Flow-related mechanics of the intervertebral disc: the validity of an in vitro model

Albert J van der Veen, Margriet Mullender, Theo H Smit, Idsart Kingma, Jaap H van Dieën

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

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.

Original languageEnglish
Pages (from-to)E534-9
JournalSpine
Volume30
Issue number18
Publication statusPublished - 15 Sep 2005

Cite this

van der Veen, Albert J ; Mullender, Margriet ; Smit, Theo H ; Kingma, Idsart ; van Dieën, Jaap H. / Flow-related mechanics of the intervertebral disc : the validity of an in vitro model. In: Spine. 2005 ; Vol. 30, No. 18. pp. E534-9.
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abstract = "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.",
keywords = "Animals, Biomechanical Phenomena, Body Fluids/metabolism, In Vitro Techniques, Intervertebral Disc/metabolism, Lumbar Vertebrae, Osmotic Pressure, Swine, Weight-Bearing/physiology",
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journal = "Spine",
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Flow-related mechanics of the intervertebral disc : the validity of an in vitro model. / van der Veen, Albert J; Mullender, Margriet; Smit, Theo H; Kingma, Idsart; van Dieën, Jaap H.

In: Spine, Vol. 30, No. 18, 15.09.2005, p. E534-9.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Flow-related mechanics of the intervertebral disc

T2 - the validity of an in vitro model

AU - van der Veen, Albert J

AU - Mullender, Margriet

AU - Smit, Theo H

AU - Kingma, Idsart

AU - van Dieën, Jaap H

PY - 2005/9/15

Y1 - 2005/9/15

N2 - 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.

AB - 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.

KW - Animals

KW - Biomechanical Phenomena

KW - Body Fluids/metabolism

KW - In Vitro Techniques

KW - Intervertebral Disc/metabolism

KW - Lumbar Vertebrae

KW - Osmotic Pressure

KW - Swine

KW - Weight-Bearing/physiology

M3 - Article

VL - 30

SP - E534-9

JO - Spine

JF - Spine

SN - 0362-2436

IS - 18

ER -