Back to Search
Start Over
In vitro axial preload application during spine flexibility testing: towards reduced apparatus-related artefacts
- Source :
- Journal of Biomechanics. 33:1559-1568
- Publication Year :
- 2000
- Publisher :
- Elsevier BV, 2000.
-
Abstract
- Presently, there is little consensus about how, or even if, axial preload should be incorporated in spine flexibility tests in order to simulate the compressive loads naturally present in vivo. Some preload application methods are suspected of producing unwanted “artefact” forces as the specimen rotates and, in doing so, influencing the resulting kinematics. The objective of this study was to quantitatively compare four distinct types of preload which have roots in contemporary experimental practice. The specific quantities compared were the reaction moments and forces resulting at the intervertebral disc and specimen kinematics. The preload types incorporated increasing amounts of caudal constraint on the preload application vector ranging from an unconstrained dead-load arrangement to an apparatus that allowed the vector to follow rotations of the specimen. Six human cadaveric spine segments were tested (1-L1/L2, 3-L2/L3, 1-L3/L4 and 1-L4/L5). Pure moments were applied to the specimens with each of the four different types of compressive preload. Kinematic response was measured using an opto-electronic motion analysis system. A six-axis load cell was used to measure reaction forces and moments. Artefact reaction moments and shear forces were significantly affected by preload application method and magnitude. Unconstrained preload methods produced high artefact moments and low artefact shear forces while more constrained methods did the opposite. A mechanical trade-off is suggested by our results, whereby unwanted moment can only be prevented at the cost of shear force production. When comparing spine flexibility studies, caution should be exercised to ensure preload was applied in a similar manner for all studies. Unwanted moments or forces induced as a result of preload application method may render the comparison of two seemingly similar studies inappropriate.
- Subjects :
- Motion analysis
Materials science
Flexibility (anatomy)
Rotation
Shear force
Biomedical Engineering
Biophysics
Kinematics
Load cell
Weight-Bearing
Cadaver
medicine
Humans
Orthopedics and Sports Medicine
Range of Motion, Articular
Intervertebral Disc
Pliability
business.industry
Rehabilitation
Biomechanics
Structural engineering
musculoskeletal system
Spine
Biomechanical Phenomena
Preload
medicine.anatomical_structure
Moment (physics)
Artifacts
business
Subjects
Details
- ISSN :
- 00219290
- Volume :
- 33
- Database :
- OpenAIRE
- Journal :
- Journal of Biomechanics
- Accession number :
- edsair.doi.dedup.....8c1ab910e00da83baca648cbce7ada16