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Biomechanical evaluation of a posterior non-fusion instrumentation of the lumbar spine

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Numerous posterior non-fusion systems have been developed within the past decade to resolve the disadvantages of rigid instrumentations and preserve spinal motion. The aim of this study was to investigate the effect of a new dynamic stabilization device, to measure the screw anchorage after flexibility testing and compare it with data reported in the literature.


Six human lumbar spine motion segments (L2–5) were loaded in a spine tester with pure moments of 7.5 Nm in lateral bending, flexion/extension and axial rotation. Specimens were tested intact, after instrumentation of the intact segment, after destabilization by a nucleotomy and after instrumentation of the destabilised segment with the new non-fusion device (Elaspine). After flexibility testing all screws were subjected to a pull-out test.


Instrumentation of the intact segment significantly reduced the RoM (p < 0.002) in flexion, extension and lateral bending to 49.7, 44.6 and 53% of the intact state, respectively. In axial rotation, the instrumentation resulted in a non-significant RoM reduction to 95% of the intact state. Compared to the intact segment, instrumentation of the destabilized segment significantly (p < 0.05) reduced the RoM to 69.8, 62.3 and 79.1% in flexion, extension and lateral bending, respectively. In axial rotation, the instrumented segment showed a significantly higher RoM than the intact segment (137.6% of the intact state (p < 0.01)). The pull-out test showed a maximum pull-out force of 855.1 N (±334) with a displacement of 6.1 mm (±2.8) at maximum pull-out force.


The effect of the investigated motion preservation device on the RoM of treated segments is in the range of other devices reported in the literature. Compared to the most implanted and investigated device, the Dynesys, the Elaspine has a less pronounced motion restricting effect in lateral bending and flexion/extension, while being less effective in limiting axial rotation. The pull-out force of the pedicle screws demonstrated anchorage comparable to other screw designs reported in the literature.

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  1. Andersson GB (1999) Epidemiological features of chronic low-back pain. Lancet 354(9178):581–585

    Article  PubMed  CAS  Google Scholar 

  2. Fritzell P, Hagg O, Wessberg P, Nordwall A (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 (Phila Pa 1976) 26 (23):2521–2532; discussion 2532–2524

  3. Gibson JN, Waddell G (2005) Surgery for degenerative lumbar spondylosis: updated Cochrane Review. Spine (Phila Pa 1976) 30 (20):2312–2320

    Google Scholar 

  4. Disch AC, Schmoelz W, Matziolis G, Schneider SV, Knop C, Putzier M (2008) Higher risk of adjacent segment degeneration after floating fusions: long-term outcome after low lumbar spine fusions. J Spinal Disord Tech 21(2):79–85

    Article  PubMed  Google Scholar 

  5. Hilibrand AS, Robbins M (2004) Adjacent segment degeneration and adjacent segment disease: the consequences of spinal fusion? Spine J 4(6 Suppl):190S–194S

    Article  PubMed  Google Scholar 

  6. Khoueir P, Kim KA, Wang MY (2007) Classification of posterior dynamic stabilization devices. Neurosurg Focus 22(1):E3

    Article  PubMed  Google Scholar 

  7. Gedet P, Haschtmann D, Thistlethwaite PA, Ferguson SJ (2009) Comparative biomechanical investigation of a modular dynamic lumbar stabilization system and the Dynesys system. Eur Spine J 18(10):1504–1511

    Article  PubMed  Google Scholar 

  8. Schmoelz W, Huber JF, Nydegger T, Dipl I, Claes L, Wilke HJ (2003) Dynamic stabilization of the lumbar spine and its effects on adjacent segments: an in vitro experiment. J Spinal Disord Tech 16(4):418–423

    Article  PubMed  CAS  Google Scholar 

  9. Knop C, Lange U, Bastian L, Blauth M (2000) Three-dimensional motion analysis with Synex. Comparative biomechanical test series with a new vertebral body replacement for the thoracolumbar spine. Eur Spine J 9(6):472–485

    Article  PubMed  CAS  Google Scholar 

  10. Panjabi MM (1988) Biomechanical evaluation of spinal fixation devices: I. A conceptual framework. Spine 13(10):1129–1134

    Article  PubMed  CAS  Google Scholar 

  11. Wilke HJ, Wenger K, Claes L (1998) Testing criteria for spinal implants: recommendations for the standardization of in vitro stability testing of spinal implants. Eur Spine J 7(2):148–154

    Article  PubMed  CAS  Google Scholar 

  12. Wilke HJ, Heuer F, Schmidt H (2009) Prospective design delineation and subsequent in vitro evaluation of a new posterior dynamic stabilization system. Spine (Phila Pa 1976) 34 (3):255–261

    Google Scholar 

  13. Schmoelz W, Onder U, Martin A, von Strempel A (2009) Non-fusion instrumentation of the lumbar spine with a hinged pedicle screw rod system: an in vitro experiment. Eur Spine J 18(10):1478–1485

