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Johnson ME, Karges-Brown JR, Brismée JM, Brenza TM, Piper AK. Innovative seated vertical lumbar traction allows simultaneous computer work while inducing spinal height changes similar to supine lying. J Back Musculoskelet Rehabil 2023; 36:739-749. [PMID: 36641660 DOI: 10.3233/bmr-220202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
BACKGROUND Lumbar intervertebral disc height loss has been associated with spinal height change (SHC) and low back pain (LBP), including stenosis. Non-invasive methods to improve disc height loss require forms of lying down, which are unconducive to computer work. OBJECTIVE Intermittent vertical traction (VT) integrated with seated computer work may provide ergonomic alternatives for increasing SHC to promote LBP relief. The primary aim was to develop and introduce a safe VT prototype and dosage to induce and measure SHC. Prototype comfort and LBP ratings were exploratory secondary aims. METHODS Forty-one participants were stadiometry-measured for pre- and post-intervention SHC from seated VT at 35% body weight removed, supine lying (SL), and sitting at a computer (SIT) without VT. Pain ratings were recorded for those self-reporting LBP. VT prototype evaluations were compiled from a 3-question, 7-point Likert-style survey. RESULTS SHC increased by 3.9 ± 3.4 mm in VT, 1.7 ± 3.4 mm in SIT, and 4.3 ± 3.1 mm in SL (P< 0.000). Post hoc findings were significant between VT and SIT (P< 0.000), and SL and SIT (P< 0.000). VT and SL LBP ratings both decreased, but not SIT. CONCLUSION Intermittent seated VT is a promising alternative for postural relief during seated computer work, producing SHC similar to lying down without compromising workflow.
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Affiliation(s)
- Marit E Johnson
- Biomedical Engineering Graduate Program, South Dakota School of Mines and Technology, Rapid City, SD, USA
| | - Joy R Karges-Brown
- Department of Physical Therapy, University of South Dakota, Sanford Coyote Sports Center, Vermillion, SD, USA
| | - Jean-Michel Brismée
- Center for Rehabilitation Research, Department of Rehabilitation Sciences, Texas Tech University Health Sciences Center, Lubbock, Texas, USA
| | - Timothy M Brenza
- Biomedical Engineering Graduate Program, South Dakota School of Mines and Technology, Rapid City, SD, USA.,Department of Chemical and Biological Engineering, South Dakota School of Mines and Technology, Rapid City, SD, USA
| | - Adam K Piper
- Biomedical Engineering Graduate Program, South Dakota School of Mines and Technology, Rapid City, SD, USA.,Department of Industrial Engineering, South Dakota School of Mines and Technology, Rapid City, SD, USA
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Widmer J, Cornaz F, Farshad-Amacker NA, Snedeker JG, Spirig MJM, Farshad M. Hydrostatic integrity of the intervertebral disc assessed by MRI. J Biomech 2021; 127:110661. [PMID: 34391131 DOI: 10.1016/j.jbiomech.2021.110661] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 07/27/2021] [Accepted: 07/28/2021] [Indexed: 11/25/2022]
Abstract
Hydrostatic integrity of the intervertebral disc (IVD) is lost during the process of degeneration. Invasive pressure profilometry (IPP) can quantify it, however, is not applicable for clinical use. We aimed to investigate correlations between IPP and MRI findings to assess non-invasive MRI based methods for prediction of hydrostatic integrity of the intervertebral disc. The pressure profiles of 39 lumbar spinal segments originating from 22 human cadavers were recorded during axial compression in the neutral, the flexed and the extended positions. Disc pressure profiles were measured and mathematically transformed to a novel metric that quantifies pressure profile heterogeneity across the disc. The relationship between pressure profile inhomogeneity ("pressure score") and clinically established magnetic resonance-based classifications systems and demographic parameters was then tested using Spearman correlation tests. Pressure profile inhomogeneities were correlated with IVD degeneration (according to Pfirrmann, rho = 0.43, p = 0.006), endplate defects (according to Rajasekaran, rho = 0.39, p = 0.013), segmental degeneration (according to Farshad, rho = 0.41, p = 0.009) and age (rho = 0.32, p = 0.049). Modic changes per se did not affect the pressure profiles significantly (p = 0.23) and pressure scores did not correlate with BMI (rho = -0.21, p = 0.2). Heterogeneity of segmental IVD pressure profiles is a unique measure of disc function. We demonstrate that established clinical methods for MRI characterization of the intervertebral disc, the endplate and overall segmental degeneration all correlate with the hydrostatic integrity of the IVD and can be used for its assessment.
