title: Relevance of using a compressive preload in the cervical spine: an experimental and numerical simulating investigation.
abstract: Simulating compressive action of muscles, a follower load attends to reproduce a more physiological biomechanical behaviour of the cervical spine. Only few experimental studies reported its influence on kinematics and intradiscal pressure in the cervical spine.
  
  
  METHODS
  In vitro human cadaveric and numerical simulating evaluation of a compressive preload in the cervical spine.
  
  
  OBJECTIVE
  To analyse the influence of a compressive follower preload on the biomechanical behaviour of the cervical spine.
  
  
  METHODS
  The present study was divided into two parts: part 1: in vitro investigation; part 2: numerical simulating analysis. Part 1: Twelve human cadaveric spines from C2 to T2 were evaluated intact and after application of a 50-N follower load. All tests were performed under load control by applying pure moments loading of 2 Nm in flexion/extension (FE), axial rotation (AR) and lateral bending (LB). Three-dimensional displacements were measured using an optoelectronic system, and intradiscal pressures were measured at two levels. Part 2: Using a 3D finite element model, we evaluated the influence of a 50- and 100-N compressive preload on intradiscal loads, facets forces and ranges of motion. Different positions of the follower load along the anteroposterior axis (±5 mm) were also simulated.
  
  
  RESULTS
  Part 1: Mean variation of cervical lordosis was 5° ± 3°. The ROM slightly increased in FE, whereas it consistently decreased in AR and LB. Coupled lateral bending during AR was also reduced. Increase in hysteresis was observed on load-displacement curves only for AR and LB. Intradiscal pressures increased, but the aspect of load-pressure curves was altered in AR and LB. Part 2: Using the FE model, only minimal changes in ROM were noted following the simulation of a 50-N compressive load for the three loading conditions. Compared to intact condition, <10% variation was observed with regard to the different magnitude and positioning simulated. Intradiscal loads and facets forces were systematically increased by applying compressive preload.
  
  
  CONCLUSIONS
  Although the follower load represents an attractive option to apply compressive preload during experimental tests, we found that this method could affect the native biomechanical behaviour of spine specimen depending on which movement was considered. Only minimal effects were observed in FE, whereas significant changes in kinematics and intradiscal pressures were observed for AR and LB.
authors.affiliation: University Claude Bernard Lyon 1, Lyon, France, c.barrey@wanadoo.fr.
authors.forename: Cédric
authors.initials: C
authors.lastname: Barrey
authors.forename: Marc-Antoine
authors.initials: MA
authors.lastname: Rousseau
authors.forename: Sylvain
authors.initials: S
authors.lastname: Persohn
authors.forename: Sophie
authors.initials: S
authors.lastname: Campana
authors.forename: Gilles
authors.initials: G
authors.lastname: Perrin
authors.forename: Wafa
authors.initials: W
authors.lastname: Skalli
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D002102:Cadaver; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000502:physiology*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D011312:Pressure; D011859:Radiography; D016059:Range of Motion, Articular; D012399:Rotation; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology*
references.citation: Eur Spine J. 1993 Jun;2(1):2-11
references.pmid: 20058441
references.citation: J Biomech. 1997 Sep;30(9):921-31
references.pmid: 9302615
references.citation: J Orthop Res. 2003 May;21(3):547-52
references.pmid: 12706030
references.citation: Clin Biomech (Bristol, Avon). 1998 Jan;13(1):11-17
references.pmid: 11415766
references.citation: Spine (Phila Pa 1976). 2000 Jun 15;25(12):1548-54
references.pmid: 10851105
references.citation: Eur Spine J. 1998;7(2):148-54
references.pmid: 9629939
references.citation: Spine (Phila Pa 1976). 2001 Dec 15;26(24):E557-61
references.pmid: 11740371
references.citation: Eur Spine J. 2012 Mar;21(3):432-42
references.pmid: 21833571
references.citation: J Biomech. 2009 Jul 22;42(10 ):1409-15
references.pmid: 19442980
references.citation: Spine (Phila Pa 1976). 2002 Jan 1;27(1):43-8
references.pmid: 11805634
references.citation: J Orthop Res. 2003 May;21(3):540-6
references.pmid: 12706029
references.citation: J Neurosurg Spine. 2009 Nov;11(5):538-46
references.pmid: 19929355
references.citation: J Biomech. 2009 Jul 22;42(10):1520-6
references.pmid: 19433325
references.citation: Spine (Phila Pa 1976). 1999 May 15;24(10):1003-9
references.pmid: 10332793
references.citation: Spine (Phila Pa 1976). 2001 Dec 15;26(24):2692-700
references.pmid: 11740357
references.citation: J Biomech. 2007;40(6):1326-32
references.pmid: 16843473
references.citation: J Korean Neurosurg Soc. 2009 Aug;46(2):144-51
references.pmid: 19763217
references.citation: Spine (Phila Pa 1976). 1992 May;17 (5):467-74
references.pmid: 1621143
references.citation: Clin Biomech (Bristol, Avon). 2000 Nov;15(9):633-48
references.pmid: 10946096
references.citation: J Orthop Res. 1991 Nov;9(6):828-34
references.pmid: 1919845
references.citation: Clin Biomech (Bristol, Avon). 1991 May;6(2):111-7
references.pmid: 23915484
references.citation: Spine (Phila Pa 1976). 2008 Jan 1;33(1):E10-4
references.pmid: 18165735
references.citation: J Bone Joint Surg Am. 2006 Apr;88 Suppl 2:103-9
references.pmid: 16595454
references.citation: Bull Acad Natl Med. 2005 Feb;189(2):287-97; discussion 297-300
references.pmid: 16114859
references.citation: Spine (Phila Pa 1976). 1995 Nov 1;20(21):2354-7
references.pmid: 8553127
references.citation: Spine (Phila Pa 1976). 2004 Dec 15;29(24):2809-14
references.pmid: 15599283
references.citation: Spine (Phila Pa 1976). 2003 Oct 15;28(20):S176-85
references.pmid: 14560189
references.citation: J Bone Joint Surg Am. 2003 Sep;85-A(9):1749-56
references.pmid: 12954834
references.citation: Orthop Clin North Am. 1977 Jan;8(1):181-92
references.pmid: 857225
references.citation: Neurosurgery. 1999 Feb;44(2):379-84; discussion 384-5
references.pmid: 9932892
references.citation: Spine (Phila Pa 1976). 2007 Nov 1;32(23 ):2569-72
references.pmid: 17978655