    Article  PubMed  Google Scholar 

  14. Schilling C, Kruger S, Grupp TM, Duda GN, Blomer W, Rohlmann A (2010) The effect of design parameters of dynamic pedicle screw systems on kinematics and load bearing: an in vitro study. Eur Spine J 20:297–307

    Article  PubMed  Google Scholar 

  15. Bozkus H, Senoglu M, Baek S, Sawa AG, Ozer AF, Sonntag VK, Crawford NR (2010) Dynamic lumbar pedicle screw-rod stabilization: in vitro biomechanical comparison with standard rigid pedicle screw-rod stabilization. J Neurosurg Spine 12(2):183–189

    Article  PubMed  Google Scholar 

  16. Niosi CA, Zhu QA, Wilson DC, Keynan O, Wilson DR, Oxland TR (2006) Biomechanical characterization of the three-dimensional kinematic behaviour of the Dynesys dynamic stabilization system: an in vitro study. Eur Spine J 15(6):913–922

    Article  PubMed  Google Scholar 

  17. Panjabi MM, Henderson G, James Y, Timm JP (2007) StabilimaxNZ) versus simulated fusion: evaluation of adjacent-level effects. Eur Spine J 16(12):2159–2165

    Article  PubMed  Google Scholar 

  18. Schulte TL, Hurschler C, Haversath M, Liljenqvist U, Bullmann V, Filler TJ, Osada N, Fallenberg EM, Hackenberg L (2008) The effect of dynamic, semi-rigid implants on the range of motion of lumbar motion segments after decompression. Eur Spine J 17(8):1057–1065

    Article  PubMed  Google Scholar 

  19. Cunningham BW, Dawson JM, Hu N, Kim SW, McAfee PC, Griffith SL (2010) Preclinical evaluation of the Dynesys posterior spinal stabilization system: a nonhuman primate model. Spine J 10(9):775–783

    Article  PubMed  Google Scholar 

  20. Ko CC, Tsai HW, Huang WC, Wu JC, Chen YC, Shih YH, Chen HC, Wu CL, Cheng H (2010) Screw loosening in the Dynesys stabilization system: radiographic evidence and effect on outcomes. Neurosurg Focus 28(6):E10

    Article  PubMed  Google Scholar 

  21. Ianuzzi A, Kurtz SM, Kane W, Shah P, Siskey R, van Ooij A, Bindal R, Ross R, Lanman T, Buttner-Janz K, Isaza J (2010) In vivo deformation, surface damage, and biostability of retrieved Dynesys systems. Spine (Phila Pa 1976) 35 (23):E1310–E1316

  22. Liu CL, Zhong ZC, Shih SL, Hung C, Lee YE, Chen CS (2010) Influence of Dynesys system screw profile on adjacent segment and screw. J Spinal Disord Tech 23(6):410–417

    Article  PubMed  Google Scholar 

  23. Meyers K, Tauber M, Sudin Y, Fleischer S, Arnin U, Girardi F, Wright T (2008) Use of instrumented pedicle screws to evaluate load sharing in posterior dynamic stabilization systems. Spine J 8(6):926–932

    Article  PubMed  Google Scholar 

  24. Bozkus H, Senoglu M, Baek S, Sawa AG, Ozer AF, Sonntag VK, Crawford NR (2010) Dynamic lumbar pedicle screw-rod stabilization: in vitro biomechanical comparison with standard rigid pedicle screw-rod stabilization. J Neurosurg Spine 12 (2):183–189

    Google Scholar 

  25. Scifert JL, Sairyo K, Goel VK, Grobler LJ, Grosland NM, Spratt KF, Chesmel KD (1999) Stability analysis of an enhanced load sharing posterior fixation device and its equivalent conventional device in a calf spine model. Spine (Phila Pa 1976) 24 (21):2206–2213

  26. Bullmann V, Schmoelz W, Richter M, Grathwohl C, Schulte TL (2010) Revision of cannulated and perforated cement-augmented pedicle screws: a biomechanical study in human cadavers. Spine (Phila Pa 1976) 35:E932–E939

    Google Scholar 

  27. Masaki T, Sasao Y, Miura T, Torii Y, Kojima A, Aoki H, Beppu M (2009) An experimental study on initial fixation strength in transpedicular screwing augmented with calcium phosphate cement. Spine (Phila Pa 1976) 34 (20):E724–E728

    Google Scholar 

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The study was supported by institutional funds of Spinelab AG, Winterthur, Switzerland. None of the authors received personal funding.

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Correspondence to Werner Schmoelz.

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Schmoelz, W., Erhart, S., Unger, S. et al. Biomechanical evaluation of a posterior non-fusion instrumentation of the lumbar spine. Eur Spine J 21, 939–945 (2012).

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