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Yeni YN, Oravec D, Drost J, Zauel R, Flynn MJ. Stiffness and Strain Properties Derived From Digital Tomosynthesis-Based Digital Volume Correlation Predict Vertebral Strength Independently From Bone Mineral Density. J Biomech Eng 2023; 145:041009. [PMID: 36350266 PMCID: PMC9791669 DOI: 10.1115/1.4056196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 10/31/2022] [Indexed: 11/11/2022]
Abstract
Vertebral fractures are the most common osteoporotic fractures, but their prediction using standard bone mineral density (BMD) measurements from dual energy X-ray absorptiometry (DXA) is limited in accuracy. Stiffness, displacement, and strain distribution properties derived from digital tomosynthesis-based digital volume correlation (DTS-DVC) have been suggested as clinically measurable metrics of vertebral bone quality. However, the extent to which these properties correlate to vertebral strength is unknown. To establish this relationship, two independent experiments, one examining isolated T11 and the other examining L3 vertebrae within the L2-L4 segments from cadaveric donors were utilized. Following DXA and DTS imaging, the specimens were uniaxially compressed to fracture. BMD, bone mineral content (BMC), and bone area were recorded for the anteroposterior and lateromedial views from DXA, stiffness, endplate to endplate displacement and distribution statistics of intravertebral strains were calculated from DTS-DVC and vertebral strength was measured from mechanical tests. Regression models were used to examine the relationships of strength with the other variables. Correlations of BMD with vertebral strength varied between experimental groups (R2adj = 0.19-0.78). DTS-DVC derived properties contributed to vertebral strength independently from BMD measures (increasing R2adj to 0.64-0.95). DTS-DVC derived stiffness was the best single predictor (R2adj = 0.66, p < 0.0001) and added the most to BMD in models of vertebral strength for pooled T11 and L3 specimens (R2adj = 0.95, p < 0.0001). These findings provide biomechanical relevance to DTS-DVC calculated properties of vertebral bone and encourage further efforts in the development of the DTS-DVC approach as a clinical tool.
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Affiliation(s)
- Yener N. Yeni
- Bone & Joint Center, Henry Ford Hospital Integrative Biosciences Center (iBio), 6135 Woodward, Detroit, MI 48202
| | - Daniel Oravec
- Bone & Joint Center, Henry Ford Hospital Integrative Biosciences Center (iBio), 6135 Woodward, Detroit, MI 48202
| | - Joshua Drost
- Bone & Joint Center, Henry Ford Hospital Integrative Biosciences Center (iBio), 6135 Woodward, Detroit, MI 48202
| | - Roger Zauel
- Bone & Joint Center, Henry Ford Hospital Integrative Biosciences Center (iBio), 6135 Woodward, Detroit, MI 48202
| | - Michael J. Flynn
- Department of Radiology, Henry Ford Hospital, One Ford Place, Suite 2F, Detroit, MI 48202
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Costi JJ, Ledet EH, O'Connell GD. Spine biomechanical testing methodologies: The controversy of consensus vs scientific evidence. JOR Spine 2021; 4:e1138. [PMID: 33778410 PMCID: PMC7984003 DOI: 10.1002/jsp2.1138] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/01/2020] [Revised: 12/04/2020] [Accepted: 12/07/2020] [Indexed: 12/14/2022] Open
Abstract
Biomechanical testing methodologies for the spine have developed over the past 50 years. During that time, there have been several paradigm shifts with respect to techniques. These techniques evolved by incorporating state-of-the-art engineering principles, in vivo measurements, anatomical structure-function relationships, and the scientific method. Multiple parametric studies have focused on the effects that the experimental technique has on outcomes. As a result, testing methodologies have evolved, but there are no standard testing protocols, which makes the comparison of findings between experiments difficult and conclusions about in vivo performance challenging. In 2019, the international spine research community was surveyed to determine the consensus on spine biomechanical testing and if the consensus opinion was consistent with the scientific evidence. More than 80 responses to the survey were received. The findings of this survey confirmed that while some methods have been commonly adopted, not all are consistent with the scientific evidence. This review summarizes the scientific literature, the current consensus, and the authors' recommendations on best practices based on the compendium of available evidence.
