Tissue Fusion

Annual Review of Biomedical Engineering (2018): Energy-Based Tissue Fusion for Sutureless Closure: Applications, Mechanisms, and a Potential for Functional Recovery

Anonymous — Sun, 10 Jun 2018 02:28:02 +0000

Annual Review of Biomedical Engineering (2018): Energy-Based Tissue Fusion for Sutureless Closure: Applications, Mechanisms, and a Potential for Functional Recovery Anonymous (not verified) Sat, 06/09/2018 - 20:28

Abstract: As minimally invasive surgical techniques progress, the demand for efficient, reliable methods for vascular ligation and tissue closure becomes pronounced. The surgical advantages of energy-based vessel sealing exceed those of traditional, compression-based ligatures in procedures sensitive to duration, foreign bodies, and recovery time alike. Although the use of energy-based devices to seal or transect vasculature and connective tissue bundles is widespread, the breadth of heating strategies and energy dosimetry used across devices underscores an uncertainty as to the molecular nature of the sealing mechanism and induced tissue effect. Furthermore, energy-based techniques exhibit promise for the closure and functional repair of soft and connective tissues in the nervous, enteral, and dermal tissue domains. A constitutive theory of molecular bonding forces that arise in response to supraphysiological temperatures is required in order to optimize and progress the use of energy-based tissue fusion. While rapid tissue bonding has been suggested to arise from dehydration, dipole interactions, molecular cross-links, or the coagulation of cellular proteins, long-term functional tissue repair across fusion boundaries requires that the reaction to thermal damage be tailored to catalyze the onset of biological healing and remodeling. In this review, we compile and contrast findings from published thermal fusion research in an effort to encourage a molecular approach to characterization of the prevalent and promising energy-based tissue bond.

Kramer, E.A., Rentschler, M.E., "Energy-Based Tissue Fusion for Sutureless Closure: Applications, Mechanisms, and a Potential for Functional Recovery," Annual Review of Biomedical Engineering. 20: 1-20, 2018.

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ASME Journal of Biomechanical Engineering (2018): A Small Deformation Thermo-Poromechanics Finite Element Model and its Application to Arterial Tissue Fusion

Anonymous — Sat, 11 Nov 2017 03:08:14 +0000

ASME Journal of Biomechanical Engineering (2018): A Small Deformation Thermo-Poromechanics Finite Element Model and its Application to Arterial Tissue Fusion Anonymous (not verified) Fri, 11/10/2017 - 20:08

Abstract: Understanding the impact of thermally and mechanically loading biological tissue to supraphysiological levels is becoming of increasing importance as complex multi-physical tissue-device interactions increase. The ability to conduct accurate, patient specific computer simulations would provide surgeons with valuable insight into the physical processes occurring within the tissue as it is heated or cooled. Several studies have modeled tissue as porous media, yet fully coupled thermo-poromechanics (TPM) models are limited. Therefore, this study introduces a small deformation theory of modeling the TPM occurring within biological tissue. Next, the model is used to simulate the mass, momentum and energy balance occurring within an artery wall when heated by a tissue fusion device and compared to experimental values. Though limited by its small strain assumption, the model predicted final tissue temperature and water content within one standard deviation of experimental data for seven of seven simulations. Additionally, the model showed the ability to predict the final displacement of the tissue to within 15% of experimental results. These results promote potential design of novel medical devices and more accurate simulations allowing for scientists and surgeons to quickly, yet accurately, assess the effects of surgical procedures as well as provide a first step towards a fully coupled large deformation TPM finite element model.

Fankell, D.P., Regueiro, R.A., Kramer, E.A., Ferguson, V.L., Rentschler, M.E., "A Small Deformation Thermo-Poromechanics Finite Element Model and its Application to Arterial Tissue Fusion," ASME Journal of Biomechanical Engineering. 140(3): 031007 (11 pages), 2018.

