Biomechanics of Hollow Organs: Experimental Testing and Computational Modeling

A special issue of Bioengineering (ISSN 2306-5354).

Deadline for manuscript submissions: closed (31 December 2020) | Viewed by 44635

Special Issue Editors

Department of Industrial Engineering, University of Padova, Padova, Italy
Interests: mechanics of biological tissues; computational biomechanics; experimental biomechanics; biomechanics for surgery
Special Issues, Collections and Topics in MDPI journals
Centre for Mechanics of Biological Materials, Department of Industrial Engineering, University of Padova, 35131 Padova, Italy
Interests: constitutive analysis of biological tissues; mechanics of biological structures; biomechanics for surgery
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue aims to build a collection of articles that describe the recent advances in the bioengineering investigation of hollow organs’ mechanical functionality, accounting for both experimental and computational approaches.

Hollow organs, such as those found in the gastrointestinal and the lower urinary tracts or in the cardiovascular and the respiratory systems, play fundamental roles in living organisms. Hollow organs show a similar histo-anatomical organization, consisting of an epithelium surrounded by a collagen-rich connective stratum and one or multiple muscular layers. Degenerative phenomena, such as aging, may strongly affect their functionality, compromising the entire organism.

The characterization of hollow organs’ mechanical behaviour plays a crucial role for a comprehensive analysis of their functionality and for the investigation of degenerative phenomena. Experimentations must be developed at both tissue and organ levels, leading to data about histo-morphometry and mechanical responses. Such information will provide the basis for developing and validating computational models. In turn, computational models will allow to broad experimental results to an extremely wider scenario, considering different organs conditions and loading situations. In this sense, mechanical investigations will provide mandatory information for defining effective procedures and devices for both diagnostics and surgery.

To achieve its goal, this Special Issue envisages a strong integration of expertise from different areas, proceeding from biomedical sciences and medicine to bioengineering, computational and experimental biomechanics, bio-mechatronics, and materials science.

Dr. Chiara Giulia Fontanella
Dr. Emanuele Luigi Carniel
Guest Editors

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Published Papers (10 papers)

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Editorial

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7 pages, 232 KiB  
Editorial
Biomechanics of Hollow Organs: Experimental Testing and Computational Modeling
by Chiara Giulia Fontanella and Emanuele Luigi Carniel
Bioengineering 2023, 10(2), 175; https://0-doi-org.brum.beds.ac.uk/10.3390/bioengineering10020175 - 29 Jan 2023
Cited by 1 | Viewed by 6317
Abstract
Hollow organs are visceral organs that are hollow tubes or pouches (such as the intestine or the stomach, respectively) or that include a cavity (such as the heart) and which subserve a vital function [...] Full article
5 pages, 194 KiB  
Editorial
Biomechanics Assist Measurement, Modeling, Engineering Applications, and Clinical Decision Making in Medicine
by Qingjia Chi, Pengchao Liu and Huaping Liang
Bioengineering 2023, 10(1), 20; https://0-doi-org.brum.beds.ac.uk/10.3390/bioengineering10010020 - 22 Dec 2022
Cited by 2 | Viewed by 1363
Abstract
Biomechanical studies of surgeries and medical devices are usually performed with human or animal models [...] Full article

