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Pitre NN, Moses JB, Fisher M, Kuwabar Y, Salvatian S, Watkins SC, Tzeng E, Velankar SS. The morphology of internal elastic lamina corrugations in arteries under physiological conditions. Morphologie 2024; 108:100902. [PMID: 39180804 DOI: 10.1016/j.morpho.2024.100902] [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: 02/22/2024] [Revised: 07/26/2024] [Accepted: 07/31/2024] [Indexed: 08/27/2024]
Abstract
BACKGROUND In elastic and resistance arteries, an elastin-rich membrane, the Internal Elastic Lamina (IEL), separates the tunica intima from the underlying tunica media. The IEL often appears wrinkled or corrugated in histological images. These corrugations are sometimes ascribed to vessel contraction ex vivo, and to fixation artifacts, and therefore regarded as not physiologically relevant. We examine whether the IEL remains corrugated even under physiological conditions. METHODS The diameters of carotid arteries of anesthetized pigs were measured by ultrasound. The arteries were then excised, inflated within a conical sleeve, fixed, and imaged by confocal microscopy. The conical sleeve allows fixing each artery across a wide range of diameters, which bracket its ultrasound diameter. Thus the study was designed to quantify how corrugations change with diameter for a single artery, and test whether corrugations exist when the fixed artery matches the ultrasound diameter. RESULTS At diameters below the ultrasound diameter (i.e. when the artery was constricted as compared to ultrasound conditions), the IEL corrugations were found to decrease significantly with increasing diameter, but not fully flatten at the ultrasound diameter. The contour length of the IEL was found to be roughly 10% larger than the circumference of the artery measured by ultrasound. The physiological diameter is likely to be even smaller than the ultrasound diameter since ultrasound was conducted with the animal under general anesthesia, which leads to vasodilation, suggesting a higher level of corrugation under physiological conditions. For arterial cross sections constricted below the ultrasound diameter, the IEL contour length decreased roughly with the square root of the diameter. CONCLUSION The primary conclusions of this study are: a) the IEL is corrugated when the artery is constricted and flattens as the artery diameter increases; b) the IEL is corrugated under physiological conditions and has a contour length at least 10% more than the physiological arterial diameter; and c) the IEL despite being relatively stiffer than the surrounding arterial layers, does not behave like an inextensible membrane.
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Affiliation(s)
- N N Pitre
- Department of Bioengineering, University of Pittsburgh, 15261 Pittsburgh, PA, USA
| | - J B Moses
- Department of Surgery, University of Pittsburgh, 15261 Pittsburgh, PA, USA
| | - M Fisher
- Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh, 15261 Pittsburgh, PA, USA
| | - Y Kuwabar
- Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh, 15261 Pittsburgh, PA, USA
| | - S Salvatian
- Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh, 15261 Pittsburgh, PA, USA
| | - S C Watkins
- Department of Cell Biology, University of Pittsburgh, 15261 Pittsburgh, PA, USA
| | - E Tzeng
- Department of Surgery, University of Pittsburgh, 15261 Pittsburgh, PA, USA
| | - S S Velankar
- Department of Chemical Engineering, University of Pittsburgh, 15261 Pittsburgh, PA, USA; Department of Mechanical Engineering and Materials Science, University of Pittsburgh, 15261 Pittsburgh, PA, USA; McGowan Institute of Regenerative Medicine, University of Pittsburgh, 15261 Pittsburgh, PA, USA.