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Annals of Biomedical Engineering (2016): Strength and Persistence of Energy-Based Vessel Seals Rely on Tissue Water and Glycosaminoglycan Content

Anonymous — Fri, 21 Apr 2017 21:08:05 +0000

Annals of Biomedical Engineering (2016): Strength and Persistence of Energy-Based Vessel Seals Rely on Tissue Water and Glycosaminoglycan Content Anonymous (not verified) Fri, 04/21/2017 - 15:08

Abstract: Vessel ligation using energy-based surgical devices is steadily replacing conventional closure methods during minimally invasive and open procedures. In exploring the molecular nature of thermally-induced tissue bonds, novel applications for surgical resection and repair may be revealed. This work presents an analysis of the influence of unbound water and hydrophilic glycosaminoglycans on the formation and resilience of vascular seals via: (a) changes in pre-fusion tissue hydration, (b) the enzymatic digestion of glycosaminoglycans (GAGs) prior to fusion and (c) the rehydration of vascular seals following fusion. An 11% increase in pre-fusion unbound water led to an 84% rise in vascular seal strength. The digestion of GAGs prior to fusion led to increases of up to 82% in seal strength, while the rehydration of native and GAG-digested vascular seals decreased strengths by 41 and 44%, respectively. The effects of increased unbound water content prior to fusion combined with the effects of seal rehydration after fusion suggest that the heat-induced displacement of tissue water is a major contributor to tissue adhesion during energy-based vessel sealing. The effects of pre-fusion GAG-digestion on seal integrity indicate that GAGs are inhibitory to the bond formation process during thermal ligation. GAG digestion may allow for increased water transport and protein interaction during the fusion process, leading to the formation of stronger bonds. These findings provide insight into the physiochemical nature of the fusion bond, its potential for optimization in vascular closure and its application to novel strategies for vascular resection and repair.

Kramer, E.A., Cezo, J., Fankell, D. P., Taylor, K.D., Rentschler, M.E., Ferguson, V.L., "Strength and Persistence of Energy-Based Vessel Seals Rely on Tissue Water and Glycosaminoglycan Content," Annals of Biomedical Engineering. 44(11): 3421-3431, 2016.

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Annals of Biomedical Engineering (2016): A Novel Parameter for Predicting Arterial Fusion and Cutting in Finite Element Models

Anonymous — Fri, 21 Apr 2017 21:06:59 +0000

Annals of Biomedical Engineering (2016): A Novel Parameter for Predicting Arterial Fusion and Cutting in Finite Element Models Anonymous (not verified) Fri, 04/21/2017 - 15:06

Abstract: Current efforts to evaluate the performance of laparoscopic arterial fusion devices are limited to costly, time consuming, empirical studies. Thus, a finite element (FE) model, with the ability to predict device performance would improve device design and reduce development time and costs. This study introduces a model of the heat transfer through an artery during electrosurgical procedures that accounts for changes in thermal material properties due to water loss and temperature. Experiments then were conducted by applying a known heat and pressure to carefully sectioned pieces of porcine splenic arteries and measuring cut completeness. From this data, equations were developed to predict at which temperature and pressure arterial tissue is cut. These results were then incorporated into a fully coupled thermomechanical FE model with the ability to predict whole artery cutting. An additional experiment, performed to examine the accuracy of the model, showed that the model predicted complete artery cut results correctly in 28 of 32 tests. The predictive ability of this FE model opens a gateway to more advanced electrosurgical fusion devices and modeling techniques of electrosurgical procedures by allowing for faster, cheaper and more comprehensive device design.

Fankell, D., Kramer, E., Cezo, J., Ferguson, V.L., Taylor, K.D., Rentschler, M.E., "A Novel Parameter for Predicting Arterial Fusion and Cutting in Finite Element Models," Annals of Biomedical Engineering. 44(11): 3295-3306, 2016.