Research

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14 pages, 4299 KiB  
Article
Numerical Models Can Assist Choice of an Aortic Phantom for In Vitro Testing
by Giulia Comunale, Luigi Di Micco, Daniela Paola Boso, Francesca Maria Susin and Paolo Peruzzo
Bioengineering 2021, 8(8), 101; https://0-doi-org.brum.beds.ac.uk/10.3390/bioengineering8080101 - 21 Jul 2021
Cited by 5 | Viewed by 2432
Abstract
(1) Background: The realization of appropriate aortic replicas for in vitro experiments requires a suitable choice of both the material and geometry. The matching between the grade of details of the geometry and the mechanical response of the materials is an open issue [...] Read more.
(1) Background: The realization of appropriate aortic replicas for in vitro experiments requires a suitable choice of both the material and geometry. The matching between the grade of details of the geometry and the mechanical response of the materials is an open issue that deserves attention. (2) Methods: To explore this issue, we performed a series of Fluid–Structure Interaction simulations, which compared the dynamics of three aortic models. Specifically, we reproduced a patient-specific geometry with a wall of biological tissue or silicone, and a parametric geometry based on in vivo data made in silicone. The biological tissue and the silicone were modeled with a fiber-oriented anisotropic and isotropic hyperelastic model, respectively. (3) Results: Clearly, both the aorta’s geometry and its constitutive material contribute to the determination of the aortic arch deformation; specifically, the parametric aorta exhibits a strain field similar to the patient-specific model with biological tissue. On the contrary, the local geometry affects the flow velocity distribution quite a lot, although it plays a minor role in the helicity along the arch. (4) Conclusions: The use of a patient-specific prototype in silicone does not a priori ensure a satisfactory reproducibility of the real aorta dynamics. Furthermore, the present simulations suggest that the realization of a simplified replica with the same compliance of the real aorta is able to mimic the overall behavior of the vessel. Full article
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14 pages, 5338 KiB  
Article
A Preliminary Validation of a New Surgical Procedure for the Treatment of Primary Bladder Neck Obstruction Using a Computational Modeling Approach
by Michele Serpilli, Gianluca Zitti, Marco Dellabella, Daniele Castellani, Elvira Maranesi, Micaela Morettini, Stefano Lenci and Laura Burattini
Bioengineering 2021, 8(7), 87; https://0-doi-org.brum.beds.ac.uk/10.3390/bioengineering8070087 - 22 Jun 2021
Cited by 4 | Viewed by 4644
Abstract
A new surgical procedure for the treatment of primary bladder neck obstruction with maintenance of anterograde ejaculation is proposed. In place of monolateral or bilateral bladder neck incision, associated with a loss of ejaculation rate of up to 30%, the new surgical procedure [...] Read more.
A new surgical procedure for the treatment of primary bladder neck obstruction with maintenance of anterograde ejaculation is proposed. In place of monolateral or bilateral bladder neck incision, associated with a loss of ejaculation rate of up to 30%, the new surgical procedure consists of laser drilling the bladder neck with a number of holes and without muscle fiber disruption. The effect of this novel procedure has been studied numerically, with a simplified two-dimensional numerical model of the internal urethral sphincter, varying the position and the number of holes in the fibrotic region of the urethral tissue. Results show an improvement of the urethral sphincter opening by increasing the number of holes, ranging from about 6% to 16% of recovery. Moreover, a non-aligned position of holes positively influences the opening recovery. The concentrations of maximum principal strain and stress have been registered in the proximity of the interface between the physiologic and diseased sphincter, and in those regions where the radial thickness is significantly thinner. The effects on the first five patients have been included in the study, showing improvement in micturition, lower urinary tract symptoms, sustained ejaculatory function, and quality of life. Full article
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18 pages, 6457 KiB  
Article
Variation of Passive Biomechanical Properties of the Small Intestine along Its Length: Microstructure-Based Characterization
by Dimitrios P. Sokolis
Bioengineering 2021, 8(3), 32; https://0-doi-org.brum.beds.ac.uk/10.3390/bioengineering8030032 - 26 Feb 2021
Cited by 6 | Viewed by 2590
Abstract
Multiaxial testing of the small intestinal wall is critical for understanding its biomechanical properties and defining material models, but limited data and material models are available. The aim of the present study was to develop a microstructure-based material model for the small intestine [...] Read more.
