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Kawecki NS, Norris SCP, Xu Y, Wu Y, Davis AR, Fridman E, Chen KK, Crosbie RH, Garmyn AJ, Li S, Mason TG, Rowat AC. Engineering multicomponent tissue by spontaneous adhesion of myogenic and adipogenic microtissues cultured with customized scaffolds. Food Res Int 2023; 172:113080. [PMID: 37689860 DOI: 10.1016/j.foodres.2023.113080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Revised: 05/29/2023] [Accepted: 05/30/2023] [Indexed: 09/11/2023]
Abstract
The integration of intramuscular fat-or marbling-into cultured meat will be critical for meat texture, mouthfeel, flavor, and thus consumer appeal. However, culturing muscle tissue with marbling is challenging since myocytes and adipocytes have different media and scaffold requirements for optimal growth and differentiation. Here, we present an approach to engineer multicomponent tissue using myogenic and adipogenic microtissues. The key innovation in our approach is the engineering of myogenic and adipogenic microtissues using scaffolds with customized physical properties; we use these microtissues as building blocks that spontaneously adhere to produce multicomponent tissue, or marbled cultured meat. Myocytes are grown and differentiated on gelatin nanofiber scaffolds with aligned topology that mimic the aligned structure of skeletal muscle and promotes the formation of myotubes in both primary rabbit skeletal muscle and murine C2C12 cells. Pre-adipocytes are cultured and differentiated on edible gelatin microbead scaffolds, which are customized to have a physiologically-relevant stiffness, and promote lipid accumulation in both primary rabbit and murine 3T3-L1 pre-adipocytes. After harvesting and stacking the individual myogenic and adipogenic microtissues, we find that the resultant multicomponent tissues adhere into intact structures within 6-12 h in culture. The resultant multicomponent 3D tissue constructs show behavior of a solid material with a Young's modulus of ∼ 2 ± 0.4 kPa and an ultimate tensile strength of ∼ 23 ± 7 kPa without the use of additional crosslinkers. Using this approach, we generate marbled cultured meat with ∼ mm to ∼ cm thickness, which has a protein content of ∼ 4 ± 2 g/100 g that is comparable to a conventionally produced Wagyu steak with a protein content of ∼ 9 ± 4 g/100 g. We show the translatability of this layer-by-layer assembly approach for microtissues across primary rabbit cells, murine cell lines, as well as for gelatin and plant-based scaffolds, which demonstrates a strategy to generate edible marbled meats derived from different species and scaffold materials.
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Affiliation(s)
- N Stephanie Kawecki
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Sam C P Norris
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Yixuan Xu
- Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Yifan Wu
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Ashton R Davis
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Ester Fridman
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Kathleen K Chen
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Rachelle H Crosbie
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Neurology, David Geffen School of Medicine, University of California LA, USA; Broad Stem Cell Center, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Andrea J Garmyn
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, MI 48824, USA
| | - Song Li
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA; Jonsson Comprehensive Cancer Center, University of California, Los Angeles, Los Angeles, CA 90095, USA; Broad Stem Cell Center, University of California, Los Angeles, Los Angeles, CA 90095, USA; California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Thomas G Mason
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, CA 90095, USA; California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Amy C Rowat
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA; Jonsson Comprehensive Cancer Center, University of California, Los Angeles, Los Angeles, CA 90095, USA; Broad Stem Cell Center, University of California, Los Angeles, Los Angeles, CA 90095, USA; California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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Conrad SA, Wang D. Evaluation of Recirculation During Venovenous Extracorporeal Membrane Oxygenation Using Computational Fluid Dynamics Incorporating Fluid-Structure Interaction. ASAIO J 2021; 67:943-953. [PMID: 33315664 PMCID: PMC8318564 DOI: 10.1097/mat.0000000000001314] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Recirculation in venovenous extracorporeal membrane oxygenation (VV ECMO) leads to reduction in gas transfer efficiency. Studies of the factors contributing have been performed using in vivo studies and computational models. The fixed geometry of previous computational models limits the accuracy of results. We have developed a finite element computational fluid dynamics model incorporating fluid-structure interaction (FSI) that incorporates atrial deformation during atrial filling and emptying, with fluid flow solved using large eddy simulation. With this model, we have evaluated an extensive number of factors that could influence recirculation during two-site VV ECMO, and characterized their impact on recirculation, including cannula construction, insertion depth and orientation, VV ECMO configuration, circuit blood flow, and changes in volume, venous return, heart rate, and blood viscosity. Simulations revealed that extracorporeal blood flow relative to cardiac output, ratio of superior vena caval (SVC) to inferior vena caval (IVC) blood flow, position of the SVC cannula relative to the cavo-atrial junction, and orientation of the return cannula relative to the tricuspid valve had major influences (>20%) on recirculation fraction. Factors with a moderate influence on recirculation fraction (5%-20%) include heart rate, return cannula diameter, and direction of extracorporeal flow. Minimal influence on recirculation (<5%) was associated with atrial volume, position of the IVC cannula relative to the cavo-atrial junction, the number of side holes in the return cannula, and blood viscosity.
