Spine stability after implantation of an interspinous device al testing of one- and two-level ProDisc-L versus simulated fusions. Spine 32:1311–1319, 2007 16. Pitzen T, Geisler F, Matthis D, Müller-Storz H, Barbier D, Steudel WI, et al: A finite element model for predicting the biomechanical behaviour of the human lumbar spine. Control Eng Pract 10:83–90, 2002 17. Schmidt H, Heuer F, Claes L, Wilke HJ: The relation between the instantaneous center of rotation and facet joint forces – A finite element analysis. Clin Biomech (Bristol, Avon) 23: 270–278, 2008 18. Schmidt H, Heuer F, Drumm J, Klezl Z, Claes L, Wilke HJ: Application of a calibration method provides more realistic results for a finite element model of a lumbar spinal segment. Clin Biomech (Bristol, Avon) 22:377–384, 2007 19. Stokes IA, Iatridis JC: Mechanical conditions that accelerate intervertebral disc degeneration: overload versus immobilization. Spine 29:2724–2732, 2004 20. Tosteson AN, Lurie JD, Tosteson TD, Skinner JS, Herkowitz H, Albert T, et al: Surgical treatment of spinal stenosis with
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and without degenerative spondylolisthesis: cost-effectiveness after 2 years. Ann Intern Med 149:845–853, 2008 21. Wilke HJ, Claes L, Schmitt H, Wolf S: A universal spine tester for in vitro experiments with muscle force simulation. Eur Spine J 3:91–97, 1994 22. Wilke HJ, Drumm J, Häussler K, Mack C, Steudel WI, Kettler A: Biomechanical effect of different lumbar interspinous implants on flexibility and intradiscal pressure. Eur Spine J 17:1049–1056, 2008 23. Wilke HJ, Wenger K, Claes L: Testing criteria for spinal implants: recommendations for the standardization of in vitro stability testing of spinal implants. Eur Spine J 7:148–154, 1998 Manuscript submitted November 4, 2009. Accepted June 17, 2010. Address correspondence to: Federica Anasetti, M.S.Eng., IRCCS Istituto Ortopedico Galeazzi, via Galeazzi 4, 20161 Milan, Italy. email: federicaanasetti@gmail.com.
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