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Research Papers

Bond Strength of Thermally Fused Vascular Tissue Varies With Apposition Force

[+] Author and Article Information
Nicholas S. Anderson

Department of Mechanical Engineering,
University of Colorado at Boulder,
427 UCB, 1111 Engineering Drive,
Boulder, CO 80309-0427

Eric A. Kramer

Department of Mechanical Engineering,
University of Colorado at Boulder,
427 UCB, 1111 Engineering Drive,
Boulder, CO 80309-0427
e-mail: eric.kramer@Colorado.edu

James D. Cezo

Department of Mechanical Engineering,
University of Colorado at Boulder,
427 UCB, 1111 Engineering Drive,
Boulder, CO 80309-0427
e-mail: James.Cezo@Colorado.edu

Virginia L. Ferguson

Associate Professor
Department of Mechanical Engineering,
BioFrontiers Institute,
Materials Science and Engineering Program,
University of Colorado at Boulder,
427 UCB, 1111 Engineering Drive,
Boulder, CO 80309-0427
e-mail: Virginia.Ferguson@Colorado.edu

Mark E. Rentschler

Assistant Professor
Department of Mechanical Engineering,
University of Colorado at Boulder,
427 UCB, 1111 Engineering Drive,
Boulder, CO 80309-0427
e-mail: Mark.Rentschler@Colorado.edu

1Corresponding author.

Manuscript received June 10, 2015; final manuscript received October 15, 2015; published online November 9, 2015. Assoc. Editor: David Corr.

J Biomech Eng 137(12), 121010 (Nov 09, 2015) (6 pages) Paper No: BIO-15-1293; doi: 10.1115/1.4031891 History: Received June 10, 2015; Revised October 15, 2015

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.

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Figures

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Fig. 1

Three-dimensional solid model of the custom loading fixture used in this study (left). Photograph of the fusion device during testing loaded onto the MTS Insight II platform (right).

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Fig. 2

Representative loading curve of a fusion with a prescribed force of 40 N. The points indicate events as follows: (A) onset of tissue compression, (B) PID controller compensates for overshoot, (C) heaters activate; tissue expands briefly, exerting pressure against the heater surfaces in response to the vaporization of tissue water, (D) PID controller compensates for decreased force exerted on the jaws and load cell due to volumetric tissue shrinkage and water loss, and (E) steady-state load achieved.

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Fig. 3

Box plots of the burst pressure data, normalized for vessel thickness, and grouped by apposition force during fusion (170 °C, 3 s duration). Median values are represented by horizontal lines, outliers (i.e., points outside of 1.5 times the interquartile range) are represented by crosses. Sample sizes of 14 per group were used for testing at 10–50 N; eight per group were used for testing at 100–500 N.

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Fig. 4

Mean thermocouple temperature in degree Celsius, plotted as a function of applied load and thermocouple position. Each section of the plot represents one thermocouple position, and each data point represents the mean temperature of five samples measured by that thermocouple at a particular load (defined by the key). All data are presented as mean± SD.

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Fig. 5

Hematoxylin and eosin (H&E) stained samples fused at applied loads of 20 N, 30 N, 40 N, and 100 N at 5× magnification. Note that the media (m) is included in the fusion region at 20 N and 30 N, begins to retract at 40 N, and is entirely absent at 100 N, where the fusion region is composed entirely of adventitia (a). The fusion region is denoted within each panel.

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