Document Detail


Flow-related mechanics of the intervertebral disc: the validity of an in vitro model.
MedLine Citation:
PMID:  16166881     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
STUDY DESIGN: An in vitro mechanical study on porcine motion segments. OBJECTIVES: To test the validity of in vitro studies of the flow-related mechanics of the intervertebral disc and, in particular, to investigate whether fluid flows back into the disc during unloading after a loading cycle. SUMMARY OF BACKGROUND DATA: In vivo studies show both the inflow and outflow of fluid in the intervertebral disc. The resistance to flow out of the disc is higher than to inflow. The fluid flow is regulated via unbalance between the external load and the osmotic pressure of the nucleus pulposus. MATERIALS: There were 8 porcine lumbar motion segments (without posterior elements) and 8 isolated discs tested in a physiologic saline bath (39 degrees C). The specimens were preloaded at 0.025 MPa for 15 minutes. Three 15-minute loading periods at 2.0 MPa were applied, each followed by an unloading period of 30 minutes. Loads, axial displacements, and nucleus pressure were recorded online. RESULTS: Over the 3 loading and unloading periods, all specimens showed a net loss of height and mass. The time series of specimen height during the 3 unloading periods showed virtually identical responses. The pressure in the nucleus decreased in the subsequent loading periods and showed no increase during unloading. CONCLUSION: The data show the limitations of an in vitro model for studying fluid flow-related intervertebral disc mechanics. During loading, outflow of fluid occurred, but inflow appears to be virtually absent during unloading. Poro-elastic behavior cannot be reproduced in an in vitro model.
Authors:
Albert J van der Veen; Margriet Mullender; Theo H Smit; Idsart Kingma; Jaap H van Dieën
Publication Detail:
Type:  In Vitro; Journal Article; Validation Studies    
Journal Detail:
Title:  Spine     Volume:  30     ISSN:  1528-1159     ISO Abbreviation:  Spine     Publication Date:  2005 Sep 
Date Detail:
Created Date:  2005-09-16     Completed Date:  2006-03-09     Revised Date:  2009-07-09    
Medline Journal Info:
Nlm Unique ID:  7610646     Medline TA:  Spine (Phila Pa 1976)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  E534-9     Citation Subset:  IM    
Affiliation:
Department of Physics and Medical Technology, VU University Medical Center, Amsterdam, The Netherlands. aj.veen@vumc.nl
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MeSH Terms
Descriptor/Qualifier:
Animals
Biomechanics
Body Fluids / metabolism*
Intervertebral Disk / metabolism,  physiology*
Lumbar Vertebrae*
Osmotic Pressure
Swine
Weight-Bearing / physiology

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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