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Biomechanical characterization of the three-dimensional kinematic behaviour of the Dynesys dynamic stabilization system: an in vitro study

European Spine Journal volume 15, pages 913–922 (2006)Cite this article

Abstract

The Dynesys, a flexible posterior stabilization system that provides an alternative to fusion, is designed to preserve intersegmental kinematics and alleviate loading at the facet joints. Recent biomechanical evidence suggests that the overall range of motion (ROM) with the Dynesys is less than the intact spine. The purpose of this investigation was to conduct a comprehensive characterization of the three-dimensional kinematic behaviour of the Dynesys and determine if the length of the Dynesys polymer spacer contributes to differences in the kinematic behaviour at the implanted level. Ten cadaveric lumbar spine segments (L2–L5) were tested by applying a pure moment of ±7.5 Nm in flexion–extension, lateral bending, and axial rotation, with and without a follower preload of 600 N. Test conditions included: (a) intact; (b) injury; (c) injury stabilized with Dynesys at L3–L4 (standard spacer); (d) long spacer (+2 mm); and (e) short spacer (−2 mm). Intervertebral rotations were measured using an optoelectronic camera system. The intersegmental range of motion (ROM), neutral zone (NZ), and three-dimensional helical axis of motion (HAM) were calculated. Statistical significance of changes in ROM, NZ, and HAM was determined using repeated measures analysis of variance (ANOVA) and Student–Newman–Keuls post-hoc analysis with P<0.05. Implantation of the standard length Dynesys significantly reduced ROM compared to the intact and injured specimens, with the least significant changes seen in axial rotation. Injury typically increased the NZ, but implantation of the Dynesys restored the NZ to a magnitude less that that of the intact spine. The Dynesys produced a significant posterior shift in the HAM in flexion–extension and axial rotation. The spacer length had a significant effect on ROM with the long spacer resulting in the largest ROM in all loading directions without a follower preload. The largest differences were in axial rotation. A 4 mm increase in spacer length led to an average intersegmental motion increase of 30% in axial rotation, 23% in extension, 14% in flexion, and 11% in lateral bending. There were no significant changes in NZ with different spacer lengths. Typically, the short spacer caused a greater shift and a greater change in orientation of the HAM than the long spacer. The long spacer resulted in a ROM and a motion pattern, as represented by the HAM, that was closer to that seen in an intact specimen. The results of this study suggest that the length of the Dynesys spacer altered the segmental position and therefore affected kinematic behaviour.

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References

  1. Andersson GB (1999) Epidemiological features of chronic low-back pain. Lancet 354:581–585

    Article  PubMed  Google Scholar 

  2. Eck JC, Humphreys SC, Hodges SD (1999) Adjacent-segment degeneration after lumbar fusion: a review of clinical, biomechanical, and radiologic studies. Am J Orthop 28:336–340

    PubMed  Google Scholar 

  3. Freudiger S, Dubois G, Lorrain M (1999) Dynamic neutralisation of the lumbar spine confirmed on a new lumbar spine simulator in vitro. Arch Orthop Trauma Surg 119:127–132

    Article  PubMed  Google Scholar 

  4. Fritzell P, Hagg O, Wessberg P, et al (2001) Volvo award winner in clinical studies: lumbar fusion versus nonsurgical treatment for chronic low back pain: a multicenter randomized controlled trial from the Swedish Lumbar Spine Study Group. Spine 26:2521–2532 (discussion 32–34)

    Article  PubMed  Google Scholar 

  5. Fujiwara A, Lim TH, An HS, et al (2000) The effect of disc degeneration and facet joint osteoarthritis on the segmental flexibility of the lumbar spine. Spine 25:3036–3044

    Article  PubMed  Google Scholar 

  6. Gardner-Morse MG, Stokes IA (2003) Physiological axial compressive preloads increase motion segment stiffness, linearity and hysteresis in all six degrees of freedom for small displacements about the neutral posture. J Orthop Res 21:547–552

    Article  PubMed  Google Scholar 

  7. Goertzen DJ, Lane C, Oxland TR (2004) Neutral zone and range of motion in the spine are greater with stepwise loading than with a continuous loading protocol. An in vitro porcine investigation. J Biomech 37:257–261

    Article  PubMed  Google Scholar 

  8. Kinzel GL, Hall AS Jr, Hillberry BM (1972) Measurement of the total motion between two body segments. I. Analytical development. J Biomech 5:93–105

    Article  PubMed  Google Scholar 

  9. Lee CK (1988) Accelerated degeneration of the segment adjacent to a lumbar fusion. Spine 13:375–377

    PubMed  Google Scholar 

  10. Lund T, Rathonyi G, Schlenzka D, et al (1999) The external spinal fixator does not reduce anterior column motion under axial compressive loads. A mechanical in vitro study. Acta Orthop Scand 70:37–41

