In vitro study of shear force on interbody implants

Hitchcock, R; Sears, W; Gillies, RM; Milthorpe, B; Walsh, WR

In vitro study of shear force on interbody implants

Hitchcock, R Sears, W Gillies, RM Milthorpe, B

Walsh, WR

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Publication Type:: Journal Article
Citation:: Journal of Spinal Disorders and Techniques, 2006, 19 (1), pp. 32 - 36
Issue Date:: 2006-02-01

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Field	Value	Language
dc.contributor.author	Hitchcock, R	en_US
dc.contributor.author	Sears, W	en_US
dc.contributor.author	Gillies, RM	en_US
dc.contributor.author	Milthorpe, B https://orcid.org/0000-0002-0867-9586	en_US
dc.contributor.author	Walsh, WR https://orcid.org/0000-0002-5023-6148	en_US
dc.date.issued	2006-02-01	en_US
dc.identifier.citation	Journal of Spinal Disorders and Techniques, 2006, 19 (1), pp. 32 - 36	en_US
dc.identifier.issn	1536-0652	en_US
dc.identifier.uri	http://hdl.handle.net/10453/9706
dc.description.abstract	OBJECTIVE: The lordosis of the lumbar spine and body weight result in significant shear forces through the lumbosacral disc spaces. These forces result in translational motion across the disc space, which is resisted but not completely abolished by pedicle screw stabilization. It is postulated that this motion may be a factor in the development of nonunion of lumbar interbody fusions. An in vitro study of the micromotion of porcine specimens implanted with serrated or smooth interbody spacers and subjected to shear forces under compressive preload was conducted to determine whether the surface serrations on vertebral interbody implants significantly resist shear forces and resulting sagittal translation. METHODS: Measurements of anterior vertebral translation were recorded on porcine cervical spine segments, subjected to 25 N of anteroposterior shear load while under a 300-N compressive preload. Baseline testing was performed on intact specimens and partially destabilized specimens (facet joints removed). Following partial discectomy, the specimens were divided into two groups for testing: one using smooth-surfaced and one using serrated interbody spacers. RESULTS: Under 25-N shear load, the specimens tested with the serrated spacers showed anterior vertebral translation of 0.046 ± 0.013 mm, whereas those tested with the smooth spacers measured 0.152 ± 0.075 mm (P < 0.01). CONCLUSIONS: The presence of surface serrations on the interbody implants significantly increased the resistance to shear forces in this model. In the clinical setting, we postulate that micromotion at interbody fusion sites will be substantially less when serrated implants are used and may help reduce the incidence of nonunion. Copyright © 2006 by Lippincott Williams & Wilkins.	en_US
dc.relation.ispartof	Journal of Spinal Disorders and Techniques	en_US
dc.relation.isbasedon	10.1097/01.bsd.0000173455.79280.e8	en_US
dc.subject.classification	Orthopedics	en_US
dc.subject.mesh	Cervical Vertebrae	en_US
dc.subject.mesh	Animals	en_US
dc.subject.mesh	Swine	en_US
dc.subject.mesh	Spinal Fusion	en_US
dc.subject.mesh	Prosthesis Design	en_US
dc.subject.mesh	Prostheses and Implants	en_US
dc.subject.mesh	Biomechanics	en_US
dc.subject.mesh	Biomechanical Phenomena	en_US
dc.title	In vitro study of shear force on interbody implants	en_US
dc.type	Journal Article
utslib.citation.volume	1	en_US
utslib.citation.volume	19	en_US
utslib.for	1103 Clinical Sciences	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Strength - CHT - Health Technologies
utslib.copyright.status	closed_access
pubs.issue	1	en_US
pubs.publication-status	Published	en_US
pubs.volume	19	en_US

Abstract:

OBJECTIVE: The lordosis of the lumbar spine and body weight result in significant shear forces through the lumbosacral disc spaces. These forces result in translational motion across the disc space, which is resisted but not completely abolished by pedicle screw stabilization. It is postulated that this motion may be a factor in the development of nonunion of lumbar interbody fusions. An in vitro study of the micromotion of porcine specimens implanted with serrated or smooth interbody spacers and subjected to shear forces under compressive preload was conducted to determine whether the surface serrations on vertebral interbody implants significantly resist shear forces and resulting sagittal translation. METHODS: Measurements of anterior vertebral translation were recorded on porcine cervical spine segments, subjected to 25 N of anteroposterior shear load while under a 300-N compressive preload. Baseline testing was performed on intact specimens and partially destabilized specimens (facet joints removed). Following partial discectomy, the specimens were divided into two groups for testing: one using smooth-surfaced and one using serrated interbody spacers. RESULTS: Under 25-N shear load, the specimens tested with the serrated spacers showed anterior vertebral translation of 0.046 ± 0.013 mm, whereas those tested with the smooth spacers measured 0.152 ± 0.075 mm (P < 0.01). CONCLUSIONS: The presence of surface serrations on the interbody implants significantly increased the resistance to shear forces in this model. In the clinical setting, we postulate that micromotion at interbody fusion sites will be substantially less when serrated implants are used and may help reduce the incidence of nonunion. Copyright © 2006 by Lippincott Williams & Wilkins.

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http://hdl.handle.net/10453/9706