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Affiliation(s)
- Jonas Widmer
- Department of Orthopaedics, Balgrist University Hospital, Zurich, Switzerland; Institute for Biomechanics, ETH Zurich, Zurich, Switzerland.
| | - Frédéric Cornaz
- Department of Orthopaedics, Balgrist University Hospital, Zurich, Switzerland; Institute for Biomechanics, ETH Zurich, Zurich, Switzerland
| | | | - Jess G Snedeker
- Department of Orthopaedics, Balgrist University Hospital, Zurich, Switzerland; Institute for Biomechanics, ETH Zurich, Zurich, Switzerland
| | | | - Mazda Farshad
- Department of Orthopaedics, Balgrist University Hospital, Zurich, Switzerland
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Yang B, Wendland MF, O'Connell GD. Direct Quantification of Intervertebral Disc Water Content Using MRI. J Magn Reson Imaging 2020; 52:1152-1162. [DOI: 10.1002/jmri.27171] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 03/30/2020] [Accepted: 03/31/2020] [Indexed: 12/22/2022] Open
Affiliation(s)
- Bo Yang
- Department of Mechanical Engineering University of California Berkeley California USA
| | | | - Grace D. O'Connell
- Department of Mechanical Engineering University of California Berkeley California USA
- Department of Orthopaedic Surgery University of California San Francisco California USA
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Berry DB, Hernandez A, Onodera K, Ingram N, Ward SR, Gombatto SP. Lumbar spine angles and intervertebral disc characteristics with end-range positions in three planes of motion in healthy people using upright MRI. J Biomech 2019; 89:95-104. [PMID: 31047693 DOI: 10.1016/j.jbiomech.2019.04.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Revised: 04/02/2019] [Accepted: 04/12/2019] [Indexed: 12/17/2022]
Abstract
Understanding changes in lumbar spine (LS) angles and intervertebral disc (IVD) behavior in end-range positions in healthy subjects can provide a basis for developing more specific LS models and comparing people with spine pathology. The purposes of this study are to quantify 3D LS angles and changes in IVD characteristics with end-range positions in 3 planes of motion using upright MRI in healthy people, and to determine which intervertebral segments contribute most in each plane of movement. Thirteen people (average age = 24.4 years, range 18-51 years; 9 females; BMI = 22.4 ± 1.8 kg/m2) with no history of low back pain were scanned in an upright MRI in standing, sitting flexion, sitting axial rotation (left, right), prone on elbows, prone extension, and standing lateral bending (left, right). Global and local intervertebral LS angles were measured. Anterior-posterior length of the IVD and location of the nucleus pulposus was measured. For the sagittal plane, lower LS segments contribute most to change in position, and the location of the nucleus pulposus migrated from a more posterior position in sitting flexion to a more anterior position in end-range extension. For lateral bending, the upper LS contributes most to end-range positions. Small degrees of intervertebral rotation (1-2°) across all levels were observed for axial plane positions. There were no systematic changes in IVD characteristics for axial or coronal plane positions.
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Affiliation(s)
- David B Berry
- Department of Bioengineering, University of California San Diego, La Jolla, CA, USA
| | - Alejandra Hernandez
- Doctor of Physical Therapy Program, School of Exercise and Nutritional Sciences, San Diego State University, San Diego, CA, USA
| | - Keenan Onodera
- Department of Orthopaedic Surgery, University of California San Diego, La Jolla, CA, USA
| | - Noah Ingram
- Doctor of Physical Therapy Program, School of Exercise and Nutritional Sciences, San Diego State University, San Diego, CA, USA
| | - Samuel R Ward
- Department of Bioengineering, University of California San Diego, La Jolla, CA, USA; Department of Orthopaedic Surgery, University of California San Diego, La Jolla, CA, USA; Department of Radiology, University of California San Diego, La Jolla, CA, USA
| | - Sara P Gombatto
- Doctor of Physical Therapy Program, School of Exercise and Nutritional Sciences, San Diego State University, San Diego, CA, USA.