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Affiliation(s)
- Steven A. Conrad
- From the Departments of Medicine, Emergency Medicine, and Surgery Louisiana State University Health Sciences Center Shreveport, Shreveport, LA
| | - Dongfang Wang
- Department of Surgery, University of Kentucky, Lexington, KT
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Mercado M, Leung L, Gallagher M, Shah S, Kulstad E. Modeling esophageal protection from radiofrequency ablation via a cooling device: an analysis of the effects of ablation power and heart wall dimensions. Biomed Eng Online 2020; 19:77. [PMID: 33046057 PMCID: PMC7552446 DOI: 10.1186/s12938-020-00821-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 09/24/2020] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Esophageal thermal injury can occur after radiofrequency (RF) ablation in the left atrium to treat atrial fibrillation. Existing methods to prevent esophageal injury have various limitations in deployment and uncertainty in efficacy. A new esophageal heat transfer device currently available for whole-body cooling or warming may offer an additional option to prevent esophageal injury. We sought to develop a mathematical model of this process to guide further studies and clinical investigations and compare results to real-world clinical data. RESULTS The model predicts that the esophageal cooling device, even with body-temperature water flow (37 °C) provides a reduction in esophageal thermal injury compared to the case of the non-protected esophagus, with a non-linear direct relationship between lesion depth and the cooling water temperature. Ablation power and cooling water temperature have a significant influence on the peak temperature and the esophageal lesion depth, but even at high RF power up to 50 W, over durations up to 20 s, the cooling device can reduce thermal impact on the esophagus. The model concurs with recent clinical data showing an 83% reduction in transmural thermal injury when using typical operating parameters. CONCLUSIONS An esophageal cooling device appears effective for esophageal protection during atrial fibrillation, with model output supporting clinical data. Analysis of the impact of ablation power and heart wall dimensions suggests that cooling water temperature can be adjusted for specific ablation parameters to assure the desired myocardial tissue ablation while keeping the esophagus protected.
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Affiliation(s)
- Marcela Mercado
- Bioengineering Department, Engineering Faculty, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellin, Colombia.