    PubMed  Google Scholar 

  11. McKinnon ME, Vickers MR, Ruddock VM, et al (1997) Community studies of the health service implications of low back pain. Spine 22:2161–2166

    Article  PubMed  Google Scholar 

  12. Mimura M, Panjabi MM, Oxland TR, et al (1994) Disc degeneration affects the multidirectional flexibility of the lumbar spine. Spine 19:1371–1380

    PubMed  Google Scholar 

  13. Niosi CA, Zhu QA, Wilson DC, et al (2004) Does spacer length of dynamic posterior stablization system have an effect on range of motion? ISSLS 31st Annual Meeting (Poster) Porto, Portugal

  14. Panjabi MM, Krag MH, Goel VK (1981) A technique for measurement and description of three-dimensional six degree-of-freedom motion of a body joint with an application to the human spine. J Biomech 14:447–460

    Article  PubMed  Google Scholar 

  15. Panjabi MM, Oxland TR, Yamamoto I, et al (1994) Mechanical behavior of the human lumbar and lumbosacral spine as shown by three-dimensional load–displacement curves. J Bone Joint Surg Am 76:413–424

    PubMed  Google Scholar 

  16. Patwardhan AG, Havey RM, Meade KP, et al (1999) A follower load increases the load-carrying capacity of the lumbar spine in compression. Spine 24:1003–1009

    Article  PubMed  Google Scholar 

  17. Patwardhan AG, Havey RM, Carandang G, et al (2003) Effect of compressive follower preload on the flexion–extension response of the human lumbar spine. J Orthop Res 21:540–546

    Article  PubMed  Google Scholar 

  18. Rohlmann A, Neller S, Claes L, et al (2001) Influence of a follower load on intradiscal pressure and intersegmental rotation of the lumbar spine. Spine 26:E557–E561

    Article  PubMed  Google Scholar 

  19. Schlegel JD, Smith JA, Schleusener RL (1996) Lumbar motion segment pathology adjacent to thoracolumbar, lumbar, and lumbosacral fusions. Spine 21:970–981

    Article  PubMed  Google Scholar 

  20. Schmoelz W, Huber JF, Nydegger T, et al (2003) Dynamic stabilization of the lumbar spine and its effects on adjacent segments: an in vitro experiment. J Spinal Disord Tech 16:418–23

    PubMed  Google Scholar 

  21. Stoll TM, Dubois G, Schwarzenbach O (2002) The dynamic neutralization system for the spine: a multi-center study of a novel non-fusion system. Eur Spine J 11(Suppl 2):S170–S178

    PubMed  Google Scholar 

  22. Woltring HJ, Huiskes R, de Lange A, et al (1985) Finite centroid and helical axis estimation from noisy landmark measurements in the study of human joint kinematics. J Biomech 18:379–389

    Article  PubMed  Google Scholar 

  23. Yamamoto I, Panjabi MM, Crisco T, et al (1989) Three-dimensional movements of the whole lumbar spine and lumbosacral joint. Spine 14:1256–1260

    PubMed  Google Scholar 

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Acknowledgements

The authors wish to gratefully acknowledge the funding from the Synos Foundation, Switzerland, Zimmer GmbH, and Natural Sciences and Engineering Research Council of Canada (NSERC). The experiments in this study complied with the current testing laws in Canada and were approved by the University of British Columbia Clinical Research Ethics Board.

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  1. Division of Orthopaedic Engineering Research, Departments of Mechanical Engineering and Orthopaedics, University of British Columbia and Vancouver Coastal Health Research Institute, 828 W 10th Avenue, 5th floor, V5Z 1L8, Vancouver, BC, Canada

    Christina A. Niosi, Qingan A. Zhu, Derek C. Wilson, Ory Keynan, David R. Wilson & Thomas R. Oxland

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  1. Christina A. Niosi
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  2. Qingan A. Zhu
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  3. Derek C. Wilson
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  4. Ory Keynan
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  5. David R. Wilson
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  6. Thomas R. Oxland
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Correspondence to Thomas R. Oxland.

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Niosi, C.A., Zhu, Q.A., Wilson, D.C. et al. Biomechanical characterization of the three-dimensional kinematic behaviour of the Dynesys dynamic stabilization system: an in vitro study. Eur Spine J 15, 913–922 (2006). https://doi.org/10.1007/s00586-005-0948-9

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  • DOI: https://doi.org/10.1007/s00586-005-0948-9

Keywords

  • Biomechanics
  • Lumbar spine
  • Non-fusion
  • Stabilization
  • Surgical treatment