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Affiliation(s)
- John J. Costi
- Biomechanics and Implants Research Group, Medical Device Research Institute, College of Science and EngineeringFlinders UniversityAdelaideAustralia
| | - Eric H. Ledet
- Department of Biomedical EngineeringRensselaer Polytechnic InstituteTroyNew YorkUSA
- Research and Development ServiceStratton VA Medical CenterAlbanyNew YorkUSA
| | - Grace D. O'Connell
- Department of Mechanical EngineeringUniversity of California‐BerkeleyBerkeleyCaliforniaUSA
- Department of Orthopaedic SurgeryUniversity of California‐San FranciscoSan FranciscoCaliforniaUSA
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Han MS, Lee SS, Lee SK, Jang JW, Moon BJ, Lee JK. Single-Stage Posterior Circumferential Stabilization Using Double Small Cages for the Treatment of Thoracic and Lumbar Spine Fractures. World Neurosurg 2020; 144:e701-e709. [PMID: 32949794 DOI: 10.1016/j.wneu.2020.09.047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 09/09/2020] [Accepted: 09/10/2020] [Indexed: 11/28/2022]
Abstract
OBJECTIVE Controversy remains regarding the optimal methods for resection of the vertebral body, reconstruction of the anterior column, and decompression of the spinal cord in patients who have severe vertebral body destruction of the thoracic or lumbar spine with associated neurologic impairment. We report an alternative technique for primary treatment and salvage involving single-stage corpectomy followed by reconstruction of the anterior column using double small mesh cages via the posterior-only approach. METHODS Plain radiographs and computed tomography scans, taken at different intervals, were used to measure local kyphosis, segmental height, and fusion grade. Pain was evaluated using the visual analog scale (VAS), and neurologic symptoms were classified according to Frankel grade. RESULTS The mean kyphotic deformity improved by 14.47 ± 9.06 degrees (P < 0.001), and the mean segmental height improved by 7.17 mm ± 6.11 mm (P < 0.001) after surgery. Fusion was achieved at 84% of patients, within a median interval of 12 months. Kyphotic recurrence was observed in 2 patients (11%), segmental height loss occurred in 1 patient (5%), and both kyphotic recurrence and segmental height loss occurred in 1 patient (5%). None of the patients reported worsening pain or neurologic symptoms after surgery, and there were no surgery-related complications such as neural injury, cerebrospinal fluid leakage, cage dislocation, surgical site infection, or cardiopulmonary complications. CONCLUSIONS Single-stage corpectomy followed by reconstruction of the anterior column using double small mesh cages via the posterior-only approach is a reliable and less invasive single-stage treatment and salvage option in selected cases.
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Affiliation(s)
- Moon-Soo Han
- Department of Neurosurgery, Chonnam National University Hospital and Medical School, Gwangju, South Korea
| | - Shin-Seok Lee
- Division of Rheumatology, Department of Internal Medicine, Chonnam National University Hospital and Medical School, Gwangju, South Korea
| | - Seul-Kee Lee
- Department of Neurosurgery, Chonnam National University Hospital and Medical School, Gwangju, South Korea
| | - Jae-Won Jang
- Department of Neurosurgery, Chonnam National University Hospital and Medical School, Gwangju, South Korea
| | - Bong Ju Moon
- Department of Neurosurgery, Chonnam National University Hospital and Medical School, Gwangju, South Korea
| | - Jung-Kil Lee
- Department of Neurosurgery, Chonnam National University Hospital and Medical School, Gwangju, South Korea.
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Hussein AI, Louzeiro DT, Unnikrishnan GU, Morgan EF. Differences in Trabecular Microarchitecture and Simplified Boundary Conditions Limit the Accuracy of Quantitative Computed Tomography-Based Finite Element Models of Vertebral Failure. J Biomech Eng 2019; 140:2665235. [PMID: 29196764 DOI: 10.1115/1.4038609] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Indexed: 11/08/2022]
Abstract
Vertebral fractures are common in the elderly, but efforts to reduce their incidence have been hampered by incomplete understanding of the failure processes that are involved. This study's goal was to elucidate failure processes in the lumbar vertebra and to assess the accuracy of quantitative computed tomography (QCT)-based finite element (FE) simulations of these processes. Following QCT scanning, spine segments (n = 27) consisting of L1 with adjacent intervertebral disks and neighboring endplates of T12 and L2 were compressed axially in a stepwise manner. A microcomputed tomography scan was performed at each loading step. The resulting time-lapse series of images was analyzed using digital volume correlation (DVC) to quantify deformations throughout the vertebral body. While some diversity among vertebrae was observed on how these deformations progressed, common features were large strains that developed progressively in the superior third and, concomitantly, in the midtransverse plane, in a manner that was associated with spatial variations in microstructural parameters such as connectivity density. Results of FE simulations corresponded qualitatively to the measured failure patterns when boundary conditions were derived from DVC displacements at the endplate. However, quantitative correspondence was often poor, particularly when boundary conditions were simplified to uniform compressive loading. These findings suggest that variations in trabecular microstructure are one cause of the differences in failure patterns among vertebrae and that both the lack of incorporation of these variations into QCT-based FE models and the oversimplification of boundary conditions limit the accuracy of these models in simulating vertebral failure.
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Affiliation(s)
- Amira I Hussein
- Department of Mechanical Engineering, Boston University, 110 Cummington Mall, Boston, MA 02215 e-mail:
| | - Daniel T Louzeiro
- Department of Mechanical Engineering, Boston University, Boston, MA 02215
| | | | - Elise F Morgan
- Department of Mechanical Engineering, Boston University, Boston, MA 02215
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Huang L, Korhonen RK, Turunen MJ, Finnilä MAJ. Experimental mechanical strain measurement of tissues. PeerJ 2019; 7:e6545. [PMID: 30867989 PMCID: PMC6409087 DOI: 10.7717/peerj.6545] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 01/31/2019] [Indexed: 12/22/2022] Open
Abstract
Strain, an important biomechanical factor, occurs at different scales from molecules and cells to tissues and organs in physiological conditions. Under mechanical strain, the strength of tissues and their micro- and nanocomponents, the structure, proliferation, differentiation and apoptosis of cells and even the cytokines expressed by cells probably shift. Thus, the measurement of mechanical strain (i.e., relative displacement or deformation) is critical to understand functional changes in tissues, and to elucidate basic relationships between mechanical loading and tissue response. In the last decades, a great number of methods have been developed and applied to measure the deformations and mechanical strains in tissues comprising bone, tendon, ligament, muscle and brain as well as blood vessels. In this article, we have reviewed the mechanical strain measurement from six aspects: electro-based, light-based, ultrasound-based, magnetic resonance-based and computed tomography-based techniques, and the texture correlation-based image processing method. The review may help solving the problems of experimental and mechanical strain measurement of tissues under different measurement environments.
