After total hip arthroplasty, the stress shielding effect can occur due to the difference of stiffness between the metallic alloy of the stems and the host bone, which may cause a proximal bone loss. To overcome this problem, a low-modulus metastable β Ti-20Zr-3Mo-3Sn alloy composition has recently been designed to be potentially used for the cementless femoral hip stems. After having verified experimentally that the β alloy has a low modulus of around 50 GPa, a finite element analysis was performed on a Ti-20Zr-3Mo-3Sn alloy hip prosthesis model to evaluate the influence of a reduced modulus on stress shielding and stress fields in both stem and bone compared with the medical grade Ti-6Al-4V alloy whose elastic modulus reached 110 GPa. Our results show that the Ti-20Zr-3Mo-3Sn stem with low elastic modulus can effectively reduce the total stress shielding by 45.5% compared to the common Ti-6Al-4V prosthesis. Moreover, it is highlighted that the material elasticity affects the stress distribution in the implant, especially near the bone-stem interfaces.
{"title":"Finite element analysis of a low modulus Ti-20Zr-3Mo-3Sn alloy designed to reduce the stress shielding effect of a hip prosthesis","authors":"Tianyu Jia , Dominique Guines , Doina-Margareta Gordin , Lionel Leotoing , Thierry Gloriant","doi":"10.1016/j.jmbbm.2024.106640","DOIUrl":"10.1016/j.jmbbm.2024.106640","url":null,"abstract":"<div><p>After total hip arthroplasty, the stress shielding effect can occur due to the difference of stiffness between the metallic alloy of the stems and the host bone, which may cause a proximal bone loss. To overcome this problem, a low-modulus metastable β Ti-20Zr-3Mo-3Sn alloy composition has recently been designed to be potentially used for the cementless femoral hip stems. After having verified experimentally that the β alloy has a low modulus of around 50 GPa, a finite element analysis was performed on a Ti-20Zr-3Mo-3Sn alloy hip prosthesis model to evaluate the influence of a reduced modulus on stress shielding and stress fields in both stem and bone compared with the medical grade Ti-6Al-4V alloy whose elastic modulus reached 110 GPa. Our results show that the Ti-20Zr-3Mo-3Sn stem with low elastic modulus can effectively reduce the total stress shielding by 45.5% compared to the common Ti-6Al-4V prosthesis. Moreover, it is highlighted that the material elasticity affects the stress distribution in the implant, especially near the bone-stem interfaces.</p></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141452536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-19DOI: 10.1016/j.jmbbm.2024.106633
N.L. Church, A. Prasad, N.G. Jones
Developing new low modulus structures is important for reducing the risk of aseptic loosening during loading of implant materials. However, an alloy that may also confer some advantage at preventing septic loosening could dramatically improve the outcomes for patients. Nevertheless, the predictive power of current models remains limited to common alloying additions. As such, this study considers the mechanical properties of a range of Ti–Nb–Au superelastic alloys to elucidate the composition range for which low modulus structures can be achieved. These modulus values are compared to other critical design parameters such as strain recovery and strength. It was found that Au additions are effective at suppressing the formation of the ω phase and allow alloys with lower moduli to be achieved. It was also shown that low β phase stability is critical for achieving the lowest modulus, and that this susceptibility to transform to a martensite may enable higher strengths to be achieved. However, this low β phase stability also limits the strain recovery that may be achieved meaning these two properties are not necessarily independently tuneable. These data provide important context for the design of new systems containing unusual alloying additions such as Au.
{"title":"On the design of low modulus Ti–Nb–Au alloys for biomedical applications","authors":"N.L. Church, A. Prasad, N.G. Jones","doi":"10.1016/j.jmbbm.2024.106633","DOIUrl":"10.1016/j.jmbbm.2024.106633","url":null,"abstract":"<div><p>Developing new low modulus structures is important for reducing the risk of aseptic loosening during loading of implant materials. However, an alloy that may also confer some advantage at preventing septic loosening could dramatically improve the outcomes for patients. Nevertheless, the predictive power of current models remains limited to common alloying additions. As such, this study considers the mechanical properties of a range of Ti–Nb–Au superelastic alloys to elucidate the composition range for which low modulus structures can be achieved. These modulus values are compared to other critical design parameters such as strain recovery and strength. It was found that Au additions are effective at suppressing the formation of the ω phase and allow alloys with lower moduli to be achieved. It was also shown that low β phase stability is critical for achieving the lowest modulus, and that this susceptibility to transform to a martensite may enable higher strengths to be achieved. However, this low β phase stability also limits the strain recovery that may be achieved meaning these two properties are not necessarily independently tuneable. These data provide important context for the design of new systems containing unusual alloying additions such as Au.</p></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1751616124002650/pdfft?md5=9af98c40c9dc96fccc875ae25db72a97&pid=1-s2.0-S1751616124002650-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141474054","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Superficial fascia is a fibrofatty tissue found throughout the body. Initially described in relation to hernias, it has only recently received attention from the scientific community due to new evidence on its role in force transmission and structural integrity of the body. Considering initial difficulties in its anatomical identification, to date, a characterization of the superficial fascia through mechanical tests is still lacking.
