Spatially distributed circumferential strain measurement in an artificial spinal disc using fibre Bragg gratings
Spatially distributed circumferential strain measurement in an artificial spinal disc using fibre Bragg gratings
Artificial disc replacements (ADRs) are orthopaedic implants designed to replace degenerated intervertebral discs, a common aetiology of chronic back pain. ADRs which emulate the biomechanics of the natural disc promote the natural physiological kinematics, which is important for minimising postoperative deterioration of surrounding structures. By quantifying and comparing the displacements and strains within the ADR and the natural disc, target values can be established for future biomimetic ADR designs. However, measuring internal strain in these devices can be challenging. To this end, this study presents a novel application of fibre optic strain sensing through the use of fibre Bragg gratings. In this proof-of-principle study, an ADR model was fabricated with an embedded fibre optic sensor and subjected to physiological loads. The ADR model consisted of an elastomeric ring reinforced with Kevlar fibre. This simulated the annulus fibrosus (AF) of the natural disc and was left either filled or unfilled with an elastomeric material which simulated the nucleus pulposus (NP) of the natural disc. Fixation of the disc to artificial bone was achieved using three pins on the superior face and three pins on the inferior face of the ADR. Using wavelength division multiplexing of the fibre Bragg gratings, the hoop strain within the AF was monitored with a spatial resolution of 10 mm. Measurements revealed local strain concentrations around the fixation points and that the nucleated configuration increased circumferential strain in the AF by over 10 times for a given axial displacement. The measured strain asymmetry was correlated with lateral bending angle with an accuracy of ±0.5 degrees, which could be applied to tracking changes to the range of motion in load-controlled bending tests, for example. With further development, this technology has the ability to assess future designs during pre-clinical testing.
Biomechanics, degenerative disc disease, intervertebral disc, artificial disc replacement, fibre optic sensing, fibre Bragg grating
Godfrey, Michael
f7811099-7bfe-4095-ae3f-d5e7f907b4d0
Jantzen, Senta Lisa
e532e171-8ea3-4576-8843-17d96a3995d4
Dickinson, Alex
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Taylor, Andy
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Browne, Martin
6578cc37-7bd6-43b9-ae5c-77ccb7726397
7 February 2025
Godfrey, Michael
f7811099-7bfe-4095-ae3f-d5e7f907b4d0
Jantzen, Senta Lisa
e532e171-8ea3-4576-8843-17d96a3995d4
Dickinson, Alex
10151972-c1b5-4f7d-bc12-6482b5870cad
Taylor, Andy
05a2a7fe-82e4-4960-9425-c09738cf93cb
Browne, Martin
6578cc37-7bd6-43b9-ae5c-77ccb7726397
Godfrey, Michael, Jantzen, Senta Lisa, Dickinson, Alex, Taylor, Andy and Browne, Martin
(2025)
Spatially distributed circumferential strain measurement in an artificial spinal disc using fibre Bragg gratings.
The Journal of Strain Analysis for Engineering Design.
(doi:10.1177/03093247251315512).
Abstract
Artificial disc replacements (ADRs) are orthopaedic implants designed to replace degenerated intervertebral discs, a common aetiology of chronic back pain. ADRs which emulate the biomechanics of the natural disc promote the natural physiological kinematics, which is important for minimising postoperative deterioration of surrounding structures. By quantifying and comparing the displacements and strains within the ADR and the natural disc, target values can be established for future biomimetic ADR designs. However, measuring internal strain in these devices can be challenging. To this end, this study presents a novel application of fibre optic strain sensing through the use of fibre Bragg gratings. In this proof-of-principle study, an ADR model was fabricated with an embedded fibre optic sensor and subjected to physiological loads. The ADR model consisted of an elastomeric ring reinforced with Kevlar fibre. This simulated the annulus fibrosus (AF) of the natural disc and was left either filled or unfilled with an elastomeric material which simulated the nucleus pulposus (NP) of the natural disc. Fixation of the disc to artificial bone was achieved using three pins on the superior face and three pins on the inferior face of the ADR. Using wavelength division multiplexing of the fibre Bragg gratings, the hoop strain within the AF was monitored with a spatial resolution of 10 mm. Measurements revealed local strain concentrations around the fixation points and that the nucleated configuration increased circumferential strain in the AF by over 10 times for a given axial displacement. The measured strain asymmetry was correlated with lateral bending angle with an accuracy of ±0.5 degrees, which could be applied to tracking changes to the range of motion in load-controlled bending tests, for example. With further development, this technology has the ability to assess future designs during pre-clinical testing.
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An_Optically_Instrumented_IVD
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godfrey-et-al-2025-spatially-distributed-circumferential-strain-measurement-in-an-artificial-spinal-disc-using-fibre
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Accepted/In Press date: 13 December 2024
Published date: 7 February 2025
Keywords:
Biomechanics, degenerative disc disease, intervertebral disc, artificial disc replacement, fibre optic sensing, fibre Bragg grating
Identifiers
Local EPrints ID: 498388
URI: http://eprints.soton.ac.uk/id/eprint/498388
ISSN: 0309-3247
PURE UUID: ba4d56ca-7656-4008-806c-b0f85a4c8afa
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Date deposited: 18 Feb 2025 17:30
Last modified: 30 Aug 2025 01:43
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Contributors
Author:
Michael Godfrey
Author:
Senta Lisa Jantzen
Author:
Andy Taylor
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