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Affiliation(s)
- Lingwei Huang
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Rami K Korhonen
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Mikael J Turunen
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Mikko A J Finnilä
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.,Research Unit of Medical Imaging, Physics and Technology, University of Oulu, Oulu, Finland.,Medical Research Center Oulu, Oulu University Hospital, Oulu, Finland
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Danesi V, Erani P, Brandolini N, Juszczyk MM, Cristofolini L. Effect of the In Vitro Boundary Conditions on the Surface Strain Experienced by the Vertebral Body in the Elastic Regime. J Biomech Eng 2017; 138:2543312. [PMID: 27496676 DOI: 10.1115/1.4034383] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Indexed: 11/08/2022]
Abstract
The vertebral strength and strain can be assessed in vitro by both using isolated vertebrae and sets of three adjacent vertebrae (the central one is loaded through the disks). Our goal was to elucidate if testing single-vertebra-specimens in the elastic regime provides different surface strains to three-vertebrae-segments. Twelve three-vertebrae sets were extracted from thoracolumbar human spines. To measure the principal strains, the central vertebra of each segment was prepared with eight strain-gauges. The sets were tested mechanically, allowing comparison of the surface strains between the two boundary conditions: first when the same vertebra was loaded through the disks (three-vertebrae-segment) and then with the endplates embedded in cement (single-vertebra). They were all subjected to four nondestructive tests (compression, traction, torsion clockwise, and counterclockwise). The magnitude of principal strains differed significantly between the two boundary conditions. For axial loading, the largest principal strains (along vertebral axis) were significantly higher when the same vertebra was tested isolated compared to the three-vertebrae-segment. Conversely, circumferential strains decreased significantly in the single vertebrae compared to the three-vertebrae-segment, with some variations exceeding 100% of the strain magnitude, including changes from tension to compression. For torsion, the differences between boundary conditions were smaller. This study shows that, in the elastic regime, when the vertebra is loaded through a cement pot, the surface strains differ from when it is loaded through the disks. Therefore, when single vertebrae are tested, surface strain should be taken with caution.
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Clouthier AL, Hosseini HS, Maquer G, Zysset PK. Finite element analysis predicts experimental failure patterns in vertebral bodies loaded via intervertebral discs up to large deformation. Med Eng Phys 2015; 37:599-604. [PMID: 25922211 DOI: 10.1016/j.medengphy.2015.03.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 01/14/2015] [Accepted: 03/22/2015] [Indexed: 11/28/2022]
Abstract
Vertebral compression fractures are becoming increasingly common. Patient-specific nonlinear finite element (FE) models have shown promise in predicting yield strength and damage pattern but have not been experimentally validated for clinically relevant vertebral fractures, which involve loading through intervertebral discs with varying degrees of degeneration up to large compressive strains. Therefore, stepwise axial compression was applied in vitro on segments and performed in silico on their FE equivalents using a nonlocal damage-plastic model including densification at large compression for bone and a time-independent hyperelastic model for the disc. The ability of the nonlinear FE models to predict the failure pattern in large compression was evaluated for three boundary conditions: healthy and degenerated intervertebral discs and embedded endplates. Bone compaction and fracture patterns were predicted using the local volume change as an indicator and the best correspondence was obtained for the healthy intervertebral discs. These preliminary results show that nonlinear finite element models enable prediction of bone localisation and compaction. To the best of our knowledge, this is the first study to predict the collapse of osteoporotic vertebral bodies up to large compression using realistic loading via the intervertebral discs.
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Affiliation(s)
- Allison L Clouthier
- Institute for Surgical Technology and Biomechanics, University of Bern, Stauffacherstrasse 78, 3014 Bern, Switzerland.
| | - Hadi S Hosseini
- Institute for Surgical Technology and Biomechanics, University of Bern, Stauffacherstrasse 78, 3014 Bern, Switzerland.
| | - Ghislain Maquer
- Institute for Surgical Technology and Biomechanics, University of Bern, Stauffacherstrasse 78, 3014 Bern, Switzerland.
| | - Philippe K Zysset
- Institute for Surgical Technology and Biomechanics, University of Bern, Stauffacherstrasse 78, 3014 Bern, Switzerland.
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8
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Syahrom A, Abdul Kadir MR, Harun MN, Öchsner A. Permeability study of cancellous bone and its idealised structures. Med Eng Phys 2014; 37:77-86. [PMID: 25523865 DOI: 10.1016/j.medengphy.2014.11.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 09/03/2014] [Accepted: 11/05/2014] [Indexed: 11/29/2022]
Abstract
Artificial bone is a suitable alternative to autografts and allografts, however their use is still limited. Though there were numerous reports on their structural properties, permeability studies of artificial bones were comparably scarce. This study focused on the development of idealised, structured models of artificial cancellous bone and compared their permeability values with bone surface area and porosity. Cancellous bones from fresh bovine femur were extracted and cleaned following an established protocol. The samples were scanned using micro-computed tomography (μCT) and three-dimensional models of the cancellous bones were reconstructed for morphology study. Seven idealised and structured cancellous bone models were then developed and fabricated via rapid prototyping technique. A test-rig was developed and permeability tests were performed on the artificial and real cancellous bones. The results showed a linear correlation between the permeability and the porosity as well as the bone surface area. The plate-like idealised structure showed a similar value of permeability to the real cancellous bones.