The mechanical properties of human superficial fasciae of abdominal and thoracic districts (back) of different subjects (n = 4) were then investigated, focusing on anisotropy and viscoelasticity. Experimental tests were performed on samples taken in two perpendicular directions according to body planes (cranio-caudal and latero-medial axes). Data collected from two different uniaxial tensile protocols, failure (i.e., ultimate tensile strength and strain at break, Young's modulus and toughness) and stress-relaxation (i.e., residual stress), were processed and then grouped for statistical analysis.
Failure tests confirmed tissue anisotropy, revealing the stiffer nature of the latero-medial direction compared to the cranio-caudal one, for both the districts (with a ratio of the respective Young's moduli close to 2). Furthermore, the thoracic region exhibited significantly greater strength and resultant Young's modulus compared to the abdomen (with greater results along the latero-medial direction, such as 6.13 ± 3.11 MPa versus 0.85 ± 0.39 MPa and 24.87 ± 15.23 MPa versus 3.19 ± 1.62 MPa, respectively). On the contrary, both regions displayed similar strain at break (varying between 38 and 47%), with no clear dependence from the loading directions. Stress-relaxation tests highlighted the viscous behavior of the superficial fascia, with no significant differences in the stress decay between directions and districts (35–38% of residual stress after 300 s).
All these collected results represent the starting point for a more in-depth knowledge of the mechanical characterization of the superficial fascia, which can have direct implications in the design, implementation, and effectiveness of site-specific treatments.
{"title":"Biomechanical properties of the human superficial fascia: Site-specific variability and anisotropy of abdominal and thoracic regions","authors":"Alice Berardo , Lorenza Bonaldi , Carla Stecco , Chiara Giulia Fontanella","doi":"10.1016/j.jmbbm.2024.106637","DOIUrl":"https://doi.org/10.1016/j.jmbbm.2024.106637","url":null,"abstract":"<div><p>Superficial fascia is a fibrofatty tissue found throughout the body. Initially described in relation to hernias, it has only recently received attention from the scientific community due to new evidence on its role in force transmission and structural integrity of the body. Considering initial difficulties in its anatomical identification, to date, a characterization of the superficial fascia through mechanical tests is still lacking.</p><p>The mechanical properties of human superficial fasciae of abdominal and thoracic districts (back) of different subjects (n = 4) were then investigated, focusing on anisotropy and viscoelasticity. Experimental tests were performed on samples taken in two perpendicular directions according to body planes (cranio-caudal and latero-medial axes). Data collected from two different uniaxial tensile protocols, failure (i.e., ultimate tensile strength and strain at break, Young's modulus and toughness) and stress-relaxation (i.e., residual stress), were processed and then grouped for statistical analysis.</p><p>Failure tests confirmed tissue anisotropy, revealing the stiffer nature of the latero-medial direction compared to the cranio-caudal one, for both the districts (with a ratio of the respective Young's moduli close to 2). Furthermore, the thoracic region exhibited significantly greater strength and resultant Young's modulus compared to the abdomen (with greater results along the latero-medial direction, such as 6.13 ± 3.11 MPa versus 0.85 ± 0.39 MPa and 24.87 ± 15.23 MPa versus 3.19 ± 1.62 MPa, respectively). On the contrary, both regions displayed similar strain at break (varying between 38 and 47%), with no clear dependence from the loading directions. Stress-relaxation tests highlighted the viscous behavior of the superficial fascia, with no significant differences in the stress decay between directions and districts (35–38% of residual stress after 300 s).</p><p>All these collected results represent the starting point for a more in-depth knowledge of the mechanical characterization of the superficial fascia, which can have direct implications in the design, implementation, and effectiveness of site-specific treatments.</p></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1751616124002698/pdfft?md5=ebc207d6b758f9ef0990003f39875bde&pid=1-s2.0-S1751616124002698-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141444626","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-18DOI: 10.1016/j.jmbbm.2024.106635
Philipp Winnand, Ezgi Cevik, Mark Ooms, Marius Heitzer, Anna Bock, Frank Hölzle, Ali Modabber, Stefan Raith
Background
Surgical correction of unicoronal craniosynostosis (UCS) is highly complex due to its asymmetric appearance. Although fronto-orbital advancement (FOA) is a versatile technique for craniosynostosis correction, harmonization of the orbital bandeau in UCS is difficult to predict. This study evaluates the biomechanics of the orbital bandeau using different patterns and varying characteristics of inner cortical bone layer osteotomies in a finite element (FE) analysis.
