title: A new dynamic six degrees of freedom disc-loading simulator allows to provoke disc damage and herniation.
abstract: The cause of disc herniation is not well understood yet. It is assumed that heavy lifting and extreme postures can cause small injuries starting either in the inner anulus or from the outside close to the endplate. Such injuries are accumulated over years until its structure is weakened and finally a single loading event leads to a sudden failure of the last few intact lamellae. This paper describes a novel, custom-developed dynamic 6-DOF disc-loading simulator that allows complex loading to provoke such disc damage and herniations.
  
  
  
  The machine's axes are driven by six independent servomotors providing high loads (10 kN axial compression, 2 kN shear, 100 Nm torque) up to 5 Hz. A positional accuracy test was conducted to validate the machine. Subsequently, initial experiments with lumbar ovine motion segments under complex loading were performed. After testing, the discs were examined in an ultra-high field MRI (11.7 T). A three-dimensional reconstruction was performed to visualise the internal disc lesions.
  
  
  
  Validation tests demonstrated positioning with an accuracy of ≤0.08°/≤0.026 mm at 0.5 Hz and ≤0.27°/≤0.048 mm at 3.0 Hz with amplitudes of ±17°/±2 mm. Typical failure patterns and herniations could be provoked with complex asymmetrical loading protocols. Loading with axial compression, flexion, lateral bending and torsion lead in 8 specimens to 4 herniated discs, two protrusions and two delaminations. All disc failures occurred in the posterior region of the disc.
  
  
  