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ASME Journal of Biomechanical Engineering (2015): Bond Strength of Thermally Fused Vascular Tissue Varies with Apposition Force

Anonymous — Fri, 21 Apr 2017 21:05:28 +0000

ASME Journal of Biomechanical Engineering (2015): Bond Strength of Thermally Fused Vascular Tissue Varies with Apposition Force Anonymous (not verified) Fri, 04/21/2017 - 15:05

Abstract: Surgical tissue fusion devices ligate blood vessels using thermal energy and coaptation pressure, while the molecular mechanisms underlying tissue fusion remain unclear. This study characterizes the influence of apposition force during fusion on bond strength, tissue temperature, and seal morphology. Porcine splenic arteries were thermally fused at varying apposition forces (10–500 N). Maximum bond strengths were attained at 40 N of apposition force. Bonds formed between 10 and 50 N contained laminated medial layers; those formed above 50 N contained only adventitia. These findings suggest that commercial fusion devices operate at greater than optimal apposition forces, and that constituents of the tunica media may alter the adhesive mechanics of the fusion mechanism.

Anderson, N., Kramer, E., Cezo, J.D., Ferguson, V., Rentschler, M.E., "Bond Strength of Thermally Fused Vascular Tissue Varies with Apposition Force," ASME Journal of Biomechanical Engineering. 137(12): 121010 (6 pages), 2015.

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Surgical Endoscopy (2015): Tissue Storage Ex Vivo Significantly Increases Vascular Fusion Bursting Pressure

Anonymous — Fri, 21 Apr 2017 21:04:11 +0000

Surgical Endoscopy (2015): Tissue Storage Ex Vivo Significantly Increases Vascular Fusion Bursting Pressure Anonymous (not verified) Fri, 04/21/2017 - 15:04

Abstract: Harvested biological tissue is a common medium for surgical device assessment in a laboratory setting; this study aims to differentiate between surgical device performance in the clinical and laboratory environments prior to and following tissue storage. Vascular tissue fusion devices are sensitive to tissue-device temperature gradients, tissue pre-stretch in vivo and tissue water content, each of which can vary during tissue storage. In this study, we compare the results of tissue fusion prior to and following storage using a standardized bursting pressure protocol. Epigastric veins from seven porcine models were subject to identical bursting pressure protocols after fusion. One half of each vein was fused in vivo, harvested and immediately analyzed for burst pressure; the remainder was stored (0.9% Phosphate Buffered Saline, 24h, 4 °C) and then analyzed ex vivo. Histological slides were prepared for qualitative analysis of in versus ex vivo fusions. Bursting pressures of vessels fused ex vivo (514.7 ± 187.0 mmHg) were significantly greater than those of vessels fused in vivo (310 ± 127.7 mmHg, p = 2.06 E-10). Histological imaging of venous axial cross-sections indicated the lamination of adventitia and media layers ex vivo, whereas in vivo samples consisted only of adventitia. These findings suggest that the fusion of porcine venous tissue ex vivo may overestimate the clinical performance of fusion devices. Prior work has indicated that increased tissue hydration and the lamination of tissue layers both positively affect arterial fusion bursting pressures. The bursting pressure increase observed herein may therefore be due to storage-induced alterations in tissue composition and mechanics of the fusion interface. While harvested tissue provides an accessible medium for comparative study, the fusion of vascular tissue in vivo may avoid storage-induced biomechanical alterations and is likely a better indicator of fusion device performance in a clinical setting.

Cezo, J., Kramer, E., Schoen, J.A., Ferguson, V., Taylor, K., Rentschler, M.E., "Tissue Storage Ex Vivo Significantly Increases Vascular Fusion Bursting Pressure," Surgical Endoscopy. 29(7): 1999-2005, 2015.