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Pagnanelli M, De Gaetano F, Callera A, Nappo G, Capretti G, Carrara S, Ferrari AMR, Cellesi F, Costantino ML, Zerbi A. Analysis of the Mechanical Characteristics of Human Pancreas through Indentation: Preliminary In Vitro Results on Surgical Samples. Biomedicines 2024; 12:91. [PMID: 38255197 PMCID: PMC10813168 DOI: 10.3390/biomedicines12010091] [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: 11/01/2023] [Revised: 12/15/2023] [Accepted: 12/27/2023] [Indexed: 01/24/2024] Open
Abstract
Pancreatic surgery is extremely challenging and demands an extended learning curve to be executed with a low incidence of post-operative complications. The soft consistency of the human pancreas poses a primary challenge for pancreatic surgeons. This study aimed to analyze the preliminary mechanical characteristics of the human pancreas to develop a realistic synthetic phantom for surgical simulations in the near future. Pancreatic specimens, comprehensive of the pancreatic parenchyma and main pancreatic duct, were collected during pancreatic resections and analyzed through nano-bio-indentation (BioindenterTM UNHT3 Bio, Anton Paar GmbH, Graz, Austria) to measure the elastic modulus. Comparisons were made between slow and fast loading rates, immediate and post-freezing analyses, and multipoint indentations. The results demonstrated that a slow loading rate (30 μN/min), immediate analysis, and multipoint measurements are crucial for obtaining accurate values of the elastic modulus of the human pancreas (1.40 ± 0.47 kPa). In particular, the study revealed that analysis after freezing could impact the outcomes of the indentation. Moreover, the study suggested that both the pancreatic parenchyma and the main pancreatic duct should be analyzed to achieve a more precise and comprehensive definition of the. mechanical features of the pancreas. These preliminary findings represent the initial steps toward defining the consistency and mechanical characteristics of human pancreatic tissue with the goal of creating a realistic synthetic phantom.
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Affiliation(s)
- Michele Pagnanelli
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, Pieve Emanuele, 20072 Milan, Italy; (G.N.); (G.C.); (A.Z.)
- Pancreatic Unit, IRCCS Humanitas Research Hospital, Via Manzoni 56, Rozzano, 20089 Milan, Italy; (F.D.G.); (A.C.)
| | - Francesco De Gaetano
- Pancreatic Unit, IRCCS Humanitas Research Hospital, Via Manzoni 56, Rozzano, 20089 Milan, Italy; (F.D.G.); (A.C.)
- Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, 20133 Milano, Italy; (A.M.R.F.); (F.C.); (M.L.C.)
| | - Arianna Callera
- Pancreatic Unit, IRCCS Humanitas Research Hospital, Via Manzoni 56, Rozzano, 20089 Milan, Italy; (F.D.G.); (A.C.)
- Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, 20133 Milano, Italy; (A.M.R.F.); (F.C.); (M.L.C.)
| | - Gennaro Nappo
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, Pieve Emanuele, 20072 Milan, Italy; (G.N.); (G.C.); (A.Z.)
- Pancreatic Unit, IRCCS Humanitas Research Hospital, Via Manzoni 56, Rozzano, 20089 Milan, Italy; (F.D.G.); (A.C.)
| | - Giovanni Capretti
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, Pieve Emanuele, 20072 Milan, Italy; (G.N.); (G.C.); (A.Z.)
- Pancreatic Unit, IRCCS Humanitas Research Hospital, Via Manzoni 56, Rozzano, 20089 Milan, Italy; (F.D.G.); (A.C.)
| | - Silvia Carrara
- Endoscopy Unit, Department of Gastroenterology, IRCCS Humanitas Research Hospital, Via Manzoni 56, Rozzano, 20089 Milan, Italy;
| | - Alice Maria Renata Ferrari
- Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, 20133 Milano, Italy; (A.M.R.F.); (F.C.); (M.L.C.)
| | - Francesco Cellesi
- Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, 20133 Milano, Italy; (A.M.R.F.); (F.C.); (M.L.C.)
| | - Maria Laura Costantino
- Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, 20133 Milano, Italy; (A.M.R.F.); (F.C.); (M.L.C.)
| | - Alessandro Zerbi
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, Pieve Emanuele, 20072 Milan, Italy; (G.N.); (G.C.); (A.Z.)
- Pancreatic Unit, IRCCS Humanitas Research Hospital, Via Manzoni 56, Rozzano, 20089 Milan, Italy; (F.D.G.); (A.C.)