Multiaxial testing of the small intestinal wall is critical for understanding its biomechanical properties and defining material models, but limited data and material models are available. The aim of the present study was to develop a microstructure-based material model for the small intestine and test whether there was a significant variation in the passive biomechanical properties along the length of the organ. Rat tissue was cut into eight segments that underwent inflation/extension testing, and their nonlinearly hyper-elastic and anisotropic response was characterized by a fiber-reinforced model. Extensive parametric analysis showed a non-significant contribution to the model of the isotropic matrix and circumferential-fiber family, leading also to severe over-parameterization. Such issues were not apparent with the reduced neo-Hookean and (axial and diagonal)-fiber family model, that provided equally accurate fitting results. Absence from the model of either the axial or diagonal-fiber families led to ill representations of the force- and pressure-diameter data, respectively. The primary direction of anisotropy, designated by the estimated orientation angle of diagonal-fiber families, was about 35° to the axial direction, corroborating prior microscopic observations of submucosal collagen-fiber orientation. The estimated model parameters varied across and within the duodenum, jejunum, and ileum, corroborating histologically assessed segmental differences in layer thicknesses. Full article
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12 pages, 2901 KiB  
Article
Biomechanical Investigation of the Stomach Following Different Bariatric Surgery Approaches
by Ilaria Toniolo, Chiara Giulia Fontanella, Mirto Foletto and Emanuele Luigi Carniel
Bioengineering 2020, 7(4), 159; https://0-doi-org.brum.beds.ac.uk/10.3390/bioengineering7040159 - 09 Dec 2020
Cited by 8 | Viewed by 3292
Abstract
Background: The stomach is a hollow organ of the gastrointestinal tract, on which bariatric surgery (BS) is performed for the treatment of obesity. Even though BS is the most effective treatment for severe obesity, drawbacks and complications are still present because the intervention [...] Read more.
Background: The stomach is a hollow organ of the gastrointestinal tract, on which bariatric surgery (BS) is performed for the treatment of obesity. Even though BS is the most effective treatment for severe obesity, drawbacks and complications are still present because the intervention design is largely based on the surgeon’s expertise and intraoperative decisions. Bioengineering methods can be exploited to develop computational tools for more rational presurgical design and planning of the intervention. Methods: A computational mechanical model of the stomach was developed, considering the actual complexity of the biological structure, as the nonhomogeneous and multilayered configuration of the gastric wall. Mechanical behavior was characterized by means of an anisotropic visco-hyperelastic constitutive formulation of fiber-reinforced conformation, nonlinear elastic response, and time-dependent behavior, which assume the typical features of gastric wall mechanics. Model applications allowed for an analysis of the influence of BS techniques on stomach mechanical functionality through different computational analyses. Results: Computational results showed that laparoscopic sleeve gastrectomy and endoscopic sleeve gastroplasty drastically alter stomach capacity and stiffness, while laparoscopic adjustable gastric banding modestly affects stomach stiffness and capacity. Moreover, the mean elongation strain values, which are correlated to the mechanical stimulation of gastric receptors, were elevated in laparoscopic adjustable gastric banding compared to other procedures. Conclusions: The investigation of stomach mechanical response through computational models provides information on different topics such as stomach capacity and stiffness and the mechanical stimulation of gastric receptors, which interact with the brain to control satiety. These data can provide reliable support to surgeons in the presurgical decision-making process. Full article
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14 pages, 15780 KiB  
Article
Biomechanical Force Prediction for Lengthening of Small Intestine during Distraction Enterogenesis
by Hadi S. Hosseini and James C. Y. Dunn
Bioengineering 2020, 7(4), 140; https://0-doi-org.brum.beds.ac.uk/10.3390/bioengineering7040140 - 07 Nov 2020
Cited by 9 | Viewed by 3523
Abstract
Distraction enterogenesis has been extensively studied as a potential treatment for short bowel syndrome, which is the most common form of intestinal failure. Different strategies including parenteral nutrition and surgical lengthening to manage patients with short bowel syndrome are associated with high complication [...] Read more.
Distraction enterogenesis has been extensively studied as a potential treatment for short bowel syndrome, which is the most common form of intestinal failure. Different strategies including parenteral nutrition and surgical lengthening to manage patients with short bowel syndrome are associated with high complication rates. More recently, self-expanding springs have been used to lengthen the small intestine using an intraluminal axial mechanical force, where this biomechanical force stimulates the growth and elongation of the small intestine. Differences in physical characteristics of patients with short bowel syndrome would require a different mechanical force—this is crucial in order to achieve an efficient and safe lengthening outcome. In this study, we aimed to predict the required mechanical force for each potential intestinal size. Based on our previous experimental observations and computational findings, we integrated our experimental measurements of patient biometrics along with mechanical characterization of the soft tissue into our numerical simulations to develop a series of computational models. These computational models can predict the required mechanical force for any potential patient where this can be advantageous in predicting an individual’s tissue response to spring-mediated distraction enterogenesis and can be used toward a safe delivery of the mechanical force. Full article
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Review

