Design of spinous process hooks for flexible fixation of the lumbar spine

J C Leahy, K J Mathias, A Heaton, D E T Shepherd, D W L Hukins, Wiliam F Deans, M W Brian, D Wardlaw

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

A prototype flexible fixation system for the lumbar spine was subjected to tensile testing to failure and cyclic tensile testing in order to determine any regions of weakness. The system consisted of a spinous process hook and two laminar hooks made of stainless steel (316L). Each laminar hook was attached to the spinous process hook by a loop of polyester braid secured by a crimped metal sleeve. In five tensile tests, the system failed by irreversible deformation of the spinous process hook at 2.5 +/- 0.3 kN (mean +/- standard deviation). In three cyclic tests, in which the applied tension varied sinusoidally between 0.04 and 0.3 kN at a frequency of 5 Hz, failure occurred after less than 400 000 loading cycles. This occurred as a result of fatigue crack initiation and propagation in the spinous process hook. A finite element model showed a stress concentration in the region where the crack occurred, which raised the applied stress above the tensile fatigue strength of this stainless steel. The spinous process hook was redesigned for manufacture in a titanium alloy (Ti-6Al-4V ELI) to minimize artefacts in magnetic resonance imaging. Further finite element models showed no unacceptable stress concentrations.

Original languageEnglish
Pages (from-to)479-487
Number of pages9
JournalProceedings of the Institution of Mechanical Engineers. Part H, Journal of Engineering in Medicine
Volume214
Publication statusPublished - 2000

Keywords

  • finite element modelling
  • spine
  • flexible stabilization
  • mechanical testing
  • FACET SYNDROME
  • STABILIZATION
  • SYSTEM

Cite this

Design of spinous process hooks for flexible fixation of the lumbar spine. / Leahy, J C ; Mathias, K J ; Heaton, A ; Shepherd, D E T ; Hukins, D W L ; Deans, Wiliam F; Brian, M W ; Wardlaw, D .

In: Proceedings of the Institution of Mechanical Engineers. Part H, Journal of Engineering in Medicine, Vol. 214, 2000, p. 479-487.

Research output: Contribution to journalArticle

Leahy, J C ; Mathias, K J ; Heaton, A ; Shepherd, D E T ; Hukins, D W L ; Deans, Wiliam F ; Brian, M W ; Wardlaw, D . / Design of spinous process hooks for flexible fixation of the lumbar spine. In: Proceedings of the Institution of Mechanical Engineers. Part H, Journal of Engineering in Medicine. 2000 ; Vol. 214. pp. 479-487.
@article{fb57f319471a4256b48ce2155682bc99,
title = "Design of spinous process hooks for flexible fixation of the lumbar spine",
abstract = "A prototype flexible fixation system for the lumbar spine was subjected to tensile testing to failure and cyclic tensile testing in order to determine any regions of weakness. The system consisted of a spinous process hook and two laminar hooks made of stainless steel (316L). Each laminar hook was attached to the spinous process hook by a loop of polyester braid secured by a crimped metal sleeve. In five tensile tests, the system failed by irreversible deformation of the spinous process hook at 2.5 +/- 0.3 kN (mean +/- standard deviation). In three cyclic tests, in which the applied tension varied sinusoidally between 0.04 and 0.3 kN at a frequency of 5 Hz, failure occurred after less than 400 000 loading cycles. This occurred as a result of fatigue crack initiation and propagation in the spinous process hook. A finite element model showed a stress concentration in the region where the crack occurred, which raised the applied stress above the tensile fatigue strength of this stainless steel. The spinous process hook was redesigned for manufacture in a titanium alloy (Ti-6Al-4V ELI) to minimize artefacts in magnetic resonance imaging. Further finite element models showed no unacceptable stress concentrations.",
keywords = "finite element modelling, spine, flexible stabilization, mechanical testing, FACET SYNDROME, STABILIZATION, SYSTEM",
author = "Leahy, {J C} and Mathias, {K J} and A Heaton and Shepherd, {D E T} and Hukins, {D W L} and Deans, {Wiliam F} and Brian, {M W} and D Wardlaw",
year = "2000",
language = "English",
volume = "214",
pages = "479--487",
journal = "Proceedings of the Institution of Mechanical Engineers. Part H, Journal of Engineering in Medicine",
issn = "0954-4119",
publisher = "SAGE Publications Ltd",

}

TY - JOUR

T1 - Design of spinous process hooks for flexible fixation of the lumbar spine

AU - Leahy, J C

AU - Mathias, K J

AU - Heaton, A

AU - Shepherd, D E T

AU - Hukins, D W L

AU - Deans, Wiliam F

AU - Brian, M W

AU - Wardlaw, D

PY - 2000

Y1 - 2000

N2 - A prototype flexible fixation system for the lumbar spine was subjected to tensile testing to failure and cyclic tensile testing in order to determine any regions of weakness. The system consisted of a spinous process hook and two laminar hooks made of stainless steel (316L). Each laminar hook was attached to the spinous process hook by a loop of polyester braid secured by a crimped metal sleeve. In five tensile tests, the system failed by irreversible deformation of the spinous process hook at 2.5 +/- 0.3 kN (mean +/- standard deviation). In three cyclic tests, in which the applied tension varied sinusoidally between 0.04 and 0.3 kN at a frequency of 5 Hz, failure occurred after less than 400 000 loading cycles. This occurred as a result of fatigue crack initiation and propagation in the spinous process hook. A finite element model showed a stress concentration in the region where the crack occurred, which raised the applied stress above the tensile fatigue strength of this stainless steel. The spinous process hook was redesigned for manufacture in a titanium alloy (Ti-6Al-4V ELI) to minimize artefacts in magnetic resonance imaging. Further finite element models showed no unacceptable stress concentrations.

AB - A prototype flexible fixation system for the lumbar spine was subjected to tensile testing to failure and cyclic tensile testing in order to determine any regions of weakness. The system consisted of a spinous process hook and two laminar hooks made of stainless steel (316L). Each laminar hook was attached to the spinous process hook by a loop of polyester braid secured by a crimped metal sleeve. In five tensile tests, the system failed by irreversible deformation of the spinous process hook at 2.5 +/- 0.3 kN (mean +/- standard deviation). In three cyclic tests, in which the applied tension varied sinusoidally between 0.04 and 0.3 kN at a frequency of 5 Hz, failure occurred after less than 400 000 loading cycles. This occurred as a result of fatigue crack initiation and propagation in the spinous process hook. A finite element model showed a stress concentration in the region where the crack occurred, which raised the applied stress above the tensile fatigue strength of this stainless steel. The spinous process hook was redesigned for manufacture in a titanium alloy (Ti-6Al-4V ELI) to minimize artefacts in magnetic resonance imaging. Further finite element models showed no unacceptable stress concentrations.

KW - finite element modelling

KW - spine

KW - flexible stabilization

KW - mechanical testing

KW - FACET SYNDROME

KW - STABILIZATION

KW - SYSTEM

M3 - Article

VL - 214

SP - 479

EP - 487

JO - Proceedings of the Institution of Mechanical Engineers. Part H, Journal of Engineering in Medicine

JF - Proceedings of the Institution of Mechanical Engineers. Part H, Journal of Engineering in Medicine

SN - 0954-4119

ER -