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Miralles M, Falcón M, Requejo L, Plana E, Medina P, Sánchez-Nevárez I, Clará A. "In Vitro" Evaluation of Energy-Based Sealing of Graft Side Branches in Bypass Surgery. World J Surg 2023; 47:2888-2896. [PMID: 37432421 DOI: 10.1007/s00268-023-07107-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/19/2023] [Indexed: 07/12/2023]
Abstract
INTRODUCTION Our objective was to compare the in vitro efficacy of electrothermal bipolar [EB] vessel sealing and ultrasonic harmonic scalpel [HS] versus mechanical interruption, with conventional ties or surgical clips (SC), in sealing saphenous vein (SV) collaterals, during its eventual preparation for bypass surgery. METHODS Experimental in vitro study on 30 segments of SV. Each fragment included two collaterals at least 2 mm in diameter. One of them was sealed by ligation with 3/0 silk ties (control) and the other one with EB (n = 10), HS (n = 10) or medium-6 mm SC (n = 10). After incorporation in a closed circuit with pulsatile flow, the pressure was progressively increased until causing rupture. Collateral diameter, burst pressure, leak point, and histological study were recorded. RESULTS Burst pressure was higher for SC (1320.20 ± 373.847 mmHg) as compared with EB (942.2 ± 344.9 mmHg, p = 0.065), and especially with HS (637.00 ± 320.61 mmHg, p = 0.0001). No statistically significant difference between EB and HS was found, and bursting always happened at supraphysiological pressures. The leak point for HS was always detected in the sealing zone (10/10), while for EB and SC, it occurred in the sealing zone only in 6/10(60%) and 4/10(40%), respectively (p = 0.015). CONCLUSIONS Energy delivery devices showed similar efficacy and safety in sealing of SV side branches. Although bursting pressure was lower than with tie ligature or SC, non-inferiority efficacy was shown at the range of physiological pressures in both, EB and HS. Due to their speed and easy handling, they may be useful in the preparation of the venous graft during revascularization surgery. However, remaining questions about healing process, potential spread of tissue damage and sealing durability, will require further analysis.
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Affiliation(s)
- Manuel Miralles
- Department of Vascular Surgery, Hospital Universitari i Politècnic La Fe, Valencia, Spain
- Department of Surgery, Facultad de Medicina, Universidad de Valencia (UV), Valencia, Spain
- Hemostasia, Thrombosis, Arteriosclerosis and Vascular Biology, Instituto de Investigación Sanitaria IIS La Fe, Valencia, Spain
| | - Moisés Falcón
- Department of Vascular Surgery, Hospital de Manises, Valencia, Spain.
| | - Lucía Requejo
- Department of Vascular Surgery, Hospital Universitario de La Ribera, Alzira, Valencia, Spain
| | - Emma Plana
- Hemostasia, Thrombosis, Arteriosclerosis and Vascular Biology, Instituto de Investigación Sanitaria IIS La Fe, Valencia, Spain
| | - Pilar Medina
- Hemostasia, Thrombosis, Arteriosclerosis and Vascular Biology, Instituto de Investigación Sanitaria IIS La Fe, Valencia, Spain
| | | | - Albert Clará
- Department of Vascular Surgery, Hospital Universitari del Mar, Barcelona, Spain
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Furrer MK. Invited Commentary to "In Vitro" Evaluation of Energy-Based Sealing of Graft Side Branches in Bypass Surgery. World J Surg 2023; 47:2897-2898. [PMID: 37702777 DOI: 10.1007/s00268-023-07150-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/24/2023] [Indexed: 09/14/2023]
Affiliation(s)
- Markus K Furrer
- Head of Vascular and Thoracic Surgery, Director of Surgical Department, Kantonsspital GR, Chur, Switzerland.