Method
An FE model was created using the computed tomography (CT) scan of a 6.5-month-old male infant with a right-sided UCS. The unaffected side of the orbital bandeau was virtually mirrored, and anatomical correction of the orbital bandeau was simulated. Different combinations of osteotomy patterns, numbers, depths, and widths were examined (n = 48) and compared to an uncut model.
Results
Reaction forces and maximum stress values differed significantly (p < 0.01) among osteotomy patterns and between each osteotomy characteristic. Regardless of the osteotomy pattern, higher numbers of osteotomies significantly (p < 0.05) correlated with reductions in reaction force and maximum stress. An X-shaped configuration with three osteotomies deep and wide to the bone was biomechanically the most favorable model.
Conclusion
Inner cortical bone layer osteotomy might be an effective modification to the conventional FOA approach in terms of predictable shaping of the orbital bandeau.
{"title":"Optimal untwisting of the orbital bandeau in unicoronal craniosynostosis correction: A finite element analysis","authors":"Philipp Winnand, Ezgi Cevik, Mark Ooms, Marius Heitzer, Anna Bock, Frank Hölzle, Ali Modabber, Stefan Raith","doi":"10.1016/j.jmbbm.2024.106635","DOIUrl":"10.1016/j.jmbbm.2024.106635","url":null,"abstract":"<div><h3>Background</h3><p>Surgical correction of unicoronal craniosynostosis (UCS) is highly complex due to its asymmetric appearance. Although fronto-orbital advancement (FOA) is a versatile technique for craniosynostosis correction, harmonization of the orbital bandeau in UCS is difficult to predict. This study evaluates the biomechanics of the orbital bandeau using different patterns and varying characteristics of inner cortical bone layer osteotomies in a finite element (FE) analysis.</p></div><div><h3>Method</h3><p>An FE model was created using the computed tomography (CT) scan of a 6.5-month-old male infant with a right-sided UCS. The unaffected side of the orbital bandeau was virtually mirrored, and anatomical correction of the orbital bandeau was simulated. Different combinations of osteotomy patterns, numbers, depths, and widths were examined (n = 48) and compared to an uncut model.</p></div><div><h3>Results</h3><p>Reaction forces and maximum stress values differed significantly (<em>p</em> < 0.01) among osteotomy patterns and between each osteotomy characteristic. Regardless of the osteotomy pattern, higher numbers of osteotomies significantly (<em>p</em> < 0.05) correlated with reductions in reaction force and maximum stress. An X-shaped configuration with three osteotomies deep and wide to the bone was biomechanically the most favorable model.</p></div><div><h3>Conclusion</h3><p>Inner cortical bone layer osteotomy might be an effective modification to the conventional FOA approach in terms of predictable shaping of the orbital bandeau.</p></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1751616124002674/pdfft?md5=707e5871177093387ad07c3e6ccd78ca&pid=1-s2.0-S1751616124002674-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141474055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-18DOI: 10.1016/j.jmbbm.2024.106636
Harish Palnitkar , Rolf Reiter , Shreyan Majumdar , Joseph Crutison , Shujun Lin , Thomas J. Royston , Dieter Klatt
Background
Despite its success in the mechanical characterization of biological tissues, magnetic resonance elastography (MRE) uses ill-posed wave inversions to estimate tissue stiffness. 1-Norm has been recently introduced as a mathematical measure for the scattering of mechanical waves due to inhomogeneities based on an analysis of the delineated contours of wave displacement.
Purpose
To investigate 1-Norm as an MRE-based quantitative biomarker of mechanical inhomogeneities arising from microscopic structural tissue alterations caused by the freeze-thaw cycle (FTC) or Alzheimer's disease (AD).