| | - Lisa Leung
- St. George's University Hospitals NHS Foundation Trust, St. George's, University of London, Cranmer Terrace, Tooting, London, SW17 0RE, UK
| | - Mark Gallagher
- St. George's University Hospitals NHS Foundation Trust, St. George's, University of London, Cranmer Terrace, Tooting, London, SW17 0RE, UK
| | | | - Erik Kulstad
- Southwestern Medical Center, University of Texas, Dallas, TX, USA
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Clark RA, Suh SY, Caprioli J, Giaconi JA, Nouri-Mahdavi K, Law SK, Bonelli L, Coleman AL, Demer JL. Adduction-Induced Strain on the Optic Nerve in Primary Open Angle Glaucoma at Normal Intraocular Pressure. Curr Eye Res 2020; 46:568-578. [PMID: 32911989 DOI: 10.1080/02713683.2020.1817491] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
PURPOSE/AIM The optic nerve (ON) becomes taut during adduction beyond ~26° in healthy people and patients with primary open angle glaucoma (POAG), but only retracts the globe in POAG. We used magnetic resonance imaging (MRI) to investigate this difference. MATERIALS AND METHODS MRI was obtained in 2-mm quasi-coronal planes in central gaze, and smaller (~23-25°) and larger (~30-31°) adduction and abduction in 21 controls and 12 POAG subjects whose intraocular pressure never exceeded 21 mmHg. ON cross-sections were analyzed from the globe to 10 mm posteriorly. Area centroids were used to calculate ON path lengths and changes in cross-sections to calculate elongation assuming volume conservation. RESULTS For both groups, ON path was nearly straight (<102.5% of minimum path) in smaller adduction, with minimal further straightening in larger adduction. ON length was redundant in abduction, exceeding 103% of minimum path for both groups. For normals, the ON elongated 0.4 ± 0.5 mm from central gaze to smaller adduction, and 0.4 ± 0.5 mm further from smaller to larger adduction. For POAG subjects, the ON did not elongate on average from central gaze to smaller adduction and only 0.2 ± 0.4 mm from smaller to larger adduction (P = .045 vs normals). Both groups demonstrated minimal ON elongation not exceeding 0.25 mm from central gaze to smaller and larger abduction. The globe retracted significantly more during large adduction in POAG subjects than normals (0.6 ± 0.7 mm vs 0.2 ± 0.5 mm, P = .027), without appreciable retraction in abduction. For each mm increase in globe axial length, ON elongation in large adduction similarly increased by 0.2 mm in each group. CONCLUSIONS The normal ON stretches to absorb force and avert globe retraction in adduction. In POAG with mild to severe visual field loss, the relatively inelastic ON tethers and retracts the globe during adduction beyond ~26°, transfering stress to the optic disc that could contribute to progressive neuropathy during repeated eye movements.
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Affiliation(s)
- Robert A Clark
- Department of Ophthalmology, University of California, Los Angeles, USA.,Stein Eye Institute, University of California, Los Angeles, USA
| | - Soh Youn Suh
- Department of Ophthalmology, University of California, Los Angeles, USA.,Stein Eye Institute, University of California, Los Angeles, USA
| | - Joseph Caprioli
- Department of Ophthalmology, University of California, Los Angeles, USA.,Stein Eye Institute, University of California, Los Angeles, USA
| | - JoAnn A Giaconi
- Department of Ophthalmology, University of California, Los Angeles, USA.,Stein Eye Institute, University of California, Los Angeles, USA
| | - Kouros Nouri-Mahdavi
- Department of Ophthalmology, University of California, Los Angeles, USA.,Stein Eye Institute, University of California, Los Angeles, USA
| | - Simon K Law
- Department of Ophthalmology, University of California, Los Angeles, USA.,Stein Eye Institute, University of California, Los Angeles, USA
| | - Laura Bonelli
- Department of Ophthalmology, University of California, Los Angeles, USA.,Stein Eye Institute, University of California, Los Angeles, USA
| | - Anne L Coleman
- Department of Ophthalmology, University of California, Los Angeles, USA.,Stein Eye Institute, University of California, Los Angeles, USA.,Department of Epidemiology Fielding School of Public Health, University of California, Los Angeles, USA
| | - Joseph L Demer
- Department of Ophthalmology, University of California, Los Angeles, USA.,Stein Eye Institute, University of California, Los Angeles, USA.,Department of Neurology, University of California, Los Angeles, USA.,Neuroscience Interdepartmental Program, University of California, Los Angeles, USA.,Bioengineering Interdepartmental Program, University of California, Los Angeles, USA
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Abstract
This review, the first in a series of minireviews on the passive mechanical properties of skeletal muscles, seeks to summarize what is known about the muscle deformations that allow relaxed muscles to lengthen and shorten. Most obviously, when a muscle lengthens, muscle fascicles elongate, but this is not the only mechanism by which muscles change their length. In pennate muscles, elongation of muscle fascicles is accompanied by changes in pennation and changes in fascicle curvature, both of which may contribute to changes in muscle length. The contributions of these mechanisms to change in muscle length are usually small under passive conditions. In very pennate muscles with long aponeuroses, fascicle shear could contribute substantially to changes in muscle length. Tendons experience moderate axial strains even under passive loads, and, because tendons are often much longer than muscle fibers, even moderate tendon strains may contribute substantially to changes in muscle length. Data obtained with new imaging techniques suggest that muscle fascicle and aponeurosis strains are highly nonuniform, but this is yet to be confirmed. The development, validation, and interpretation of continuum muscle models informed by rigorous measurements of muscle architecture and material properties should provide further insights into the mechanisms that allow relaxed muscles to lengthen and shorten.