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Northeast R, Constable M, Burton HE, Lawless BM, Gramigna V, Lim Goh K, Buchan KG, Espino DM. Mechanical testing of glutaraldehyde cross-linked mitral valves. Part one: In vitro mechanical behaviour. Proc Inst Mech Eng H 2020; 235:281-290. [PMID: 33231114 DOI: 10.1177/0954411920975894] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The aim of this study was to perform an initial assessment, in vitro, of the feasibility of using a glutaraldehyde cross-linked porcine mitral valve to retain acute functionality, focusing on assessing mitral regurgitation. Six porcine hearts were tested using an in vitro simulator. Testing was repeated following cross-linking of mitral valves; where cross-linking was achieved by placing them in a glutaraldehyde solution. The simulator enabled systolic pressure on the ventricular side of the valve to be mimicked. Following testing, mitral valve leaflets underwent Scanning Electron Microscopy of the ventricular surface of both the anterior and posterior leaflets (1 cm2 samples). The peak pressure withstood by cross-linked valves was significantly lower than for untreated valves (108 mmHg cf. 128 mmHg for untreated valves; p < 0.05). The peak pressure was typically reached 0.5 s later than for the untreated valve. While both cross-linked and untreated valves exhibited endothelium denudation, the unfixed valve had less endothelial loss. Glutaraldehyde cross-linking of porcine mitral valves may be of potential value in assessing improved bioprosthetic mitral valve replacements. However, a more immobile valve exhibiting endothelial denudation (i.e. sclerosis) was a possible concerns identified following in vitro acute assessment.
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Affiliation(s)
- Rhiannon Northeast
- Department of Mechanical Engineering, University of Birmingham, Birmingham, UK
| | - Matthew Constable
- Department of Mechanical Engineering, University of Birmingham, Birmingham, UK
| | - Hanna E Burton
- Department of Mechanical Engineering, University of Birmingham, Birmingham, UK
| | - Bernard M Lawless
- Department of Mechanical Engineering, University of Birmingham, Birmingham, UK.,Filament PD, Level 4 - Skypark 3, Skypark, Glasgow, UK
| | - Vera Gramigna
- University of Magna Graecia, Catanzaro, Italy.,IBFM, National Research Council, Germaneto, Catanzaro, Italy
| | - Kheng Lim Goh
- Department of Mechanical Engineering, University of Newcastle, Singapore
| | - Keith G Buchan
- Department of Cardio-thoracic Surgery, Aberdeen Royal Infirmary, Forresterhill, Aberdeen, UK
| | - Daniel M Espino
- Department of Mechanical Engineering, University of Birmingham, Birmingham, UK
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Owen DG, Schenkel T, Shepherd DET, Espino DM. Assessment of surface roughness and blood rheology on local coronary haemodynamics: a multi-scale computational fluid dynamics study. J R Soc Interface 2020; 17:20200327. [PMID: 32781935 PMCID: PMC7482556 DOI: 10.1098/rsif.2020.0327] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 07/23/2020] [Indexed: 01/04/2023] Open
Abstract
The surface roughness of the coronary artery is associated with the onset of atherosclerosis. The study applies, for the first time, the micro-scale variation of the artery surface to a 3D coronary model, investigating the impact on haemodynamic parameters which are indicators for atherosclerosis. The surface roughness of porcine coronary arteries have been detailed based on optical microscopy and implemented into a cylindrical section of coronary artery. Several approaches to rheology are compared to determine the benefits/limitations of both single and multiphase models for multi-scale geometry. Haemodynamic parameters averaged over the rough/smooth sections are similar; however, the rough surface experiences a much wider range, with maximum wall shear stress greater than 6 Pa compared to the approximately 3 Pa on the smooth segment. This suggests the smooth-walled assumption may neglect important near-wall haemodynamics. While rheological models lack sufficient definition to truly encompass the micro-scale effects occurring over the rough surface, single-phase models (Newtonian and non-Newtonian) provide numerically stable and comparable results to other coronary simulations. Multiphase models allow for phase interactions between plasma and red blood cells which is more suited to such multi-scale models. These models require additional physical laws to govern advection/aggregation of particulates in the near-wall region.