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Affiliation(s)
- Ardiyansyah Syahrom
- Sport Innovation and Technology Center (SITC), Universiti Teknologi MalaysiaJ, Johor, Malaysia.
| | - Mohammed Rafiq Abdul Kadir
- Medical Device Technology Group, Faculty of Biomedical Engineering and Health Science, Universiti Teknologi Malaysia, Johor, Malaysia
| | - Muhamad Nor Harun
- Sport Innovation and Technology Center (SITC), Universiti Teknologi MalaysiaJ, Johor, Malaysia
| | - Andreas Öchsner
- Griffith School of Engineering, Griffith University, Australia
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Syahrom A, Abdul Kadir MR, Abdullah J, Öchsner A. Permeability studies of artificial and natural cancellous bone structures. Med Eng Phys 2013; 35:792-9. [DOI: 10.1016/j.medengphy.2012.08.011] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Revised: 07/17/2012] [Accepted: 08/17/2012] [Indexed: 11/25/2022]
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10
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Hussein AI, Mason ZD, Morgan EF. Presence of intervertebral discs alters observed stiffness and failure mechanisms in the vertebra. J Biomech 2013; 46:1683-8. [PMID: 23683319 DOI: 10.1016/j.jbiomech.2013.04.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Revised: 02/27/2013] [Accepted: 04/08/2013] [Indexed: 11/29/2022]
Abstract
Ex vivo mechanical testing is an essential tool for study of vertebral mechanics. However, the common method of testing vertebral bodies in the absence of adjacent intervertebral discs (IVDs) may limit the physiological relevance of the results. The goal of this study was to determine the influence of IVDs on vertebral mechanical properties and failure mechanisms. Rabbit thoracic vertebral bodies were tested with and without IVDs in a stepwise fashion that incorporated a micro-computed tomography scan at each loading step. The image sequences were analyzed using digital volume correlation to quantify deformations throughout the vertebral body. The observed deformation patterns differed substantially between the groups. Specimens tested with IVDs exhibited a slow increase in strain in the inferior and posterior regions, followed by a sudden increase in strain in the anterior cortex right at the yield point. In contrast, the highest strains in the isolated vertebral bodies were in the posterior regions throughout the test. Specimens tested with IVDs had lower stiffness (507.49±184.73N/mm vs. 845.61±296.09N/mm; p=0.044), higher ultimate displacement (2.00±0.68mm vs. 1.17±0.54mm; p=0.043), and higher maximum shear strains (e.g. top 25th percentile: 0.19±0.11 vs. 0.06±0.07mm/mm; p<0.0458), and tended to have lower ultimate force (690.28±160.25N vs. 873.81±131.48N; p=0.056). Similar work to failure (648.15±317.86N-mm vs. 603.49±437.95 N-mm; p=0.844) was observed between the two groups. These results indicate that testing vertebral bodies in the absence of IVDs can elicit artifactual failure mechanisms. These artifacts may be more prominent than the effects on vertebral strength and toughness.
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Affiliation(s)
- Amira I Hussein
- Department of Mechanical Engineering, Boston University, 110 Cummington Mall, Boston, MA 02215, USA.
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11
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Hardisty MR, Akens MK, Hojjat SP, Yee A, Whyne CM. Quantification of the effect of osteolytic metastases on bone strain within whole vertebrae using image registration. J Orthop Res 2012; 30:1032-9. [PMID: 22213180 DOI: 10.1002/jor.22045] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Accepted: 11/29/2011] [Indexed: 02/04/2023]
Abstract
The vertebral column is the most frequent site of metastatic involvement of the skeleton with up to 1/3 of all cancer patients developing spinal metastases. Longer survival times for patients, particularly secondary to breast cancer, have increased the need for better understanding the impact of skeletal metastases on structural stability. This study aims to apply image registration to calculate strain distributions in metastatically involved rodent vertebrae utilizing µCT imaging. Osteolytic vertebral lesions were developed in five rnu/rnu rats 2-3 weeks post intracardiac injection with MT-1 human breast cancer cells. An image registration algorithm was used to calculate and compare strain fields due to axial compressive loading in metastatically involved and control vertebrae. Tumor-bearing vertebrae had greatly increased compressive strains, double the magnitude of strain compared to control vertebrae (p=0.01). Qualitatively strain concentrated within the growth plates in both tumor bearing and control vertebrae. Most interesting was the presence of strain concentrations at the dorsal wall in metastatically involved vertebrae, suggesting structural instability. Strain distributions, quantified by image registration were consistent with known consequences of lytic involvement. Metastatically involved vertebrae had greater strain magnitude than control vertebrae. Strain concentrations at the dorsal wall in only the metastatic vertebrae, were consistent with higher incidence of burst fracture secondary to this pathology. Future use of image registration of whole vertebrae will allow focused examination of the efficacy of targeted and systemic treatments in reducing strains and the related risk of fracture in pathologic bones under simple and complex loading.