Methods
In this proof-of-concept study, we prospectively investigated excised porcine kidney (n = 6), liver (n = 6), and muscle (n = 6) before vs. after the FTC at 500–2000 Hz and excised murine brain of healthy controls (n = 3) vs. 5xFAD species with AD (n = 3) at 1200–1800 Hz using 0.5 T tabletop MRE. 1-Norm analysis was compared with conventional wave inversion.
Results
While the FTC reduced both stiffness and inhomogeneity in kidney, liver, and muscle tissue, AD led to lower brain stiffness but more pronounced mechanical inhomogeneity.
Conclusion
Our preliminary results show that 1-Norm is sensitive to tissue mechanical inhomogeneity due to FTC and AD without relying on ill-posed wave inversion techniques. 1-Norm has the potential to be used as an MRE-based diagnostic biomarker independent of stiffness to characterize abnormal conditions that involve changes in tissue mechanical inhomogeneity.
{"title":"1-Norm waveform analysis for MR elastography-based quantification of inhomogeneity: Effects of the freeze-thaw cycle and Alzheimer's disease","authors":"Harish Palnitkar , Rolf Reiter , Shreyan Majumdar , Joseph Crutison , Shujun Lin , Thomas J. Royston , Dieter Klatt","doi":"10.1016/j.jmbbm.2024.106636","DOIUrl":"https://doi.org/10.1016/j.jmbbm.2024.106636","url":null,"abstract":"<div><h3>Background</h3><p>Despite its success in the mechanical characterization of biological tissues, magnetic resonance elastography (MRE) uses ill-posed wave inversions to estimate tissue stiffness. 1-Norm has been recently introduced as a mathematical measure for the scattering of mechanical waves due to inhomogeneities based on an analysis of the delineated contours of wave displacement.</p></div><div><h3>Purpose</h3><p>To investigate 1-Norm as an MRE-based quantitative biomarker of mechanical inhomogeneities arising from microscopic structural tissue alterations caused by the freeze-thaw cycle (FTC) or Alzheimer's disease (AD).</p></div><div><h3>Methods</h3><p>In this proof-of-concept study, we prospectively investigated excised porcine kidney (<em>n</em> = 6), liver (<em>n</em> = 6), and muscle (<em>n</em> = 6) before vs. after the FTC at 500–2000 Hz and excised murine brain of healthy controls (<em>n</em> = 3) vs. 5xFAD species with AD (<em>n</em> = 3) at 1200–1800 Hz using 0.5 T tabletop MRE. 1-Norm analysis was compared with conventional wave inversion.</p></div><div><h3>Results</h3><p>While the FTC reduced both stiffness and inhomogeneity in kidney, liver, and muscle tissue, AD led to lower brain stiffness but more pronounced mechanical inhomogeneity.</p></div><div><h3>Conclusion</h3><p>Our preliminary results show that 1-Norm is sensitive to tissue mechanical inhomogeneity due to FTC and AD without relying on ill-posed wave inversion techniques. 1-Norm has the potential to be used as an MRE-based diagnostic biomarker independent of stiffness to characterize abnormal conditions that involve changes in tissue mechanical inhomogeneity.</p></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1751616124002686/pdfft?md5=47a2a48c69f7ce95b3c19f4720821a85&pid=1-s2.0-S1751616124002686-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141438891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-17DOI: 10.1016/j.jmbbm.2024.106630
Elisa Roldán , Neil D. Reeves , Glen Cooper , Kirstie Andrews
Currently, the use of autografts is the gold standard for the replacement of many damaged biological tissues. However, this practice presents disadvantages that can be mitigated through tissue-engineered implants. The aim of this study is to explore how machine learning can mechanically evaluate 2D and 3D polyvinyl alcohol (PVA) electrospun scaffolds (one twisted filament, 3 twisted filament and 3 twisted/braided filament scaffolds) for their use in different tissue engineering applications. Crosslinked and non-crosslinked scaffolds were fabricated and mechanically characterised, in dry/wet conditions and under longitudinal/transverse loading, using tensile testing. 28 machine learning models (ML) were used to predict the mechanical properties of the scaffolds. 4 exogenous variables (structure, environmental condition, crosslinking and direction of the load) were used to predict 2 endogenous variables (Young’s modulus and ultimate tensile strength). ML models were able to identify 6 structures and testing conditions with comparable Young’s modulus and ultimate tensile strength to ligamentous tissue, skin tissue, oral and nasal tissue, and renal tissue. This novel study proved that Classification and Regression Trees (CART) models were an innovative and easy to interpret tool to identify biomimetic electrospun structures; however, Cubist and Support Vector Machine (SVM) models were the most accurate, with R2 of 0.93 and 0.8, to predict the ultimate tensile strength and Young’s modulus, respectively. This approach can be implemented to optimise the manufacturing process in different applications.