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Affiliation(s)
- David G. Owen
- Department of Mechanical Engineering, University of Birmingham, UK
| | - Torsten Schenkel
- Department of Engineering and Mathematics, Materials and Engineering Research Institute MERI, Sheffield Hallam University, Sheffield, UK
| | | | - Daniel M. Espino
- Department of Mechanical Engineering, University of Birmingham, UK
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Taylor S, Buchan KG, Espino DM. The role of strut chordae in mitral valve competence during annular dilation. Perfusion 2020; 36:253-260. [PMID: 32693675 PMCID: PMC8041452 DOI: 10.1177/0267659120941340] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Strut chordae, on their own, are not typically thought to aid mitral valve competence. The aim of this study is to assess whether strut chordae aid mitral valve competence during acute annular dilation. Twelve porcine hearts were dissected and tested using an in vitro simulator, with the mitral annulus tested in either a 'normal' or a dilated configuration. The normal configuration included a diameter of 30 mm, a posterior leaflet 'radius' of 15 mm and a commissural corner 'radius' of 7.5 mm; the dilated annular template instead used dimensions of 50 mm, 25 mm and 12.5 mm, respectively. Each mitral valve underwent ten repeat tests with a target systolic pressure of 100 mmHg. No significant difference in the pressure was detected between the dilated and regular annuli for the mitral valves tested (95 ± 3 mmHg cf. 95 ± 2 mmHg). However, the volume of regurgitation for a dilated annulus was 28 ml greater than for a valve with a normal annulus. Following severing of strut chordae, there was a significant reduction in the systolic pressure withstood before regurgitation by mitral valves with dilated annuli (60 ± 29 mmHg cf. 95 ± 2 mmHg for normal annular dimensions; p < 0.05). In conclusion, strut chordae tendineae may play a role in aiding mitral valve competence during pathophysiology.
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Affiliation(s)
- Samuel Taylor
- Department of Mechanical Engineering, University of Birmingham, Birmingham, UK
| | - Keith G Buchan
- Department of Cardiothoracic Surgery, Aberdeen Royal Infirmary, Aberdeen, UK
| | - Daniel M Espino
- Department of Mechanical Engineering, University of Birmingham, Birmingham, UK
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Taylor S, Buchan KG, Espino DM. The role of strut chordae in mitral valve competence during annular dilation. Perfusion 2020. [PMID: 32693675 DOI: 10.1177/0267659120941340.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Strut chordae, on their own, are not typically thought to aid mitral valve competence. The aim of this study is to assess whether strut chordae aid mitral valve competence during acute annular dilation. Twelve porcine hearts were dissected and tested using an in vitro simulator, with the mitral annulus tested in either a 'normal' or a dilated configuration. The normal configuration included a diameter of 30 mm, a posterior leaflet 'radius' of 15 mm and a commissural corner 'radius' of 7.5 mm; the dilated annular template instead used dimensions of 50 mm, 25 mm and 12.5 mm, respectively. Each mitral valve underwent ten repeat tests with a target systolic pressure of 100 mmHg. No significant difference in the pressure was detected between the dilated and regular annuli for the mitral valves tested (95 ± 3 mmHg cf. 95 ± 2 mmHg). However, the volume of regurgitation for a dilated annulus was 28 ml greater than for a valve with a normal annulus. Following severing of strut chordae, there was a significant reduction in the systolic pressure withstood before regurgitation by mitral valves with dilated annuli (60 ± 29 mmHg cf. 95 ± 2 mmHg for normal annular dimensions; p < 0.05). In conclusion, strut chordae tendineae may play a role in aiding mitral valve competence during pathophysiology.