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Axial loading during MRI reveals deviant characteristics within posterior IVD regions between low back pain patients and controls. EUROPEAN SPINE JOURNAL : OFFICIAL PUBLICATION OF THE EUROPEAN SPINE SOCIETY, THE EUROPEAN SPINAL DEFORMITY SOCIETY, AND THE EUROPEAN SECTION OF THE CERVICAL SPINE RESEARCH SOCIETY 2018; 27:2840-2846. [PMID: 30302541 DOI: 10.1007/s00586-018-5774-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 08/27/2018] [Accepted: 09/19/2018] [Indexed: 12/14/2022]
Abstract
PURPOSE To investigate differences in functional intervertebral disk (IVD) characteristics between low back pain (LBP) patients and controls using T2-mapping with axial loading during MRI (alMRI). METHODS In total, 120 IVDs in 24 LBP patients (mean age 39 years, range 25-69) were examined with T2-mapping without loading of the spine (uMRI) and with alMRI (DynaWell® loading device) and compared with 60 IVDs in 12 controls (mean age 38 years, range 25-63). The IVD T2-value was acquired after 20-min loading in five regions of interests (ROI), ROI1-5 from anterior to posterior. T2-values were compared between loading states and cohorts with adjustment for Pfirrmann grade. RESULTS In LBP patients, mean T2-value of the entire IVD was 64 ms for uMRI and 66 ms for alMRI (p = 0.03) and, in controls, 65 ms and 65 ms (p = 0.5). Load-induced T2-differences (alMRI-uMRI) were seen in all ROIs in both patients (0.001 > p < 0.005) and controls (0.0001 > p < 0.03). In patients, alMRI induced an increase in T2-value for ROI1-3 (23%, 18% and 5%) and a decrease for ROI4 (3%) and ROI5 (24%). More pronounced load-induced decrease was detected in ROI4 in controls (9%/p = 0.03), while a higher absolute T2-value was found for ROI5 during alMRI in patients (38 ms) compared to controls (33 ms) (p = 0.04). CONCLUSION The alMRI-induced differences in T2-value in ROI4 and ROI5 between patients and controls most probably indicate biomechanical impairment in the posterior IVD regions. Hence, alMRI combined with T2-mapping offers an objective and clinical feasible tool for biomechanical IVD characterization that may deepen the knowledge regarding how LBP is related to altered IVD matrix composition. These slides can be retrieved under Electronic Supplementary Material.
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Chetoui MA, Boiron O, Ghiss M, Dogui A, Deplano V. Assessment of intervertebral disc degeneration-related properties using finite element models based on
$$\uprho _H$$
ρ
H
-weighted MRI data. Biomech Model Mechanobiol 2018; 18:17-28. [DOI: 10.1007/s10237-018-1064-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 07/24/2018] [Indexed: 12/22/2022]
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Velísková P, Bashkuev M, Shirazi-Adl A, Schmidt H. Computational study of the role of fluid content and flow on the lumbar disc response in cyclic compression: Replication of in vitro and in vivo conditions. J Biomech 2018; 70:16-25. [DOI: 10.1016/j.jbiomech.2017.10.032] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 10/18/2017] [Accepted: 10/27/2017] [Indexed: 10/18/2022]
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Li LY, Wu XL, Roman RJ, Fan F, Qiu CS, Chen BH. Diffusion-weighted 7.0T Magnetic Resonance Imaging in Assessment of Intervertebral Disc Degeneration in Rats. Chin Med J (Engl) 2018; 131:63-68. [PMID: 29271382 PMCID: PMC5754960 DOI: 10.4103/0366-6999.221261] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Background: Intervertebral disc degeneration (IDD) is a major cause of disc protrusion, likely to be associated with decrease of water content. This research aimed to evaluate IDD by diffusion-weighted imaging (DWI) with a 7.0 Tesla (T) magnetic resonance imaging (MRI) machine. Methods: A total of 24 healthy Sprague-Dawley rats were randomly selected and divided into four groups (A, B, C, and D), each consisting of 3 male and 3 female rats (28, 42, 56, and 70 days old, respectively). All the rats were imaged with a 7.0T MRI, producing T2WI, T1WI, and functional DWI sequences. Data were collected and apparent diffusion coefficient (ADC) charts were constructed. Nucleus pulposus and annulus fibrosus regions were identified, several regions of interest were chosen, and their ADC values were obtained. After imaging, rats were sacrificed and their intervertebral discs (L1–L6) were dissected, yielding a total of 144 discs. Protein was extracted for the purpose of Western blotting. Comparison among multiple samples used one-way analysis of variance and least significant difference methods. Results: 7.0T MRI revealed evident decrease in signal intensity within intervertebral discs of Sprague-Dawley rats with age. Intervertebral disc ADC values significantly decreased from Group A (0.00154 ± 0.00008) to Group D (0.00107 ± 0.00007; P < 0.01); nucleus pulposus ADC values significantly decreased from Group A (0.00164 ± 0.00005) to Group D (0.00140 ± 0.00007; P < 0.01) and annulus fibrosus ADC values significantly decreased from Group A (0.00129 ± 0.00014) to Group D (0.00082 ± 0.00012; P < 0.01). Meanwhile, it also revealed evident decrease from high spinal level to low spinal level: nucleus pulposus ADC values in Group A significantly decreased from L1/L2 (0.00163 ± 0.00006) to L6/S1 (0.00139 ± 0.00004; P < 0.01). While annulus fibrosus ADC values did not differ significantly between levels in Group A (P > 0.05). Western blotting showed that aggrecan content of intervertebral discs decreased from Group A (1.88 ± 0.16) to Group D (0.17 ± 0.04) with age (P < 0.01); Type II collagen content of intervertebral discs decreased from Group A (2.22 ± 0.04) to Group D (0.20 ± 0.01) with age (P < 0.01). No significant differences in aggrecan and Type II collagen content of L1–L6 intervertebral discs in Group A were noted (P > 0.05). Mean ADC values of different intervertebral regions were positively correlated with aggrecan and Type II collagen content (aggrecan: r = 0.631, P < 0.01; Type II collagen: r = 0.680, P < 0.01). Conclusion: 7.0T MRI-DWI could be applied to effectively diagnose and research early IDD in tiny variations.