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Journal of Mechanical Behavior of Biomedical Materials (2014): Evaluating Temperature and Duration in Arterial Tissue Fusion to Maximize Bond Strength

Anonymous — Fri, 21 Apr 2017 21:02:36 +0000

Journal of Mechanical Behavior of Biomedical Materials (2014): Evaluating Temperature and Duration in Arterial Tissue Fusion to Maximize Bond Strength Anonymous (not verified) Fri, 04/21/2017 - 15:02

Abstract: Tissue fusion is a growing area of medical research that enables mechanical closure of tissues without the need of foreign bodies such as sutures or staples. Utilizing heat and pressure applied for a specified time, a bond can be formed between adjacent tissues. The success or failure of tissue fusion is contingent upon the strength of the bond it creates between opposing tissues, yet little characterization has been done to measure the strength of this interface as a function of the input parameters, such as heat and pressure. Previous studies have examined the strength of tissue fusion using clinically relevant outcomes such as bursting pressure or tearing strength, but none have explored metrics more appropriate for determining the mechanics of the actual bond such as peel or shear strengths. The goal of this study is to establish methodology for T-peel and lap shear testing of fused tissues and measure the fusion bonding strength as a function of temperature and time using the ConMed Altrus^® laparoscopic thermal fusion device. Across five temperatures (120, 140, 150, 160, 170 °C) and four time durations (500, 1000, 1800, 3000 ms) the mean peeling strength, ultimate shear strength, and bursting pressure of fused porcine splenic arteries were measured. The shear strength increased with increasing temperature and time with an ultimate shear strength at 160 °C and 3000 ms equal to 290 ± 99 Pa. No trend was observed between the input parameters of time and applied temperature and the mean peeling force, although there were significant differences between groups. The bursting pressure increased significantly with increasing durations, but no trend was noted between temperature and bursting pressure. The shear strength data suggest there is some physical or chemical reaction which occurs in the tissue between 120 °C and 150 °C which provides a stronger bond. The shear and peel results also reveal that the fusion bond undergoes brittle failure. This study suggests that the tissue fusion bond is maximized at temperatures over 150 °C and at a time of 3000 ms using the ConMed Altrus^® and that input parameters can be tuned to optimize the strength of the bonded region.

Cezo, J.D., Passernig, A., Ferguson, V., Taylor, K., Rentschler, M.E., "Evaluating Temperature and Duration in Arterial Tissue Fusion to Maximize Bond Strength," Journal of Mechanical Behavior of Biomedical Materials. 30: 41-49, 2014.

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IEEE Transactions on Biomedical Engineering (2013): Temperature Measurement Methods during Direct Heat Arterial Tissue Fusion

Anonymous — Fri, 21 Apr 2017 20:59:40 +0000

IEEE Transactions on Biomedical Engineering (2013): Temperature Measurement Methods during Direct Heat Arterial Tissue Fusion Anonymous (not verified) Fri, 04/21/2017 - 14:59

Abstract: Fusion of biological tissues through direct and indirect heating is a growing area of medical research, yet there are still major gaps in understanding this procedure. Several companies have developed devices which fuse blood vessels, but little is known about the tissue's response to the stimuli. The need for accurate measurements of tissue behavior during tissue fusion is essential for the continued development and improvement of energy delivery devices. An experimental study was performed to measure the temperatures experienced during tissue fusion and the resulting burst pressure of the fused arteries. An array of thermocouples was placed in the lumen of a porcine splenic artery segment and sealed using a ConMed Altrus thermal fusion device. The temperatures within the tissue, in the device, and at the tissue-device interface were recorded. These measurements were then analyzed to calculate the temperature profile in the lumen of the artery. The temperature in the artery at the site of tissue fusion was measured to range from 142 to 163 °C using the ConMed Altrus. The corresponding burst pressure for arteries fused at this temperature was measured as 416 ± 79 mmHg. This study represents the first known experimental measurement of temperature at the site of vessel sealing found in the literature.

Cezo, J.D., Kramer, E., Taylor, K., Ferguson, V., Rentschler, M.E., "Temperature Measurement Methods during Direct Heat Arterial Tissue Fusion," IEEE Transactions on Biomedical Engineering. 60(9): 2552-2558, 2013.

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