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Affiliation(s)
- Samuel Taylor
- Department of Mechanical Engineering, University of Birmingham, Birmingham, UK
| | - Keith G Buchan
- Department of Cardiothoracic Surgery, Aberdeen Royal Infirmary, Aberdeen, UK
| | - Daniel M Espino
- Department of Mechanical Engineering, University of Birmingham, Birmingham, UK
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Abstract
The aim of this study was to develop a finite element model to investigate the forces on tendons which ensue due to trigger finger. The model was used to simulate both flexor and extensor tendons within the index finger; two test cases were defined, simulating a “mildly” and “severely” affected tendon by applying constraints. The finger was simulated in three different directions: extension, abduction and hyper-extension. There was increased tension during hyper-extension, with tension in the mildly affected tendon increasing from 1.54 to 2.67 N. Furthermore, there was a consistent relationship between force and displacement, with a substantial change in the gradient of the force when the constraints of the condition were applied for all movements. The intention of this study is that the simulation framework is used to enable the in silico development of novel prosthetic devices to aid with treatment of trigger finger, given that, currently, the non-surgical first line of treatment is a splint.
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Burton HE, Cullinan R, Jiang K, Espino DM. Multiscale three-dimensional surface reconstruction and surface roughness of porcine left anterior descending coronary arteries. ROYAL SOCIETY OPEN SCIENCE 2019; 6:190915. [PMID: 31598314 PMCID: PMC6774942 DOI: 10.1098/rsos.190915] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2019] [Accepted: 08/07/2019] [Indexed: 05/11/2023]
Abstract
The aim of this study was to investigate the multiscale surface roughness characteristics of coronary arteries, to aid in the development of novel biomaterials and bioinspired medical devices. Porcine left anterior descending coronary arteries were dissected ex vivo, and specimens were chemically fixed and dehydrated for testing. Surface roughness was calculated from three-dimensional reconstructed surface images obtained by optical, scanning electron and atomic force microscopy, ranging in magnification from 10× to 5500×. Circumferential surface roughness decreased with magnification, and microscopy type was found to influence surface roughness values. Longitudinal surface roughness was not affected by magnification or microscopy types within the parameters of this study. This study found that coronary arteries exhibit multiscale characteristics. It also highlights the importance of ensuring consistent microscopy parameters to provide comparable surface roughness values.
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Affiliation(s)
- Hanna E. Burton
- PDR – International Centre for Design and Research, Cardiff Metropolitan University, Cardiff CF5 2YB, UK
- Biomedical Engineering Research Group, Department of Mechanical Engineering, University of Birmingham, Birmingham B15 2TT, UK
| | - Rachael Cullinan
- School of Chemical Engineering, University of Birmingham, Birmingham B15 2TT, UK
| | - Kyle Jiang
- Research Centre for Micro/Nanotechnology, Department of Mechanical Engineering, University of Birmingham, Birmingham B15 2TT, UK
| | - Daniel M. Espino
- Biomedical Engineering Research Group, Department of Mechanical Engineering, University of Birmingham, Birmingham B15 2TT, UK
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Effect of freezing and thawing on the biomechanical characteristics of porcine ocular tissues. J Biomech 2019; 87:93-99. [PMID: 30876736 DOI: 10.1016/j.jbiomech.2019.02.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 12/25/2018] [Accepted: 02/23/2019] [Indexed: 12/13/2022]
Abstract
PURPOSE To evaluate the effect of freezing and thawing on the biomechanical properties of ex-vivo porcine ocular tissue. METHODS Thirty-six porcine eyes (18 pairs) were obtained fresh from a local abattoir and split into two groups of nine pairs to study the effect of storage at -20 °C and -80 °C. A randomly-selected eye from each pair (Control Group, CG) was tested fresh while the fellow eyes were frozen for 14 days, either at -20 °C and -80 °C (Frozen Group, FG) before thawing and testing. Seventy-two strips were extracted from the corneas and scleras of eye globes and subjected to uniaxial tension tests under loads up to 1.0 N. Following five preconditioning cycles, the load and elongation data obtained experimentally were analysed to derive the tissue's stress-strain and tangent modulus-strain behaviour. RESULTS Corneal tissue subjected to freezing at -20 °C exhibited significant increases in tangent modulus (mechanical stiffness) by 13 ± 17% (p = 0.003) at 1% strain and 14 ± 12% (p < 0.001) at 2% strain. In contrast, the increases in corneal stiffness at -80 °C were insignificant (6 ± 14%, p = 0.099 at 1% strain, 6 ± 15%, p = 0.091 at 2% strain). The corresponding increases in tangent modulus in the sclera were all insignificant (for -20 °C: 4 ± 14%, p = 0.265 at 1% strain, 3 ± 9%, p = 0.186 at 2% strain; for -80 °C: 3 ± 18%, p = 0.537 at 1% strain and 3 ± 18%, p = 0.491 at 2% strain). CONCLUSIONS The study provided evidence that freezing and thawing led to insignificant changes in ocular tissue stiffness except in corneal tissue that was frozen at -20 °C.