{"title":"Machine learning to mechanically assess 2D and 3D biomimetic electrospun scaffolds for tissue engineering applications: Between the predictability and the interpretability","authors":"Elisa Roldán , Neil D. Reeves , Glen Cooper , Kirstie Andrews","doi":"10.1016/j.jmbbm.2024.106630","DOIUrl":"https://doi.org/10.1016/j.jmbbm.2024.106630","url":null,"abstract":"<div><p>Currently, the use of autografts is the gold standard for the replacement of many damaged biological tissues. However, this practice presents disadvantages that can be mitigated through tissue-engineered implants. The aim of this study is to explore how machine learning can mechanically evaluate 2D and 3D polyvinyl alcohol (PVA) electrospun scaffolds (one twisted filament, 3 twisted filament and 3 twisted/braided filament scaffolds) for their use in different tissue engineering applications. Crosslinked and non-crosslinked scaffolds were fabricated and mechanically characterised, in dry/wet conditions and under longitudinal/transverse loading, using tensile testing. 28 machine learning models (ML) were used to predict the mechanical properties of the scaffolds. 4 exogenous variables (structure, environmental condition, crosslinking and direction of the load) were used to predict 2 endogenous variables (Young’s modulus and ultimate tensile strength). ML models were able to identify 6 structures and testing conditions with comparable Young’s modulus and ultimate tensile strength to ligamentous tissue, skin tissue, oral and nasal tissue, and renal tissue. This novel study proved that Classification and Regression Trees (<span>CART</span>) models were an innovative and easy to interpret tool to identify biomimetic electrospun structures; however, Cubist and Support Vector Machine (SVM) models were the most accurate, with R<sup>2</sup> of 0.93 and 0.8, to predict the ultimate tensile strength and Young’s modulus, respectively. This approach can be implemented to optimise the manufacturing process in different applications.</p></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1751616124002625/pdfft?md5=4c476074ad7a93e943c8ab5c3bf4a9ad&pid=1-s2.0-S1751616124002625-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141423501","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-14DOI: 10.1016/j.jmbbm.2024.106625
Daniel Yoon , Kevin N. Eckstein , Margrethe Ruding , Philip V. Bayly
We investigated the ability to tune the anisotropic mechanical properties of 3D-printed hydrogel lattices by modifying their geometry (lattice strut diameter, unit cell size, and unit cell scaling factor). Many soft tissues are anisotropic and the ability to mimic natural anisotropy would be valuable for developing tissue-surrogate “phantoms” for elasticity imaging (shear wave elastography or magnetic resonance elastography). Vintile lattices were 3D-printed in polyethylene glycol di-acrylate (PEGDA) using digital light projection printing. Two mechanical benchtop tests, dynamic shear testing and unconfined compression, were used to measure the apparent shear storage moduli (G′) and apparent Young's moduli (E) of lattice samples. Increasing the unit cell size from 1.25 mm to 2.00 mm reduced the Young's and shear moduli of the lattices by 91% and 85%, respectively. Decreasing the strut diameter from 300 μm to 200 μm reduced the apparent shear moduli of the lattices by 95%. Increasing the geometric scaling ratio of the lattice unit cells from 1.00 × to 2.00 × increased mechanical anisotropy in shear (by a factor of 3.1) and in compression (by a factor of 2.9). Both simulations and experiments show that the effects of unit cell size and strut diameter are consistent with power law relationships between volume fraction and apparent elastic moduli. In particular, experimental measurements of apparent Young's moduli agree well with predictions of the theoretical Gibson-Ashby model. Thus, the anisotropic mechanical properties of a lattice can be tuned by the unit cell size, the strut diameter, and scaling factors. This approach will be valuable in designing tissue-mimicking hydrogel lattice-based composite materials for elastography phantoms and tissue engineered scaffolds.