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Affiliation(s)
- R. D. Herbert
- Neuroscience Research Australia (NeuRA), Sydney, Australia
- University of New South Wales, Sydney, Australia
| | - B. Bolsterlee
- Neuroscience Research Australia (NeuRA), Sydney, Australia
- University of New South Wales, Sydney, Australia
| | - S. C. Gandevia
- Neuroscience Research Australia (NeuRA), Sydney, Australia
- University of New South Wales, Sydney, Australia
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Nadarasa J, Deck C, Meyer F, Bourdet N, Raul JS, Willinger R. Development of a finite-element eye model to investigate retinal hemorrhages in shaken baby syndrome. Biomech Model Mechanobiol 2017; 17:517-530. [PMID: 29209848 DOI: 10.1007/s10237-017-0975-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Accepted: 10/28/2017] [Indexed: 10/18/2022]
Abstract
Retinal hemorrhages (RH) are among injuries sustained by a large number of shaken baby syndrome victims, but also by a small proportion of road accident victims. In order to have a better understanding of the underlying of RH mechanisms, we aimed to develop a complete human eye and orbit finite element model. Five occipital head impacts, at different heights and on different surfaces, and three shaking experiments were conducted with a 6-week-old dummy (Q0 dummy). This allowed obtaining a precise description of the motion in those two specific situations, which was then used as input for the eye model simulation. Results showed that four parameters (pressure, Von Mises stress and strain, 1st principal stress) are relevant for shaking-fall comparison. Indeed, in the retina, the softest shaking leads to pressure that is 4 times higher than the most severe impact (1.43 vs. 0.34 kPa). For the Von Mises stress, strain and 1st principal stress, this ratio rises to 4.27, 6.53 and 14.74, respectively. Moreover, regions of high stress and strain in the retina and the choroid were identified and compared to what is seen on fundoscopy. The comparison between linear and rotational acceleration in fall and shaking events demonstrated the important role of the rotational acceleration in inducing such injuries. Even though the eye model was not validated, the conclusion of this study is that compared to falls, shaking an infant leads to extreme eye loading as demonstrated by the values taken by the four mentioned mechanical parameters in the retina and the choroid.
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Affiliation(s)
- Jeyendran Nadarasa
- University of Strasbourg - Icube, Unistra-CNRS, 2 Rue Boussingault, 67000, Strasbourg, France.,Institute of Legal Medicine, 11 Rue Humann, 67085, Strasbourg Cedex, France
| | - Caroline Deck
- University of Strasbourg - Icube, Unistra-CNRS, 2 Rue Boussingault, 67000, Strasbourg, France
| | - Frank Meyer
- University of Strasbourg - Icube, Unistra-CNRS, 2 Rue Boussingault, 67000, Strasbourg, France
| | - Nicolas Bourdet
- University of Strasbourg - Icube, Unistra-CNRS, 2 Rue Boussingault, 67000, Strasbourg, France
| | - Jean-Sébastien Raul
- University of Strasbourg - Icube, Unistra-CNRS, 2 Rue Boussingault, 67000, Strasbourg, France.,Institute of Legal Medicine, 11 Rue Humann, 67085, Strasbourg Cedex, France
| | - Rémy Willinger
- University of Strasbourg - Icube, Unistra-CNRS, 2 Rue Boussingault, 67000, Strasbourg, France.