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The Effect of Mechanical Overloading on Surface Roughness of the Coronary Arteries. Appl Bionics Biomech 2019; 2019:2784172. [PMID: 30809272 PMCID: PMC6364105 DOI: 10.1155/2019/2784172] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Revised: 11/29/2018] [Accepted: 01/01/2019] [Indexed: 01/03/2023] Open
Abstract
Background Surface roughness can be used to identify disease within biological tissues. Quantifying surface roughness in the coronary arteries aids in developing treatments for coronary heart disease. This study investigates the effect of extreme physiological loading on surface roughness, for example, due to a rupture of an artery. Methods The porcine left anterior descending (LAD) coronary arteries were dissected ex vivo. Mechanical overloading was applied to the arteries in the longitudinal direction to simulate extreme physiological loading. Surface roughness was calculated from three-dimensional reconstructed images. Surface roughness was measured before and after damage and after chemical processing to dehydrate tissue specimens. Results Control specimens confirmed that dehydration alone results in an increase of surface roughness in the circumferential direction only. No variation was noted between the hydrated healthy and damaged specimens, in both the longitudinal (0.91 ± 0.26 and 1.05 ± 0.25 μm) and circumferential (1.46 ± 0.38 and 1.47 ± 0.39 μm) directions. After dehydration, an increase in surface roughness was noted for damaged specimens in both the longitudinal (1.28 ± 0.33 μm) and circumferential (1.95 ± 0.56 μm) directions. Conclusions Mechanical overloading applied in the longitudinal direction did not significantly affect surface roughness. However, when combined with chemical processing, a significant increase in surface roughness was noted in both the circumferential and longitudinal directions. Mechanical overloading causes damage to the internal constituents of the arteries, which is significantly noticeable after dehydration of tissue.