{"title":"Structural tuning of anisotropic mechanical properties in 3D-Printed hydrogel lattices","authors":"Daniel Yoon , Kevin N. Eckstein , Margrethe Ruding , Philip V. Bayly","doi":"10.1016/j.jmbbm.2024.106625","DOIUrl":"10.1016/j.jmbbm.2024.106625","url":null,"abstract":"<div><p>We investigated the ability to tune the anisotropic mechanical properties of 3D-printed hydrogel lattices by modifying their geometry (lattice strut diameter, unit cell size, and unit cell scaling factor). Many soft tissues are anisotropic and the ability to mimic natural anisotropy would be valuable for developing tissue-surrogate “phantoms” for elasticity imaging (shear wave elastography or magnetic resonance elastography). Vintile lattices were 3D-printed in polyethylene glycol di-acrylate (PEGDA) using digital light projection printing. Two mechanical benchtop tests, dynamic shear testing and unconfined compression, were used to measure the apparent shear storage moduli (G′) and apparent Young's moduli (E) of lattice samples. Increasing the unit cell size from 1.25 mm to 2.00 mm reduced the Young's and shear moduli of the lattices by 91% and 85%, respectively. Decreasing the strut diameter from 300 μm to 200 μm reduced the apparent shear moduli of the lattices by 95%. Increasing the geometric scaling ratio of the lattice unit cells from 1.00 × to 2.00 × increased mechanical anisotropy in shear (by a factor of 3.1) and in compression (by a factor of 2.9). Both simulations and experiments show that the effects of unit cell size and strut diameter are consistent with power law relationships between volume fraction and apparent elastic moduli. In particular, experimental measurements of apparent Young's moduli agree well with predictions of the theoretical Gibson-Ashby model. Thus, the anisotropic mechanical properties of a lattice can be tuned by the unit cell size, the strut diameter, and scaling factors. This approach will be valuable in designing tissue-mimicking hydrogel lattice-based composite materials for elastography phantoms and tissue engineered scaffolds.</p></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141410637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-13DOI: 10.1016/j.jmbbm.2024.106631
Daniel R. Martel , Jack P. Callaghan , Marina Mourtzakis , Thomas L. Willett , Andrew C. Laing
Fall-related hip fractures are a serious public health issue in older adults. As most mechanistic hip fracture risk prediction models incorporate tissue tolerance, test methods that can accurately characterize the fracture force of the femur (and factors that influence it) are imperative. While bone possesses viscoelastic properties, experimental characterization of rate-dependencies has been inconsistent in the whole-femur literature. The goal of this study was to investigate the influence of experimental paradigm on loading rate and fracture force (both means and variability) during mechanical tests simulating lateral fall loadings on the proximal femur. Six pairs of matched femurs were split randomly between two test paradigms: a ‘lower rate’ materials testing system (MTS) with a constant displacement rate of 60 mm/s, and a hip impact test system (HIT) comprised of a custom-built vertical drop tower utilizing an impact velocity of 4 m/s. The loading rate was 88-fold higher for the HIT (mean (SD) = 2465.49 (807.38) kN/s) compared to the MTS (27.78 (10.03) kN/s) paradigm. However, no difference in fracture force was observed between test paradigms (mean (SD) = 4096.4 (1272.6) N for HIT, and 3641.3 (1285.8) N for MTS). Within-paradigm variability was not significantly different across paradigms for either loading rate or fracture force (coefficients of variation ranging from 0.311 to 0.361). Within each test paradigm, significant positive relationships were observed between loading rate and fracture force (HIT adjusted R2 = 0.833, p = 0.007; MTS adjusted R2 = 0.983, p < 0.0001). Overall, this study provides evidence that energy-based impact simulators can be a valid method to measure femoral bone strength in the context of fall-related hip fractures. This study motivates future research to characterize potential non-linear relationships between loading rate and fracture threshold at both macro and microscales.