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15 pages, 1563 KiB  
Review
The Macro- and Micro-Mechanics of the Colon and Rectum II: Theoretical and Computational Methods
by Yunmei Zhao, Saeed Siri, Bin Feng and David M. Pierce
Bioengineering 2020, 7(4), 152; https://0-doi-org.brum.beds.ac.uk/10.3390/bioengineering7040152 - 25 Nov 2020
Cited by 7 | Viewed by 3577
Abstract
Abnormal colorectal biomechanics and mechanotransduction associate with an array of gastrointestinal diseases, including inflammatory bowel disease, irritable bowel syndrome, diverticula disease, anorectal disorders, ileus, and chronic constipation. Visceral pain, principally evoked from mechanical distension, has a unique biomechanical component that plays a critical [...] Read more.
Abnormal colorectal biomechanics and mechanotransduction associate with an array of gastrointestinal diseases, including inflammatory bowel disease, irritable bowel syndrome, diverticula disease, anorectal disorders, ileus, and chronic constipation. Visceral pain, principally evoked from mechanical distension, has a unique biomechanical component that plays a critical role in mechanotransduction, the process of encoding mechanical stimuli to the colorectum by sensory afferents. To fully understand the underlying mechanisms of visceral mechanical neural encoding demands focused attention on the macro- and micro-mechanics of colon tissue. Motivated by biomechanical experiments on the colon and rectum, increasing efforts focus on developing constitutive frameworks to interpret and predict the anisotropic and nonlinear biomechanical behaviors of the multilayered colorectum. We will review the current literature on computational modeling of the colon and rectum as well as the mechanical neural encoding by stretch sensitive afferent endings, and then highlight our recent advances in these areas. Current models provide insight into organ- and tissue-level biomechanics as well as the stretch-sensitive afferent endings of colorectal tissues yet an important challenge in modeling theory remains. The research community has not connected the biomechanical models to those of mechanosensitive nerve endings to create a cohesive multiscale framework for predicting mechanotransduction from organ-level biomechanics. Full article
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13 pages, 1283 KiB  
Review
Novel Bionics Assessment of Anorectal Mechanosensory Physiology
by Hans Gregersen
Bioengineering 2020, 7(4), 146; https://0-doi-org.brum.beds.ac.uk/10.3390/bioengineering7040146 - 14 Nov 2020
Cited by 8 | Viewed by 3032
Abstract
Biomechatronics (bionics) is an applied science that creates interdisciplinary bonds between biology and engineering. The lower gastrointestinal (GI) tract is difficult to study but has gained interest in recent decades from a bionics point of view. Ingestible capsules that record physiological variables during [...] Read more.
Biomechatronics (bionics) is an applied science that creates interdisciplinary bonds between biology and engineering. The lower gastrointestinal (GI) tract is difficult to study but has gained interest in recent decades from a bionics point of view. Ingestible capsules that record physiological variables during GI transit have been developed and used for detailed analysis of colon transit and motility. Recently, a simulated stool named Fecobionics was developed. It has the consistency and shape of normal stool. Fecobionics records a variety of parameters including pressures, bending, and shape changes. It has been used to study defecation patterns in large animals and humans, including patients with symptoms of obstructed defecation and fecal incontinence. Recently, it was applied in a canine colon model where it revealed patterns consistent with shallow waves originating from slow waves generated by the interstitial Cells of Cajal. Novel analysis such as the “rear-front” pressure diagram and quantification of defecation indices has been developed for Fecobionics. GI research has traditionally been based on experimental approaches. Mathematical modeling is a unique way to deal with the complexity. This paper describes the Fecobionics technology, related mechano-physiological modeling analyses, and outlines perspectives for future applications. Full article
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16 pages, 840 KiB  
Review
The Macro- and Micro-Mechanics of the Colon and Rectum I: Experimental Evidence
by Saeed Siri, Yunmei Zhao, Franz Maier, David M. Pierce and Bin Feng
Bioengineering 2020, 7(4), 130; https://0-doi-org.brum.beds.ac.uk/10.3390/bioengineering7040130 - 19 Oct 2020
Cited by 21 | Viewed by 12252
Abstract
Many lower gastrointestinal diseases are associated with altered mechanical movement and deformation of the large intestine, i.e., the colon and rectum. The leading reason for patients’ visits to gastrointestinal clinics is visceral pain, which is reliably evoked by mechanical distension rather than non-mechanical [...] Read more.
Many lower gastrointestinal diseases are associated with altered mechanical movement and deformation of the large intestine, i.e., the colon and rectum. The leading reason for patients’ visits to gastrointestinal clinics is visceral pain, which is reliably evoked by mechanical distension rather than non-mechanical stimuli such as inflammation or heating. The macroscopic biomechanics of the large intestine were characterized by mechanical tests and the microscopic by imaging the load-bearing constituents, i.e., intestinal collagen and muscle fibers. Regions with high mechanical stresses in the large intestine (submucosa and muscularis propria) coincide with locations of submucosal and myenteric neural plexuses, indicating a functional interaction between intestinal structural biomechanics and enteric neurons. In this review, we systematically summarized experimental evidence on the macro- and micro-scale biomechanics of the colon and rectum in both health and disease. We reviewed the heterogeneous mechanical properties of the colon and rectum and surveyed the imaging methods applied to characterize collagen fibers in the intestinal wall. We also discussed the presence of extrinsic and intrinsic neural tissues within different layers of the colon and rectum. This review provides a foundation for further advancements in intestinal biomechanics by synergistically studying the interplay between tissue biomechanics and enteric neurons. Full article
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