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Freij JM, Burton HE, Espino DM. Objective Uniaxial Identification of Transition Points in Non-Linear Materials: Sample Application to Porcine Coronary Arteries and the Dependency of Their Pre- and Post-Transitional Moduli with Position. Cardiovasc Eng Technol 2018; 10:61-68. [DOI: 10.1007/s13239-018-00395-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 11/17/2018] [Indexed: 11/24/2022]
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Constable M, Burton HE, Lawless BM, Gramigna V, Buchan KG, Espino DM. Effect of glutaraldehyde based cross-linking on the viscoelasticity of mitral valve basal chordae tendineae. Biomed Eng Online 2018; 17:93. [PMID: 30001710 PMCID: PMC6044032 DOI: 10.1186/s12938-018-0524-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 07/05/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Mitral valve failure can require repair or replacement. Replacement bioprosthetic valves are treated with glutaraldehyde prior to implantation. The aim of this study was to determine the changes in mechanical properties following glutaraldehyde fixation of mitral valve chordae. METHODS To investigate the impact of glutaraldehyde on mitral valve chordae, 24 basal chordae were dissected from four porcine hearts. Anterior and posterior basal (including strut) chordae were used. All 24 chordae were subjected to a sinusoidally varying load (mean level 2N, dynamic amplitude 2N) over a frequency range of 0.5-10 Hz before and after glutaraldehyde treatment. RESULTS The storage and loss modulus of all chordal types decreased following glutaraldehyde fixation. The storage modulus ranged from: 108 to 119 MPa before fixation and 67.3-87.4 MPa following fixation for basal chordae; 52.3-58.4 MPa before fixation and 47.9-53.5 MPa following fixation for strut chordae. Similarly, the loss modulus ranged from: 5.47 to 6.25 MPa before fixation and 3.63-4.94 MPa following fixation for basal chordae; 2.60-2.97 MPa before fixation and 2.31-2.93 MPa following fixation for strut chordae. CONCLUSION The viscoelastic properties of mitral valve chordae are affected by glutaraldehyde fixation; in particular, the reduction in storage moduli decreased with an increase in chordal diameter.
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Affiliation(s)
- M Constable
- Department of Mechanical Engineering, University of Birmingham, Birmingham, B15 2TT, UK
| | - H E Burton
- Department of Mechanical Engineering, University of Birmingham, Birmingham, B15 2TT, UK.,PDR, International Centre for Design and Research, Cardiff Metropolitan University, Cardiff, CF5 2YB, UK
| | - B M Lawless
- Department of Mechanical Engineering, University of Birmingham, Birmingham, B15 2TT, UK
| | - V Gramigna
- University of Magna Graecia, Catanzaro, Italy.,IBFM, National Research Council, Germaneto, Catanzaro, Italy
| | - K G Buchan
- Department of Cardiothoracic Surgery, Aberdeen Royal Infirmary, Foresterhill, Aberdeen, AB25 2ZN, UK
| | - D M Espino
- Department of Mechanical Engineering, University of Birmingham, Birmingham, B15 2TT, UK.
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Jewkes R, Burton HE, Espino DM. Towards Additive Manufacture of Functional, Spline-Based Morphometric Models of Healthy and Diseased Coronary Arteries: In Vitro Proof-of-Concept Using a Porcine Template. J Funct Biomater 2018; 9:E15. [PMID: 29393899 PMCID: PMC5872101 DOI: 10.3390/jfb9010015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Revised: 01/26/2018] [Accepted: 01/31/2018] [Indexed: 12/21/2022] Open
Abstract
The aim of this study is to assess the additive manufacture of morphometric models of healthy and diseased coronary arteries. Using a dissected porcine coronary artery, a model was developed with the use of computer aided engineering, with splines used to design arteries in health and disease. The model was altered to demonstrate four cases of stenosis displaying varying severity, based on published morphometric data available. Both an Objet Eden 250 printer and a Solidscape 3Z Pro printer were used in this analysis. A wax printed model was set into a flexible thermoplastic and was valuable for experimental testing with helical flow patterns observed in healthy models, dominating the distal LAD (left anterior descending) and left circumflex arteries. Recirculation zones were detected in all models, but were visibly larger in the stenosed cases. Resin models provide useful analytical tools for understanding the spatial relationships of blood vessels, and could be applied to preoperative planning techniques, but were not suitable for physical testing. In conclusion, it is feasible to develop blood vessel models enabling experimental work; further, through additive manufacture of bio-compatible materials, there is the possibility of manufacturing customized replacement arteries.
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Affiliation(s)
- Rachel Jewkes
- Department of Mechanical Engineering, University of Birmingham, Birmingham B15 2TT, UK.
| | - Hanna E Burton
- Department of Mechanical Engineering, University of Birmingham, Birmingham B15 2TT, UK.
| | - Daniel M Espino
- Department of Mechanical Engineering, University of Birmingham, Birmingham B15 2TT, UK.
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