{"title":"Influence of test paradigm on loading dynamics during proximal femur fracture tests simulating sideways falls","authors":"Daniel R. Martel , Jack P. Callaghan , Marina Mourtzakis , Thomas L. Willett , Andrew C. Laing","doi":"10.1016/j.jmbbm.2024.106631","DOIUrl":"10.1016/j.jmbbm.2024.106631","url":null,"abstract":"<div><p>Fall-related hip fractures are a serious public health issue in older adults. As most mechanistic hip fracture risk prediction models incorporate tissue tolerance, test methods that can accurately characterize the fracture force of the femur (and factors that influence it) are imperative. While bone possesses viscoelastic properties, experimental characterization of rate-dependencies has been inconsistent in the whole-femur literature. The goal of this study was to investigate the influence of experimental paradigm on loading rate and fracture force (both means and variability) during mechanical tests simulating lateral fall loadings on the proximal femur. Six pairs of matched femurs were split randomly between two test paradigms: a ‘lower rate’ materials testing system (MTS) with a constant displacement rate of 60 mm/s, and a hip impact test system (HIT) comprised of a custom-built vertical drop tower utilizing an impact velocity of 4 m/s. The loading rate was 88-fold higher for the HIT (mean (SD) = 2465.49 (807.38) kN/s) compared to the MTS (27.78 (10.03) kN/s) paradigm. However, no difference in fracture force was observed between test paradigms (mean (SD) = 4096.4 (1272.6) N for HIT, and 3641.3 (1285.8) N for MTS). Within-paradigm variability was not significantly different across paradigms for either loading rate or fracture force (coefficients of variation ranging from 0.311 to 0.361). Within each test paradigm, significant positive relationships were observed between loading rate and fracture force (HIT adjusted R<sup>2</sup> = 0.833, <em>p</em> = 0.007; MTS adjusted R<sup>2</sup> = 0.983, <em>p</em> < 0.0001). Overall, this study provides evidence that energy-based impact simulators can be a valid method to measure femoral bone strength in the context of fall-related hip fractures. This study motivates future research to characterize potential non-linear relationships between loading rate and fracture threshold at both macro and microscales.</p></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1751616124002637/pdfft?md5=1cfd47197d363bb832a7c250df646399&pid=1-s2.0-S1751616124002637-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141392690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-10DOI: 10.1016/j.jmbbm.2024.106628
Zhongwei Sun, Changwen Mi
This study addresses three primary objectives related to lumbar intervertebral disc (IVD) biomechanics under ramping quasi-static loading conditions. First, we explore the conditions justifying the simplification of axisymmetric elastic fiber families into single fiber bundles through discretized strain energy functions. Simulations reveal that a concentration factor exceeding 10 allows for a consistent deviation below 10% between simplified and non-simplified responses. Second, we investigate the impact of elastic fibers on the physiological stiffness in IVDs, revealing minimal influence on biological motions but significant effects on degeneration. Lastly, we examine the initiation and progression of annulus fibrosus (AF) damage. Our findings confirm the validity of simplifying elastic fiber families and underscore the necessity of considering elastic fiber damage in biomechanical studies of AF tissues. Elastic fibers contribute to increased biaxial stretch stiffness, and their damage significantly affects the loading capacity of the inner AF. Additionally, degeneration significantly alters the susceptibility to damage in the AF, with specific regions exhibiting higher vulnerability. Damage tends to extend circumferentially and radially, emphasizing the regional variations in collagen and elastic fiber properties. This study offers useful insights for refining biomechanical models, paving the way for a more comprehensive understanding of IVD responses and potential clinical implications.
本研究探讨了在斜坡准静态加载条件下腰椎间盘(IVD)生物力学的三个主要目标。首先,我们探讨了通过离散化应变能函数将轴对称弹性纤维族简化为单纤维束的合理条件。模拟结果表明,浓度系数超过 10 时,简化响应与非简化响应之间的偏差始终低于 10%。其次,我们研究了弹性纤维对 IVD 生理刚度的影响,发现弹性纤维对生物运动的影响微乎其微,但对退化的影响却很大。最后,我们研究了纤维环(AF)损伤的开始和发展。我们的研究结果证实了简化弹性纤维家族的有效性,并强调了在对纤维环组织进行生物力学研究时考虑弹性纤维损伤的必要性。弹性纤维有助于增加双轴拉伸刚度,其损伤会显著影响内部 AF 的负荷能力。此外,退行性变还会显著改变心房颤动的易损性,特定区域的易损性更高。损伤倾向于向圆周和径向延伸,强调了胶原蛋白和弹性纤维特性的区域性变化。这项研究为完善生物力学模型提供了有用的见解,为更全面地了解 IVD 反应和潜在的临床影响铺平了道路。