  This new dynamic disc-loading simulator has proven to be able to apply complex motion combinations and allows to create artificial lesions in the disc with complex loading protocols. The aim of further tests is to better understand the mechanisms by which disc failure occurs at the microstructural level under different loading conditions. Visualisation with ultra-high field MRI at different time points is a promising method to investigate the gradual development of such lesions, which may finally lead to disc failure. These kinds of experiments will help to better investigate the mechanical failure of discs to provide new insights into the initiation of intervertebral disc herniation. This device will also serve for many other applications in spine biomechanics research.
authors.affiliation: Institute of Orthopedic Research and Biomechanics, Center of Musculoskeletal Research (zmfu), Helmholtzstraße 14, 89081, Ulm, Germany. hans-joachim.wilke@uni-ulm.de.
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Wilke
authors.affiliation: SpineServ GmbH and Co. KG, Söflinger Straße 100, 89077, Ulm, Germany.
authors.forename: Annette
authors.initials: A
authors.lastname: Kienle
authors.affiliation: Institute of Orthopedic Research and Biomechanics, Center of Musculoskeletal Research (zmfu), Helmholtzstraße 14, 89081, Ulm, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Maile
authors.affiliation: Department of Internal Medicine II, University Hospital Ulm, Albert-Einstein-Allee 23, 89081, Ulm, Germany.|Small Animal MRI, Medical Faculty, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Rasche
authors.affiliation: Institute of Orthopedic Research and Biomechanics, Center of Musculoskeletal Research (zmfu), Helmholtzstraße 14, 89081, Ulm, Germany.
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Berger-Roscher
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D035843:Biomedical Research / Q000295:instrumentation* / Q000379:methods; D004195:Disease Models, Animal; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000502:physiology / Q000601:surgery; D007405:Intervertebral Disc Displacement / Q000000981:diagnostic imaging / Q000601:surgery; D012756:Sheep
keywords: 6-DOF; Complex loading; Disc-loading simulator; Dynamic spine tester; Endplate junction failure; Herniation; Intervertebral disc
references.citation: Spine (Phila Pa 1976). 2010 Oct 1;35(21):1897-908
references.pmid: 20838275
references.citation: Eur Spine J. 2010 Dec;19(12):2171-80
references.pmid: 20683625
references.citation: Spine (Phila Pa 1976). 1980 May-Jun;5(3):245-53
references.pmid: 7394664
references.citation: Eur Spine J. 2011 Nov;20(11):1859-68
references.pmid: 21674213
references.citation: Spine (Phila Pa 1976). 2008 Dec 1;33(25):2728-40
references.pmid: 19050578
references.citation: Surg Forum. 1958;9:690-5
references.pmid: 13635481
references.citation: Bone. 2006 Aug;39(2):336-44
references.pmid: 16580272
references.citation: J Biomech. 2002 Apr;35(4):517-21
references.pmid: 11934421
references.citation: Clin Biomech (Bristol, Avon). 2005 Dec;20(10):1038-45
references.pmid: 16098646
references.citation: J Bone Joint Surg Am. 1970 Apr;52(3):468-97
references.pmid: 5425641
references.citation: Eur Spine J. 1994;3(2):91-7
references.pmid: 7874556
references.citation: Spine (Phila Pa 1976). 2013 Aug 1;38(17):1491-500
references.pmid: 23680832
references.citation: Spine (Phila Pa 1976). 2007 Apr 1;32(7):748-55
references.pmid: 17414908
references.citation: J Biomech Eng. 2002 Aug;124(4):471-7
references.pmid: 12188214
references.citation: Eur Spine J. 1998;7(2):148-54
references.pmid: 9629939
references.citation: Spine (Phila Pa 1976). 1997 Oct 15;22(20):2365-74
references.pmid: 9355217
references.citation: Osteoarthritis Cartilage. 2015 Jul;23(7):1057-70
references.pmid: 25827971
references.citation: J Bone Joint Surg Am. 1955 Dec;37-A(6):1188-96
references.pmid: 13271464
references.citation: J Spinal Disord. 1988;1(1):16-32
references.pmid: 2980059
references.citation: J Biomech. 1981;14(7):447-60
references.pmid: 7276006
references.citation: Eur Spine J. 2015 Nov;24(11):2488-95
references.pmid: 26206293
references.citation: Spine J. 2014 Jul 1;14(7):1308-17
references.pmid: 24321131
references.citation: J Bone Joint Surg Am. 1978 Jan;60(1):41-55
references.pmid: 624758
references.citation: J Orthop Res. 1996 May;14(3):500-3
references.pmid: 8676264
references.citation: PLoS One. 2013 Jul 24;8(7):e69610
references.pmid: 23894509
references.citation: Clin Biomech (Bristol, Avon). 2007 Mar;22(3):257-65
references.pmid: 17196720
references.citation: Int Orthop. 1982;6(4):249-53
references.pmid: 7183577
references.citation: Spine J. 2014 Feb 1;14(2):300-7
references.pmid: 24231779
references.citation: Spine (Phila Pa 1976). 1982 May-Jun;7(3):184-91
references.pmid: 7112236
references.citation: Clin Biomech (Bristol, Avon). 2014 Feb;29(2):155-60
references.pmid: 24345591
references.citation: J Bone Joint Surg Am. 1957 Oct;39-A(5):1135-64
references.pmid: 13475413
references.citation: Spine (Phila Pa 1976). 1983 Nov-Dec;8(8):857-65
references.pmid: 6230741
references.citation: J Bone Joint Surg Br. 1983 Mar;65(2):199-203
references.pmid: 6826631
references.citation: Spine (Phila Pa 1976). 1995 Oct 1;20(19):2097-100
references.pmid: 8588165
references.citation: J Orthop Res. 2010 Jun;28(6):773-7
references.pmid: 20058270
references.citation: Eur Spine J. 2014 Jan;23(1):19-26
references.pmid: 24121748
references.citation: J Bone Joint Surg Br. 1951 Nov;33-B(4):607-11
references.pmid: 14880588
references.citation: Clin Biomech (Bristol, Avon). 2010 Jan;25(1):6-9
references.pmid: 19815318
references.citation: Clin Biomech (Bristol, Avon). 2001 Jan;16(1):28-37
references.pmid: 11114441
references.citation: J Biomech. 2014 Sep 22;47(12):3241-7
references.pmid: 25016485
references.citation: J Biomech. 2013 Jul 26;46(11):1948-54
references.pmid: 23764173
references.citation: Spine (Phila Pa 1976). 1985 Dec;10(10):894-900
references.pmid: 3832457
references.citation: J Biomech Eng. 1993 Aug;115(3):211-7
references.pmid: 8231133
references.citation: Spine (Phila Pa 1976). 1985 Jul-Aug;10(6):524-31
references.pmid: 4081867
references.citation: Spine (Phila Pa 1976). 2014 Jun 1;39(13):1018-28
references.pmid: 24503692
references.citation: Spine (Phila Pa 1976). 1981 May-Jun;6(3):241-8
references.pmid: 7268544
references.citation: Bone. 2003 Oct;33(4):540-8
references.pmid: 14555257