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Affiliation(s)
- Michael R Hardisty
- Orthopaedic Biomechanics Laboratory, Sunnybrook Health Sciences Centre, 2075 Bayview Ave., Room UB-19, University of Toronto, Toronto, Ontario, Canada
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Syahrom A, Abdul Kadir MR, Abdullah J, Öchsner A. Mechanical and microarchitectural analyses of cancellous bone through experiment and computer simulation. Med Biol Eng Comput 2011; 49:1393-403. [PMID: 21947767 DOI: 10.1007/s11517-011-0833-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Accepted: 09/08/2011] [Indexed: 10/17/2022]
Abstract
The relationship between microarchitecture to the failure mechanism and mechanical properties can be assessed through experimental and computational methods. In this study, both methods were utilised using bovine cadavers. Twenty four samples of cancellous bone were extracted from fresh bovine and the samples were cleaned from excessive marrow. Uniaxial compression testing was performed with displacement control. After mechanical testing, each specimen was ashed in a furnace. Four of the samples were exemplarily scanned using micro-computed tomography (μCT) and three dimensional models of the cancellous bones were reconstructed for finite element simulation. The mechanical properties and the failure modes obtained from numerical simulations were then compared to the experiments. Correlations between microarchitectural parameters to the mechanical properties and failure modes were then made. The Young's modulus correlates well with the bone volume fraction with R² = 0.615 and P value 0.013. Three different types of failure modes of cancellous bone were observed: oblique fracture (21.7%), perpendicular global fracture (47.8%), and scattered localised fracture (30.4%). However, no correlations were found between the failure modes to the morphological parameters. The percentage of error between computer predictions and the actual experimental test was from 6 to 12%. These mechanical properties and information on failure modes can be used for the development of synthetic cancellous bone.
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Affiliation(s)
- Ardiyansyah Syahrom
- Department of Solid Mechanics and Design, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Johor, Malaysia
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13
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Hojjat SP, Won E, Hardisty MR, Akens MK, Wise-Milestone LM, Whyne CM. Non-Destructive Evaluation of the Effects of Combined Bisphosphonate and Photodynamic Therapy on Bone Strain in Metastatic Vertebrae Using Image Registration. Ann Biomed Eng 2011; 39:2816-22. [DOI: 10.1007/s10439-011-0370-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Accepted: 07/23/2011] [Indexed: 11/29/2022]
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14
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Jang IG, Kim IY. Computational study on the effect of loading alteration caused by disc degeneration on the trabecular architecture in human lumbar spine. J Biomech 2010; 43:492-9. [DOI: 10.1016/j.jbiomech.2009.09.042] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Revised: 09/25/2009] [Accepted: 09/27/2009] [Indexed: 10/20/2022]
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15
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Harrison NM, McHugh PE. Comparison of trabecular bone behavior in core and whole bone samples using high-resolution modeling of a vertebral body. Biomech Model Mechanobiol 2010; 9:469-80. [PMID: 20066462 DOI: 10.1007/s10237-009-0188-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2008] [Accepted: 12/23/2009] [Indexed: 11/26/2022]
Abstract
Computational analysis of trabecular bone normally involves the modeling of (experimental tests of) cored samples. However, the lack of constraint on the sides of the extracted trabecular bone samples limits the information that can be inferred regarding true in situ behavior. Here, the element-by-element voxel-based finite element method was applied via, a custom-written software suite (FEEBE), to a 72 microm resolution model of an ovine vertebra. The difference between the apparent modulus of eight concentric core cylinders when modeled as part of the whole bone (containing 84 x 10(6) degrees of freedom) and independent of the whole bone was investigated. The results showed that cored trabecular bone apparent modulus depended significantly on the core diameter when modeled as an extracted core (r (2) = 0.975) and as part of a whole bone (r (2) = 0.986). The cause of this result was separated into the side-artifact effect and bone volume fraction (BV/TV) effect. For the independently modeled cores, the apparent modulus of an inner core region of interest varied with increasing thickness of the outer annulus. This was attributed to the side-artifact effect, given that the BV/TV of the core region was constant. Within the whole trabecular structure, the side artifact was eliminated as the entire bone structure was modeled. However, a BV/TV effect influenced the apparent modulus depending on the size of the core selected for determining apparent modulus. Changing the size of the core varied the overall BV/TV of the core, and this significantly (r (2) = 0.999) influences the apparent modulus. Therefore, determining a 'true' apparent modulus for trabecular bone was not achievable. The independently modeled cores consistently under-predict the in vivo apparent modulus. It is recommended that if a 'true' apparent modulus is required, the BV/TV at which it is required needs to be first determined. Apparent modeling of entire bones at microscale resolution allowed regions of low and high tissue strains to be identified, consistent with patterns of trabecular bone remodeling and resorption reported in literature. The basivertebral vein cavity underwent the highest strains within the entire vertebral body, suggesting that failure might initiate here, despite containing visibly thicker struts and plate trabeculae. Although computationally expensive, analysis of the entire vertebral body provided a full picture of in situ trabecular bone deformation.
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Affiliation(s)
- Noel M Harrison
- National Centre for Biomedical Engineering Science, National University of Ireland, Galway, Ireland.
