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Article: Pure shear properties of lumbar spinal joints and the effect of tissue sectioning on load sharing.

TitlePure shear properties of lumbar spinal joints and the effect of tissue sectioning on load sharing.
Authors
Issue Date2005
PublisherHanley & Belfus, Inc. The Journal's web site is located at http://www.spinejournal.com
Citation
Spine, 2005, v. 30 n. 8, p. E204-E209 How to Cite?
AbstractSTUDY DESIGN: An in vitro biomechanical study on lumbar intervertebral joints. OBJECTIVES: To examine the mechanical properties of lumbar motion segments under pure shear loading and establish whether a simple model for functional differentiation between the anterior column and the posterior elements is applicable. SUMMARY OF BACKGROUND DATA: Anteroposterior shear has been implicated as a major factor in spinal instability. There is a substantial amount of data on shear motion as a coupled part of flexion-extension; data on the pure shear properties of intervertebral joints is limited. METHODS: Eighteen human cadaver lumbar motion segments were subject to nondestructive testing under pure shear loads (anterior shear and posterior shear). An MTS standard testing machine was used to record the load-deformation characteristics of specimens subject to deformation at a constant rate to a maximum shear load of approximately 250 N. Tissue sectioning was then performed with the specimen mounted in the testing machine. Eight specimens were sectioned through the intervertebral disc, including the anterior and posterior longitudinal ligaments, and 8 specimens were sectioned through the pedicles to remove the posterior elements. The same deformation pattern applied to the intact specimen was then reapplied to the sectioned specimen, and the load-deformation characteristics following sectioning were evaluated. RESULTS: The shear stiffness of the intact segments were found to be higher in anterior shear (mean group A = 583.8, B = 607 N/mm) than in posterior shear (mean group A = 469, B = 438.4 N/mm). Section of the anterior column and adjacent longitudinal ligaments resulted in a mean stiffness decreased by 22.8% of the intact value under anterior shear and 23.9% under posterior shear. Much larger change in shear stiffness was seen, and the mean sectioned stiffness dropped by 77.7% in anterior shear and 79% in posterior shear after removal of the posterior elements. After the anterior column was sectioned, 12% and 18% increases in the deformation for anterior and posterior directions were seen, whereas a distinct increase in the deformations was found after posterior elements sectioned. CONCLUSIONS: The posterior elements of the lumbar spine are more efficient in resisting anterior and posterior shear loads. However, the anterior column will exhibit similar load-displacement characteristics if subject to greater deformations. The sum of the normalized mean shear loads of the anterior column and posterior elements sustained at maximum intact deformation is significantly different from the shear load sustained by the intact spine at the same deformation. A simple concept of load sharing between the anterior column and the posterior elements may not be valid.
Persistent Identifierhttp://hdl.handle.net/10722/79614
ISSN
ISI Accession Number ID

 

DC FieldValueLanguage
dc.contributor.authorLu, WWen_HK
dc.contributor.authorLuk, KDen_HK
dc.contributor.authorHolmes, ADen_HK
dc.contributor.authorCheung, KMen_HK
dc.contributor.authorLeong, JCen_HK
dc.date.accessioned2010-09-06T07:56:38Z-
dc.date.available2010-09-06T07:56:38Z-
dc.date.issued2005en_HK
dc.identifier.citationSpine, 2005, v. 30 n. 8, p. E204-E209en_HK
dc.identifier.issn1528-1159en_HK
dc.identifier.urihttp://hdl.handle.net/10722/79614-
dc.description.abstractSTUDY DESIGN: An in vitro biomechanical study on lumbar intervertebral joints. OBJECTIVES: To examine the mechanical properties of lumbar motion segments under pure shear loading and establish whether a simple model for functional differentiation between the anterior column and the posterior elements is applicable. SUMMARY OF BACKGROUND DATA: Anteroposterior shear has been implicated as a major factor in spinal instability. There is a substantial amount of data on shear motion as a coupled part of flexion-extension; data on the pure shear properties of intervertebral joints is limited. METHODS: Eighteen human cadaver lumbar motion segments were subject to nondestructive testing under pure shear loads (anterior shear and posterior shear). An MTS standard testing machine was used to record the load-deformation characteristics of specimens subject to deformation at a constant rate to a maximum shear load of approximately 250 N. Tissue sectioning was then performed with the specimen mounted in the testing machine. Eight specimens were sectioned through the intervertebral disc, including the anterior and posterior longitudinal ligaments, and 8 specimens were sectioned through the pedicles to remove the posterior elements. The same deformation pattern applied to the intact specimen was then reapplied to the sectioned specimen, and the load-deformation characteristics following sectioning were evaluated. RESULTS: The shear stiffness of the intact segments were found to be higher in anterior shear (mean group A = 583.8, B = 607 N/mm) than in posterior shear (mean group A = 469, B = 438.4 N/mm). Section of the anterior column and adjacent longitudinal ligaments resulted in a mean stiffness decreased by 22.8% of the intact value under anterior shear and 23.9% under posterior shear. Much larger change in shear stiffness was seen, and the mean sectioned stiffness dropped by 77.7% in anterior shear and 79% in posterior shear after removal of the posterior elements. After the anterior column was sectioned, 12% and 18% increases in the deformation for anterior and posterior directions were seen, whereas a distinct increase in the deformations was found after posterior elements sectioned. CONCLUSIONS: The posterior elements of the lumbar spine are more efficient in resisting anterior and posterior shear loads. However, the anterior column will exhibit similar load-displacement characteristics if subject to greater deformations. The sum of the normalized mean shear loads of the anterior column and posterior elements sustained at maximum intact deformation is significantly different from the shear load sustained by the intact spine at the same deformation. A simple concept of load sharing between the anterior column and the posterior elements may not be valid.en_HK
dc.languageengen_HK
dc.publisherHanley & Belfus, Inc. The Journal's web site is located at http://www.spinejournal.comen_HK
dc.relation.ispartofSpineen_HK
dc.titlePure shear properties of lumbar spinal joints and the effect of tissue sectioning on load sharing.en_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0887-9869&volume=30&issue=8&spage=E204&epage=E209&date=2005&atitle=Pure+shear+properties+of+lumbar+spinal+joints+and+the+effect+of+tissue+sectioning+on+load+sharingen_HK
dc.identifier.emailLu, WW:wwlu@hku.hken_HK
dc.identifier.emailLuk, KD:hcm21000@hku.hken_HK
dc.identifier.emailCheung, KM:cheungmc@hku.hken_HK
dc.identifier.authorityLu, WW=rp00411en_HK
dc.identifier.authorityLuk, KD=rp00333en_HK
dc.identifier.authorityCheung, KM=rp00387en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.pmid15834318-
dc.identifier.scopuseid_2-s2.0-33644877933en_HK
dc.identifier.hkuros104331en_HK
dc.identifier.volume30en_HK
dc.identifier.issue8en_HK
dc.identifier.spageE204en_HK
dc.identifier.epageE209en_HK
dc.identifier.isiWOS:000228473400023-
dc.identifier.scopusauthoridLu, WW=7404215221en_HK
dc.identifier.scopusauthoridLuk, KD=7201921573en_HK
dc.identifier.scopusauthoridHolmes, AD=7401687268en_HK
dc.identifier.scopusauthoridCheung, KM=7402406754en_HK
dc.identifier.scopusauthoridLeong, JC=35560782200en_HK

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