 3: 125-140
        • Hutton W.C.
        • Elmer W.A.
        • Boden S.D.
        • Hyon S.
        • Toribatake Y.
        • Tomita K.
        • et al.
        The effect of hydrostatic pressure on intervertebral disc metabolism.
        Spine. 1999; 24: 1507-1515
        • Iatridis J.C.
        • MaClean J.J.
        • Ryan D.A.
        Mechanical damage to the intervertebral disc annulus fibrosus subjected to tensile loading.
        J. Biomech. 2005; 38: 557-565
        • Lotz J.C.
        • Colliou O.K.
        • Chin J.R.
        • Duncan N.A.
        • Liebenberg E.
        Compression-induced degeneration of the intervertebral disc: an in vivo mouse model and finite-element study.
        Spine. 1998; 23: 2493-2506
        • Neidlinger-Wilke C.
        • Würtz K.
        • Schmidt C.
        • Blessing H.
        • Börm W.
        • Arand M.
        • et al.
        Effects of mechanical forces on intervertebral disc cells from annulus and nucleus of human and bovine discs.
        in: Combined Meeting of Leading Scientifig Spine Societies, Porto. 2004
        • Rannou F.
        • Richette P.
        • Benallaoua M.
        • Francois M.
        • Genries V.
        • Korwin-Zmijowska C.
        • et al.
        Cyclic tensile stretch modulates proteoglycan production by intervertebral disc annulus fibrosus cells through production of nitrite oxide.
        J. Cell. Biochem. 2003; 90: 148-157
        • Schmidt H.
        • Kettler A.
        • Heuer F.
        • Simon U.
        • Claes L.
        • Wilke H.J.
        Intradiscal pressure, shear strain, and fiber strain in the intervertebral disc under combined loading.
        Spine. 2007; 32: 748-755
        • Schmoelz W.
        • Huber J.F.
        • Nydegger T.
        • Claes L.
        • Wilke H.J.
        Dynamic stabilization of the lumbar spine and its effects on adjacent segments: an in vitro experiment.
        J. Spinal Disord. Tech. 2003; 16: 418-423
        • Seroussi R.E.
        • Krag M.H.
        • Muller D.L.
        • Pope M.H.
        Internal deformations of intact and denucleated human lumbar discs subjected to compression, flexion, and extension loads.
        J. Orthop. Res. 1989; 7: 122-131
        • Shah J.S.
        • Hampson W.G.
        • Jayson M.I.
        The distribution of surface strain in the cadaveric lumbar spine.
        J. Bone Joint Surg. (Br. Ed.). 1978; 60-B: 246-251
        • Stoll T.M.
        • Dubois G.
        • Schwarzenbach O.
        The dynamic neutralization system for the spine: a multi-center study of a novel non-fusion system.
        Eur. Spine J. 2002; 11: S170-S178
        • Sutton M.A.
        • McNeill S.R.
        • Helm J.D.
        • Chao Y.J.
        Photomechanics Advances in Two-Dimensional and Three-Dimensional Computer Vision.
        in: Rastogi P.K. Photomechanics. Topics in Applied Physics. 77. Springer-Verlag Berlin, Heidelberg2000: 323-372
        • Tsai K.J.
        • Murakami H.
        • Lowery G.L.
        • Hutton W.C.
        A biomechanical evaluation of an interspinous device (Coflex) used to stabilize the lumbar spine.
        J. Surg. Orthop. Adv. 2006; 15: 167-172
        • Urban J.P.
        • McMullin J.F.
        Swelling pressure of the lumbar intervertebral discs: influence of age, spinal level, composition, and degeneration.
        Spine. 1988; 13: 179-187
        • Wilke H.J.
        • Claes L.
        • Schmitt H.
        • Wolf S.
        A universal spine tester for in vitro experiments with muscle force simulation.
        Eur. Spine J. 1994; 3: 91-97
        • Wilke H.J.
        • Wenger K.
        • Claes L.
        Testing criteria for spinal implants: recommendations for the standardization of in vitro stability testing of spinal implants.
        Eur. Spine J. 1998; 7: 148-154
        • Wilke H.J.
        • Rohlmann F.
        • Neidlinger-Wilke C.
        • Werner K.
        • Claes L.
        • Kettler A.
        Validity and interobserver agreement of a new radiographic grading system for intervertebral disc degeneration: Part I. Lumbar spine.
        Eur. Spine J. 2006; 15: 720-730
        • Wilke H.J.
        • Schmidt H.
        • Werner K.
        • Schmolz W.
        • Drumm J.
        Biomechanical evaluation of a new total posterior-element replacement system.
        Spine. 2006; 31 (discussion 2797): 2790-2796