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16
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Hardisty MR, Whyne CM. Whole Bone Strain Quantification by Image Registration: A Validation Study. J Biomech Eng 2009; 131:064502. [DOI: 10.1115/1.3127249] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Quantification of bone strain can be used to better understand fracture risk, bone healing, and bone turnover. The objective of this work was to develop and validate an intensity matching image registration method to accurately measure and spatially resolve strain in vertebrae using μCT imaging. A strain quantification method was developed that used two sequential μCT scans, taken in loaded and unloaded configurations. The image correlation algorithm implemented was a multiresolution intensity matching deformable registration that found a series of affine mapping between the unloaded and loaded scans. Once the registration was completed, the displacement field and strain field were calculated from the mappings obtained. Validation was done in two distinct ways: the first was to look at how well the method could quantify zero strain; the second was to look at how the method was able to reproduce a known applied strain field. Analytically defined strain fields that linearly varied in space and strain fields resulting from finite element analysis were used to test the strain measurement algorithm. The deformable registration method showed very good agreement with all cases imposed, establishing a detection limit of 0.0004 strain and displaying agreement with the imposed strain cases (average R2=0.96). The deformable registration routine developed was able to accurately measure both strain and displacement fields in whole rat vertebrae. A rigorous validation of any strain measurement method is needed that reports on the ability of the routine to measure strain in a variety of strain fields with differing spatial extents, within the structure of interest.
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Affiliation(s)
- Michael R. Hardisty
- Institute of Biomaterials and Biomedical Engineering, University of Toronto; Orthopaedic and Biomechanics Laboratory, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Room UB-19, Toronto, ON, M4N 3M5, Canada
| | - Cari M. Whyne
- Institute of Biomaterials and Biomedical Engineering, University of Toronto; Orthopaedic and Biomechanics Laboratory, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Room UB-19, Toronto, ON, M4N 3M5, Canada
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17
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Sciubba DM, Gallia GL, McGirt MJ, Woodworth GF, Garonzik IM, Witham T, Gokaslan ZL, Wolinsky JP. Thoracic kyphotic deformity reduction with a distractible titanium cage via an entirely posterior approach. Neurosurgery 2007; 60:223-30; discussion 230-1. [PMID: 17415157 DOI: 10.1227/01.neu.0000255385.18335.a8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE Surgical correction of thoracic kyphotic deformity is often associated with significant surgical and neurological morbidity and unsatisfactory reduction of kyphosis, especially in patients who cannot tolerate anterior thoracic procedures because of associated comorbidity. We describe a technique in which kyphotic deformity of the thoracic and thoracolumbar spine is corrected, decompressed, and stabilized with a circumferential fixation construct from a lone posterior approach. METHODS We reviewed the radiographic and clinical outcomes of seven patients undergoing vertebrectomy via a bilateral modified costotransversectomy approach followed by posterior placement of a distractible cage, reduction of the deformity via cage distraction, and supplemental dorsal instrumentation. All patients possessed thoracic/thoracolumbar kyphosis; however, a transthoracic approach was thought to be high risk because of medical comorbidity. RESULTS Seven patients underwent this procedure for thoracolumbar kyphosis resulting from a spinal tumor, osteomyelitis, and fracture. Vertebrectomies were performed at T2-T3, T4-T5, T5-T6, T12-L1, and L1. The mean preoperative kyphosis was 28.6 degrees, the mean postoperative kyphosis at the time of the final follow-up examination was 12.1 degrees, and the mean change in kyphosis was 53%. The mean long-term follow-up period was approximately 16 months. At the time of the final follow-up examination for all patients, there was no decline in neurological function, and pain management consisted of minimal use of oral narcotics. CONCLUSION This technique allows for circumferential decompression of the spinal cord via a posterior approach in patients with thoracic kyphotic deformities who cannot tolerate anterior thoracic approaches. In addition, in situ distraction of the expandable cage allows correction of sagittal imbalance and restores height without the potential loss of spinal height associated with osteotomies.
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Affiliation(s)
- Daniel M Sciubba
- Department of Neurological Surgery, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA.
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18
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Higgins KB, Sindall DR, Cuitino AM, Langrana NA. Biomechanical Alterations in Intact Osteoporotic Spine Due to Synthetic Augmentation: Finite Element Investigation. J Biomech Eng 2006; 129:575-85. [PMID: 17655479 DOI: 10.1115/1.2746379] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A three-dimensional nonlinear finite element model (FEM) was developed for a parametric study that examined the effect of synthetic augmentation on nonfractured vertebrae. The objective was to isolate those parameters primarily responsible for the effectiveness of the procedure; bone cement volume and bone density were expected to be highly important. Injection of bone cement was simulated in the FEM of a vertebral body that included a cellular model for the trabecular core. The addition of 10% and 20% cement by volume resulted in an increase in failure load, and the larger volume resulted in an increase in stiffness for the vertebral body. Placement of cement within the vertebral body was not as critical a parameter as cement amount. Simulated models of very poor bone quality saw the best therapeutic benefits.
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Affiliation(s)
- Kathryn B Higgins
- Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, NJ 08854, USA.
