Spine Structure Mechanics

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Spine Structure Mechanics

• J. Marcus Hollis
• Sudhakar G. Madanagopal, M.D.
• A.E. Engin, Ph.D.
• Sreenivasulu Kolakanuru,M.S.
• University of South Alabama

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Thanks toSCIB Funding

• Initiate robotic Spine testing
• Train graduate students that are now full time
  staff with industrial support
• Additional Industrial Support for Robotic Spine
  testing in the Biomechanics Lab

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Objective

• Develop Method for Determining Spine motion
  segment and substructure mechanical properties
  efficiently
• Maximum amount of data per specimen

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Winkelstein MyersJournal of Biomechanical
Engineering OCTOBER 2002, Vol. 124 511
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6 D.O.F. Testing Robot
Essential a 6 D.O.F. Actuator Allows for
simultaneous control of motion in all three
translations and three rotations. When used with
a 6 D.O.F, load cell and appropriate software
allows for control of all six loading components
on a structure or a combination of Force Control
D.O.F.s and Position Control D.O.F.s
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Original Robot Tester Development - Knees

• J Biomech. 1996 Forces and moments in six-DOF at
  the human knee joint mathematical description
  for control.?Fujie H, Livesay GA, Fujita M, Woo
  SL.Department of Biomedical Engineering, School
  of Medicine, Kitasato University, Kanagawa,
  Japan.
• J Biomech Eng. 1995 A six-degree-of-freedom test
  system for the study of joint mechanics and
  ligament forces.?Hollis JM.Orthopaedic
  Biomechanics Laboratory. University of Arkansas
  for Medical Sciences, Little Rock, 72205, USA.

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A robot is an electro-mechanical or
bio-mechanical device or group of devices that
can perform autonomous or preprogrammed tasks.

• Wikipedia

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Adapt a Six Degree of Freedom Robotic Testing
Machine for Spine Testing
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Testing of cervical spine
Experimental procedure
Specimen was fixed in the cups. Whole setup was
fixed in the machine with zero load on the
specimen.
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Results
Joint capsule
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Testing of cervical spine
Experimental procedure

• Insertion sites position data was recorded once
  the bodies were separated.

Insertion sites position
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Testing of cervical spine
Ligament force calculation
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Testing of cervical spine
Ligament length calculation
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Results
Anterior Longitudinal ligament
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Results
Anterior Longitudinal ligament
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Results
Anterior Longitudinal ligament
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Results
Intervertebral disc
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Results
Intervertebral disc
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Results
Intervertebral disc
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Results
Joint capsule
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Results
Joint capsule
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Significance

• This investigation will establish newer testing
  methodology, which will enable faster and more
  resource efficient biomechanical testing of the
  spine.

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Data generated from a test on one specimen

• Multi directional load-displacement data for the
  motion segment.
• Contribution of soft tissue sub structures to
  motion segment stiffness in multiple loadings.
• The load in a soft tissue structure for an
  applied external motion segment load.
• Force-displacement information for individual
  soft tissue structures.
• Attachment site geometry.
• Soft tissue simple strain under a variety of
  loads.
• Stress-strain behavior for some structures
• Non-linear bending stiffness of the disk in
  simple and combined loadings.

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Limitations

• Slow loading rate
• Load distribution result applicable to impact
  loading is dependent on similar reduced
  relaxation function among soft tissue structures.
• Difficulty in isolating and removing some soft
  tissue structures.
• Wrapping of soft tissue around bone that is not
  accounted for in length calculations.
• A more sophisticated geometric model would be
  helpful for some tissues
• Limited upper range of applied loads to reduce
  chance of fixation and specimen failure.
• A concern with older tissue donors

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Thanks SCIB
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Future

• Test more specimens
• Look for more collaborators