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Affiliation(s)
- Long-Yang Li
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, MS 39216, USA
| | - Xiao-Lin Wu
- Department of Orthopedics, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266003, China
| | - Richard J Roman
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, MS 39216, USA
| | - Fan Fan
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, MS 39216, USA
| | - Chen-Sheng Qiu
- Department of Orthopedics, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266003, China
| | - Bo-Hua Chen
- Department of Orthopedics, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266003, China
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Johnson ZI, Doolittle AC, Snuggs JW, Shapiro IM, Le Maitre CL, Risbud MV. TNF-α promotes nuclear enrichment of the transcription factor TonEBP/NFAT5 to selectively control inflammatory but not osmoregulatory responses in nucleus pulposus cells. J Biol Chem 2017; 292:17561-17575. [PMID: 28842479 DOI: 10.1074/jbc.m117.790378] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 08/03/2017] [Indexed: 01/07/2023] Open
Abstract
Intervertebral disc degeneration (IDD) causes chronic back pain and is linked to production of proinflammatory molecules by nucleus pulposus (NP) and other disc cells. Activation of tonicity-responsive enhancer-binding protein (TonEBP)/NFAT5 by non-osmotic stimuli, including proinflammatory molecules, occurs in cells involved in immune response. However, whether inflammatory stimuli activate TonEBP in NP cells and whether TonEBP controls inflammation during IDD is unknown. We show that TNF-α, but not IL-1β or LPS, promoted nuclear enrichment of TonEBP protein. However, TNF-α-mediated activation of TonEBP did not cause induction of osmoregulatory genes. RNA sequencing showed that 8.5% of TNF-α transcriptional responses were TonEBP-dependent and identified genes regulated by both TNF-α and TonEBP. These genes were over-enriched in pathways and diseases related to inflammatory response and inhibition of matrix metalloproteases. Based on RNA-sequencing results, we further investigated regulation of novel TonEBP targets CXCL1, CXCL2, and CXCL3 TonEBP acted synergistically with TNF-α and LPS to induce CXCL1-proximal promoter activity. Interestingly, this regulation required a highly conserved NF-κB-binding site but not a predicted TonE, suggesting cross-talk between these two members of the Rel family. Finally, analysis of human NP tissue showed that TonEBP expression correlated with canonical osmoregulatory targets TauT/SLC6A6, SMIT/SLC5A3, and AR/AKR1B1, supporting in vitro findings that the inflammatory milieu during IDD does not interfere with TonEBP osmoregulation. In summary, whereas TonEBP participates in the proinflammatory response to TNF-α, therapeutic strategies targeting this transcription factor for treatment of disc disease must spare osmoprotective, prosurvival, and matrix homeostatic activities.