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19
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Si-Hoe KM, Teoh SH, Teo J. Radio-Translucent 3-Axis Mechanical Testing Rig for the Spine in Micro-CT. J Biomech Eng 2006; 128:957-64. [PMID: 17154698 DOI: 10.1115/1.2375136] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
To date, no apparatus has yet been devised which would allow the study of bone microstructure of the whole vertebrae under mechanical loading. This paper outlines the design and development of a 3-axis radio-translucent mechanical testing rig for spinal research and testing. This rig is to be used in conjunction with a Shimadzu micro-CT scanner. Several tests were conducted to verify the feasibility of the rig design. First, the maximum range of deformation in compression, flexion\extension, and lateral bending that could be exerted on a goat lumbar functional spinal unit was evaluated using the noncontact digital markers method. Stepwise compression loading was also conducted on a single porcine vertebra and the loading data was compared to results obtained from an industrial grade compression testing machine. Finally, micro-CT scans of a porcine vertebra prior to and at a compression failure strain were obtained. The rig was confirmed to be able to exert pure moment loading in the above mentioned modes of deformation and the extent of deformation was comparable to previous documented results. The stepwise compression loading conducted in the rig was also found to effectively approximate a continuous loading of the same specimen in an industrial grade compression testing machine. Finally, resultant micro-CT images of isotropic resolution 32.80μm of a porcine vertebra loaded in the rig were obtained. For the first time, trabecular microarchitecture detail of a whole vertebra buckling under 12.1% failure compression strain loading was studied using voxel-data visualization software. These initial series of tests verify the feasibility of the rig as an apparatus incorporating spinal testing and imaging.
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20
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Toh E, Yerby SA, Bay BK, McLain RF, Mochida J. The influence of pedicle screw placement on thoracic trabecular strain. Spinal Cord 2005; 44:249-53. [PMID: 16151448 DOI: 10.1038/sj.sc.3101830] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
STUDY DESIGN Experimental study. INTRODUCTION Although pedicle screw loosening and fracture are not uncommon, there is little understanding of the loading relationship between the pedicle screw and surrounding bone. There is even less understanding of the trabecular bone mechanics one a pedicle screw has been removed. OBJECTIVES To investigate and understand the influence of the presence of pedicle screw placement and subsequent removal on vertebral trabecular strain under axial loading. SETTING Orthopaedic Research Laboratories, University of California, Davis, USA. METHODS Six cadaver spines were biomechanically loaded and the minimum principal and maximum shear strains were measured using texture correlation. The treatments were divided into three conditions as follows: (1) before screw placement, (2) during screw placement, and (3) after screw removal. The obtained data were statistically analyzed. RESULTS Trabecular strain adjacent to the pedicle screw was increased following pedicle screw placement and remained high following pedicle screw removal. CONCLUSIONS The current study demonstrates that pedicle screw placement greatly influences the trabecular bone and introduces weakness in the area following screw removal.
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Affiliation(s)
- E Toh
- Department of Orthopaedic Surgery, Surgical Science, Tokai University School of Medicine, Isehara, Kanagawa, Japan
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21
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Nuckley DJ, Eck MP, Carter JW, Ching RP. Spinal maturation affects vertebral compressive mechanics and vBMD with sex dependence. Bone 2004; 35:720-8. [PMID: 15336609 DOI: 10.1016/j.bone.2004.04.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2003] [Revised: 04/12/2004] [Accepted: 04/15/2004] [Indexed: 11/30/2022]
Abstract
The effects of natural aging on the mechanics of the spine are far better understood for the mature adult spine than for the developing (immature) spine. Throughout its chondrification and ossification, the vertebra, which is the primary structural unit of the spine, undergoes enormous cellular, biochemical, and structural changes that should strongly influence its biomechanical response to external forces. Unfortunately, very little data exist for the mechanics of immature vertebrae. Vertebral maturation was therefore investigated in 22 baboon thoracic specimens to elucidate its relationship with biomechanics and volumetric bone mineral density (vBMD). Cadaveric baboon vertebrae were used due to the limited availability of human tissues in the pediatric age range. The specimen ages ranged between 1 and 30 human-equivalent years based on skeletal maturity. Isolated ninth thoracic vertebrae (T9) were subjected to compressive loading to document their compressive mechanical properties (yield load, stiffness, yield strength, and elastic modulus) and ashed to determine their volumetric bone mineral density. Spinal maturation was discovered to significantly increase vBMD (P < 0.0001) and compressive mechanics (stiffness, bulk elastic modulus, failure load, and bulk strength, P < 0.001) in a sex-dependent manner. Vertebral stiffness increased from 1218 N/mm at 1 year to 3534 N/mm at 30 years with a second order polynomial "maturation" relationship. Volumetric bone mineral density and vertebral cross-sectional area together described the developmental patterns of stiffness and yield load of isolated vertebrae. Sex differences were observed throughout development, demonstrating differing growth patterns to accommodate mechanical loading whereby males develop larger size vertebrae and females achieve their mechanical stiffness and strength through greater bone mineral density.
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Affiliation(s)
- David J Nuckley
- Applied Biomechanics Laboratory, Department of Mechanical Engineering, University of Washington, Seattle, WA 98109, USA.