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Malis V, Sinha U, Csapo R, Narici M, Sinha S. Relationship of changes in strain rate indices estimated from velocity-encoded MR imaging to loss of muscle force following disuse atrophy. Magn Reson Med 2017; 79:912-922. [PMID: 28560822 DOI: 10.1002/mrm.26759] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 04/30/2017] [Accepted: 05/01/2017] [Indexed: 11/06/2022]
Abstract
PURPOSE This study explores changes in strain rate (SR) (rate of regional deformation) parameters extracted from velocity-encoded MRI and their relationship to muscle force loss following 4-week unilateral lower limb suspension in healthy humans. METHODS Two-dimensional SR maps were derived from three directional velocity-encoded MR phase-contrast images of the medial gastrocnemius in seven subjects. Atrophy-related and regional differences in the SR eigenvalues, angle between the SR and muscle fiber (SR-fiber angle), and strain rates in the fiber basis were statistically analyzed using analysis of variance and linear regression. RESULTS During isometric contraction, SR in the fiber cross section (SRin-plane ) was significantly lower, and the SR-fiber angle was significantly higher postsuspension (P < 0.05). On multiple variable regression analysis, the volume of medial gastrocnemius, SRin-plane , and SR-fiber angle were significantly associated with force and changes in the, and the SR eigenvalues and shear SR were significantly associated with change in force with disuse. CONCLUSIONS Changes in SR-fiber angle, SRin-plane , and shear SR as well as their ability to predict force and force changes may reflect the role of remodeling of the extracellular matrix in disuse atrophy and its functional consequence in reducing lateral transmission of force. Magn Reson Med 79:912-922, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Vadim Malis
- Muscle Imaging and Modeling Lab, Department of Radiology, University of California, San Diego, California, USA.,Physics, University of California, San Diego, California, USA
| | - Usha Sinha
- Physics, San Diego State University, San Diego, California, USA
| | - Robert Csapo
- Muscle Imaging and Modeling Lab, Department of Radiology, University of California, San Diego, California, USA
| | - Marco Narici
- School of Graduate Entry Medicine and Health University of Nottingham, Derby, UK
| | - Shantanu Sinha
- Muscle Imaging and Modeling Lab, Department of Radiology, University of California, San Diego, California, USA
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Shin A, Yoo L, Demer JL. Viscoelastic characterization of extraocular Z-myotomy. Invest Ophthalmol Vis Sci 2014; 56:243-51. [PMID: 25477318 DOI: 10.1167/iovs.14-15510] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
PURPOSE Z-myotomy is an extraocular muscle (EOM) weakening procedure in which two incisions are made from longitudinally-separated, opposite EOM margins for treatment of strabismus. We examined the in vitro biomechanics of Z-myotomy using tensile loading. METHODS Fresh bovine rectus EOMs were reduced to 20 × 10 × 2-mm dimensions, and clamped in a microtensile load cell under physiological conditions. Extraocular muscles were elongated until failure following scissors incisions made from opposite sides, spaced 8 mm apart and each encompassing 0%, 40%, 50%, 60%, or 80% EOM width. Initial strain to 30% elongation was imposed at 100 mm/s, after which elongation was maintained for greater than 100 seconds during force recording at maintained deformation. Stress relaxation tests with nonincised specimens having widths ranging from 1 to 9 mm were conducted for viscoelastic characterization of corresponding equivalence to 20% to 80% Z-myotomy. Data were modeled using the Wiechert viscoelastic formulation. RESULTS There was progressively reduced EOM failure force to an asymptotic minimum at 60% or greater Z-myotomy. Each Z-myotomy specimen could be matched for equivalent failure force to a non-Z-myotomy specimen with a different width. Both tensile and stress relaxation data could be modeled accurately using the Wiechert viscoelastic formulation. CONCLUSIONS The parallel fiber structure results in low shear force transfer across EOM width, explaining the biomechanics of Z-myotomy. Z-myotomy progressively reduces force transmission to an asymptotic minimum for less than 60% surgical dose, with no further reduction for greater amounts of surgery. Equivalence to EOM specimens having regular cross-sections permits viscoelastic biomechanical characterization of Z-myotomy specimens with irregular cross-sections.