{"title":"Biomechanics of annulus fibrosus: Elastic fiber simplification and degenerative impact on damage initiation and propagation","authors":"Zhongwei Sun, Changwen Mi","doi":"10.1016/j.jmbbm.2024.106628","DOIUrl":"https://doi.org/10.1016/j.jmbbm.2024.106628","url":null,"abstract":"<div><p>This study addresses three primary objectives related to lumbar intervertebral disc (IVD) biomechanics under ramping quasi-static loading conditions. First, we explore the conditions justifying the simplification of axisymmetric elastic fiber families into single fiber bundles through discretized strain energy functions. Simulations reveal that a concentration factor exceeding 10 allows for a consistent deviation below 10% between simplified and non-simplified responses. Second, we investigate the impact of elastic fibers on the physiological stiffness in IVDs, revealing minimal influence on biological motions but significant effects on degeneration. Lastly, we examine the initiation and progression of annulus fibrosus (AF) damage. Our findings confirm the validity of simplifying elastic fiber families and underscore the necessity of considering elastic fiber damage in biomechanical studies of AF tissues. Elastic fibers contribute to increased biaxial stretch stiffness, and their damage significantly affects the loading capacity of the inner AF. Additionally, degeneration significantly alters the susceptibility to damage in the AF, with specific regions exhibiting higher vulnerability. Damage tends to extend circumferentially and radially, emphasizing the regional variations in collagen and elastic fiber properties. This study offers useful insights for refining biomechanical models, paving the way for a more comprehensive understanding of IVD responses and potential clinical implications.</p></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141324543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, the Ti6Al4V alloy surface was modified via ceramic conversion treatment (CCT) with or without a pre-deposited silver layer. After characterizing the surface morphologies, microstructure and phase constituents of the ceramic oxide layer formed at 620 °C, we investigated the surface hardness and the cross-sectional nano-hardness profile under the oxide layer. The static load-bearing capacity of the oxide layers was examined by applying discrete loads via a Vickers indenter and observing the indentations. A scratch test was used to evaluate the load-bearing capacity and the adhesion/cohesion of the oxide layers. The wettability of the surface changed due to the incorporation of silver and the change of surface morphology. Reciprocating friction and wear test was used to assess the tribological properties. Small and dispersed silver nanoparticles and clusters were found in the oxide layer of the Ag pre-deposited Ti6Al4V samples, and they had much better tribological properties in terms of reduced coefficient of friction and wear volume. With the assistance of silver, the efficiency of the CCT was significantly improved.
本文通过陶瓷转化处理(CCT)对 Ti6Al4V 合金表面进行了改性,无论是否有预沉积银层。在对 620 °C 下形成的陶瓷氧化层的表面形态、微观结构和相组成进行表征后,我们研究了氧化层下的表面硬度和横截面纳米硬度曲线。通过维氏压头施加离散载荷并观察压痕,检验了氧化层的静态承载能力。划痕试验用于评估氧化层的承载能力和附着力/粘合力。由于银的加入和表面形态的变化,表面的润湿性也发生了变化。往复摩擦和磨损测试用于评估摩擦学特性。在银预沉积 Ti6Al4V 样品的氧化层中发现了小而分散的银纳米颗粒和银簇,它们在降低摩擦系数和磨损体积方面具有更好的摩擦学特性。在银的帮助下,CCT 的效率显著提高。
{"title":"Silver-promoted ceramic conversion treatment of Ti6Al4V alloy and its mechanical performance","authors":"Zhenxue Zhang, Yuejiao Zhang, Peize Li, Andrew Burns, Xiaoying Li, Hanshan Dong","doi":"10.1016/j.jmbbm.2024.106629","DOIUrl":"10.1016/j.jmbbm.2024.106629","url":null,"abstract":"<div><p>In this paper, the Ti6Al4V alloy surface was modified via ceramic conversion treatment (CCT) with or without a pre-deposited silver layer. After characterizing the surface morphologies, microstructure and phase constituents of the ceramic oxide layer formed at 620 °C, we investigated the surface hardness and the cross-sectional nano-hardness profile under the oxide layer. The static load-bearing capacity of the oxide layers was examined by applying discrete loads via a Vickers indenter and observing the indentations. A scratch test was used to evaluate the load-bearing capacity and the adhesion/cohesion of the oxide layers. The wettability of the surface changed due to the incorporation of silver and the change of surface morphology. Reciprocating friction and wear test was used to assess the tribological properties. Small and dispersed silver nanoparticles and clusters were found in the oxide layer of the Ag pre-deposited Ti6Al4V samples, and they had much better tribological properties in terms of reduced coefficient of friction and wear volume. With the assistance of silver, the efficiency of the CCT was significantly improved.</p></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1751616124002613/pdfft?md5=f7e911ae1c83099aad882fd3882ea55e&pid=1-s2.0-S1751616124002613-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141415032","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}