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22
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McKinley TO, Bay BK. Trabecular bone strain changes associated with subchondral stiffening of the proximal tibia. J Biomech 2003; 36:155-63. [PMID: 12547352 DOI: 10.1016/s0021-9290(02)00386-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Subchondral stiffening is a hallmark pathologic feature of osteoarthritis but its mechanical and temporal relationship to the initiation or the progression of osteoarthritis is not established. The mechanical effect of subchondral stiffening on the surrounding trabecular bone is poorly understood. This study employs a relatively new application of digital image correlation to measure strain in the trabecular region of the proximal medial tibia in normal specimens and in specimens with simulated subchondral bone stiffening. Coronal sections from eight normal human cadaveric proximal tibiae were loaded in static compression and high resolution contact radiographs were made. Repeat contact radiographs were collected after the subchondral bone near the jointline was stiffened using polymethylmethacrylate. Digital images, made from loaded and unloaded contact radiographs, were compared using in-house software to measure trabecular displacement and calculate trabecular bone strain. Overall strain was higher in the stiffened specimens suggesting experimental artifiact significantly affected our results. Consistent increases in median maximum shear strain, median maximum principal strain, median minimum principal strain, and peak shear strain were measured near the inner and outer edges of the stiffened segment. Our experiment provides direct experimental measurement of increases in trabecular bone strain caused by subchondral stiffening, however, the clinical and biologic importance of strain increases is unknown.
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Affiliation(s)
- Todd O McKinley
- Department of Orthopaedic Surgery, University of Iowa Health Care, 200 Hawkins Drive 1020 JPP, Iowa City, IA 52242, USA.
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23
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Harrison DE, Jones EW, Janik TJ, Harrison DD. Evaluation of axial and flexural stresses in the vertebral body cortex and trabecular bone in lordosis and two sagittal cervical translation configurations with an elliptical shell model. J Manipulative Physiol Ther 2002; 25:391-401. [PMID: 12183697 DOI: 10.1067/mmt.2002.126128] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
BACKGROUND Osteoarthritis and spinal degeneration are factors in neck and back pain. Calculations of stress in clinically occurring configurations of the sagittal cervical spine are rare. OBJECTIVE To calculate and compare combined axial and flexural stresses in lordosis versus cervical configurations in anterior and vertical sagittal head translated positions. DESIGN Digitized measurements from lateral cervical radiographs of 3 different shapes were used to calculate axial loads and bending moments on the vertebral bodies of C2-C7. METHODS An elliptical shell model was used to model horizontal cross-sections of the vertebral bodies of C2 through T1. Axial and flexural stresses were calculated with short compression block equations. Elliptical shell modeling permitted separation of stresses into cortical and inner medullary regions. Digitized radiographic points were used to create polynomials representing the shape of the sagittal cervical curvatures from C1 to T1. To calculate bending moments at each vertebral segment, moment arms from a vertical line through C1 were determined from digitizing. RESULTS Compared with the normal lordosis, stresses on the anterior vertebral body cortical margins of C5-T1 in the sagittal translated postures are compression rather than tension. At the posterior vertebral bodies in the anteriorly translated position and vertically translated postures, the stresses change from compression to tension at C5 through T1. In absolute value (ABS) compared with values at the same segments in a normal lordosis, the magnitude of the combined anterior stresses in the sagittal postures are higher at C5-C7 (eg, ABS[sigma(straight)/sigma(normal)] approximately 1.25 to 4.25). CONCLUSIONS Vertebral body stresses are reversed in direction at C5-T1 in sagittal translated postures compared to a normal lordosis. Stress analysis, with implications for bone remodeling, indicates that both sagittal head translation postures, anterior head carriage, and vertical head translation, are undesirable configurations in the cervical spine.
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Affiliation(s)
- Deed E Harrison
- Department of Mechanical Engineering, Mississippi State University, Starkville, USA
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Toh E, Yerby SA, Bay BK, McLain RF, Benson DR, Mochida J. The effect of anterior osteophytes and flexural position on thoracic trabecular strain. Spine (Phila Pa 1976) 2001; 26:22-6. [PMID: 11148641 DOI: 10.1097/00007632-200101010-00006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Compressive and shear trabecular strains were evaluated using six cadaveric thoracic spines that included anterior osteophytes. The treatments were divided into three groups: 1) osteophytes intact and the specimen in the neutral position, 2) osteophytes removed and the specimen in the neutral position, and 3) osteophytes removed and the specimen with 5 degrees of additional flexion. OBJECTIVES To investigate the influence of osteophytes and flexural position on vertebral trabecular strain during axial compression. SUMMARY OF BACKGROUND DATA In the thoracic spine, the incidence of anterior wedge fractures increases with the severity of kyphosis. It is unclear whether the role of anterior osteophytes in the thoracic spine is to restrict progressive kyphosis, conduct axial load anteriorly, or both. METHODS Thoracic motion segments, T10-T12, were axially loaded in compression, and the minimum principal and maximum shear strains were measured using texture correlation. RESULTS No dramatic changes were found in the spatial distribution of the strains following removal of the anterior osteophytes. Conversely, after removal of the osteophytes and orienting the specimen in 5 degrees of additional flexion, the strain distribution shifted anteriorly and the magnitude increased. CONCLUSIONS This study demonstrated that osteophytes seem to restrict progressive kyphosis rather than conduct axial load anteriorly.
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Affiliation(s)
- E Toh
- Department of Orthopaedic Surgery, Tokai University School of Medicine, Kangawa, Japan.
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