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Affiliation(s)
- Zariel I Johnson
- From the Department of Orthopaedic Surgery, Thomas Jefferson University, Philadelphia, Pennsylvania 19107 and
| | - Alexandra C Doolittle
- From the Department of Orthopaedic Surgery, Thomas Jefferson University, Philadelphia, Pennsylvania 19107 and
| | - Joseph W Snuggs
- the Biomolecular Sciences Research Centre, Sheffield Hallam University, S1 1WB Sheffield, United Kingdom
| | - Irving M Shapiro
- From the Department of Orthopaedic Surgery, Thomas Jefferson University, Philadelphia, Pennsylvania 19107 and
| | - Christine L Le Maitre
- the Biomolecular Sciences Research Centre, Sheffield Hallam University, S1 1WB Sheffield, United Kingdom
| | - Makarand V Risbud
- From the Department of Orthopaedic Surgery, Thomas Jefferson University, Philadelphia, Pennsylvania 19107 and
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Schmidt H, Reitmaier S, Graichen F, Shirazi-Adl A. Review of the fluid flow within intervertebral discs - How could in vitro measurements replicate in vivo? J Biomech 2016; 49:3133-3146. [PMID: 27651134 DOI: 10.1016/j.jbiomech.2016.09.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 08/09/2016] [Accepted: 09/07/2016] [Indexed: 11/18/2022]
Abstract
By maintaining a balance between external mechanical loads and internal osmotic pressure, fluid content of intervertebral discs constantly alters causing fluctuations in disc hydration, height, diameter and pressure that govern disc temporal response. This paper reviews and discusses the relevant findings of earlier studies on the disc fluid flow with the aim to understand and remedy discrepancies between in vivo and in vitro observations. New results of finite element model studies are also exploited in order to help identify the likely causes for such differences and underlying mechanisms observed in vitro. In vivo measurements of changes in spinal height and disc fluid content/pressure via stadiometry, magnetic resonance imaging and intradiscal pressure measurements have been carried out. They have demonstrated that the disc volume, fluid content, height and nucleus pressure alter depending to a large extent on prior-current external load conditions. Although the diurnal loading lasts on average nearly twice longer than the subsequent resting (16 vs. 8h), the disc completely recovers its height and volume during the latter period through fluid inflow. In view of much longer periods required to recover disc height and pressure in vitro in ovine, porcine, caprine, bovine and rat discs, concerns have been raised on the fluid inflow through the endplates that might be hampered by clogged blood vessels post mortem. Analyses of discrepancies in the flow-dependent recoveries in vivo and in vitro highlight an excessive fluid content in the latter as a likely cause. To replicate in vivo conditions as closely as possible in vitro, preparation and preconditioning of specimens and/or pressure and osmolarity of the culture media in which specimens are immersed should hence be designed in a manner as to diminish disc hydration level and/or fluid transport.
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Affiliation(s)
- Hendrik Schmidt
- Julius Wolff Institute, Charité - Universitätsmedizin Berlin, Berlin, Germany.
| | - Sandra Reitmaier
- Julius Wolff Institute, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Friedmar Graichen
- Julius Wolff Institute, Charité - Universitätsmedizin Berlin, Berlin, Germany
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Image driven subject-specific finite element models of spinal biomechanics. J Biomech 2016; 49:919-925. [DOI: 10.1016/j.jbiomech.2016.02.025] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 02/04/2016] [Accepted: 02/05/2016] [Indexed: 11/20/2022]
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12
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Fluid-flow dependent response of intervertebral discs under cyclic loading: On the role of specimen preparation and preconditioning. J Biomech 2015; 49:846-856. [PMID: 26549766 DOI: 10.1016/j.jbiomech.2015.10.029] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 10/21/2015] [Indexed: 01/16/2023]
Abstract
In vivo during the day, intervertebral discs are loaded mainly in compression causing fluid and height losses that are subsequently fully recovered overnight due to fluid inflow under smaller compression. However, in vitro, fluid flow through the endplates, in particular fluid imbibition, is hampered possibly by blood clots formed post mortem. Despite earlier in vitro studies, it remains yet unclear if and how fluid flow conditions in vitro could properly emulate those in vivo. Effects of various preload magnitudes (no preload, 0.06 and 0.28 MPa) and disc-bone preparation conditions (e.g., w/o bony endplates) on disc height and nucleus pressure were investigated using 54 bovine specimens. Changes in specimen height and pressure at different nucleus locations were used as surrogate measures to assess the fluid content and flow within the discs. Under all investigated preparation conditions and preload magnitudes, no significant pressure recovery could be obtained during low loading phases, even without bony endplates. On the contrary, partial to full displacement recovery were reached in particular under 0.28 MPa preload. Results highlight the significant role of disc preload magnitude in disc height recovery during low loading periods. Attention should hence be given in future studies to the proper selection of preload magnitude and duration as well as the animal models used if in vivo response is intended to be replicated. Findings also indicate that flushing the endplates or injection of bone cement respectively neither facilitates nor impedes fluid flow into or out of the disc to a noticeable degree in this bovine disc model.
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