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Affiliation(s)
- Andrew Shin
- Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, Los Angeles, United States Department of Mechanical Engineering, University of California, Los Angeles, Los Angeles, United States
| | - Lawrence Yoo
- Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, Los Angeles, United States
| | - Joseph L Demer
- Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, Los Angeles, United States Biomedical Engineering Interdepartmental Program, University of California, Los Angeles, Los Angeles, United States
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Sinha U, Malis V, Csapo R, Moghadasi A, Kinugasa R, Sinha S. Age-related differences in strain rate tensor of the medial gastrocnemius muscle during passive plantarflexion and active isometric contraction using velocity encoded MR imaging: potential index of lateral force transmission. Magn Reson Med 2014; 73:1852-63. [PMID: 25046255 DOI: 10.1002/mrm.25312] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Revised: 05/16/2014] [Accepted: 05/18/2014] [Indexed: 11/05/2022]
Abstract
PURPOSE The strain rate (SR) tensor measures the principal directions and magnitude of the instantaneous deformation; this study aims to track age-related changes in the 2D SR tensor in the medial gastrocnemius during passive joint rotation and active isometric contraction. METHODS SR tensors were derived from velocity encoded magnetic resonance phase-contrast images in nine young (28 years) and eight senior (78 years) women. Strain rates along and in the cross-section of the fiber were calculated from the SR tensor and used to derive the out-plane SR. Age-related and regional differences in the SR eigenvalues, orientation, and the angle between the SR and muscle fiber (SR-fiber angle) were statistically analyzed. RESULTS SR along the fiber was significantly different between the cohorts during isometric contraction with higher values in the young (P < 0.05). The SR-fiber angle was larger in the young for both motion types but this difference was not statistically significant. Significant regional differences in the SR indices was seen in passive joint rotation (P < 0.05) for both cohorts. CONCLUSION SR mapping reflects age-related and regional differences during active and passive motion respectively; this may arise from differences in contractility (active motion) and elastic properties (active and passive motion).
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Affiliation(s)
- Usha Sinha
- Physics Department, San Diego State University, San Diego, California, USA
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Shin A, Yoo L, Demer JL. Biomechanics of superior oblique Z-tenotomy. J AAPOS 2013; 17:612-7. [PMID: 24321425 PMCID: PMC3858822 DOI: 10.1016/j.jaapos.2013.09.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Revised: 09/10/2013] [Accepted: 09/15/2013] [Indexed: 11/25/2022]
Abstract
BACKGROUND A recent report suggests that 70%-80% Z-tenotomy of the superior oblique tendon is necessary to effectively treat A-pattern strabismus associated with over depression in adduction. To clarify the clinical effect, we compared the biomechanics of Z-tenotomy on the superior oblique tendon, superior rectus tendon, and isotropic latex material. METHODS Fresh bovine superior oblique tendons were trimmed to 20 mm × 10 mm dimensions similar to human superior oblique tendon and clamped in a microtensile load cell under physiological conditions of temperature and humidity. Minimal preload was applied to avoid slackness. Tendons were elongated until failure following Z-tenotomies, made from opposite tendon margins, spaced 8 mm apart and each encompassing 0%, 20%, 40%, 50%, 60%, or 80% tendon width. Digitally sampled failure force was monitored using a precision strain gauge. Control experiments were performed in similar-sized specimens of bovine superior rectus tendon and isotropic latex. RESULTS Progressively increasing Z-tenotomy of latex caused a linearly graded reduction in force. In contrast, Z-tenotomy of up to 50% in superior oblique and superior rectus tendons caused nonlinear reduction in force transmission that reached a negligible value at 50% tenotomy and greater. CONCLUSIONS Z-tenotomy up to 50% progressively reduces extraocular tendon force transmission, but Z-tenotomy of ≥50% is biomechanically equivalent in vitro to complete tenotomy.
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Affiliation(s)
- Andrew Shin
- Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles; Department of Mechanical and Aerospace Engineering, University of California, Los Angeles
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