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Design Innovation Paper

Design, Analysis, and Experimental Evaluation of a Novel Three-Fingered Endoscopic Large-Organ Grasper

[+] Author and Article Information
Alireza Mirbagheri

NEF Postdoctoral Fellow
Robotic Surgery Lab.,
Research Centre of Biomedical Technology and Robotics,
Tehran University of Medical Sciences,
Tehran 1419733141, Iran
e-mail: mirbagheri@ieee.org

Farzam Farahmand

Professor of Biomechanics
School of Mechanical Engineering,
Sharif University of Technology and Research Centre of Biomedical Technology and Robotics,
Tehran University of Medical Sciences,
Tehran 11155-9567, Iran
e-mail: farahmand@sharif.edu

1Corresponding author.

Manuscript received September 23, 2011; final manuscript received January 2, 2013; published online June 24, 2013. Assoc. Editor: Foster B. Stulen.

J. Med. Devices 7(2), 025001 (Jun 24, 2013) (6 pages) Paper No: MED-11-1087; doi: 10.1115/1.4023704 History: Received September 23, 2011; Revised January 02, 2013

The currently available laparoscopic instruments are unable to manipulate and grasp the large intra-abdominal organs, such as spleen and kidney, with sufficient stability and safety. This paper describes a novel three-fingered endoscopic instrument, based on parallelogram mechanism, which can fully constrain the large organs and provide an effective grasping function. We first evaluated the efficacy of the design using a 3D model and finite element analysis. Then, a fully functional prototype was fabricated for experimental evaluations, including force propagation and pull force limitation characteristics. Finally, the instrument's capability for effective grasping was investigated on animal specimens in in vitro and in vivo examinations. The results of the force propagation analysis indicated a high amplification ratio of more than 1.2 for the actuating force when grasping large organs. The pull force experiments on a sheep heart specimen revealed a nearly linear relationship between the actuating force and the limit of the pulling force that could be attained without slippage. The resulting pinch force, however, was found to be injurious if the actuating force exceeded a limit of 8.6 N. The in vitro and in vivo examinations of the instrument indicated its capability to pass through a standard 10-mm trocar to enter the abdomen, open its fingers to a diameter of about 80 mm, and grasp and manipulate organs with different sizes, shapes, and properties. With further developments, the proposed design is expected to provide a practical and feasible solution for grasping of large organs during endoscopic operations. However, more preclinical examinations are needed to evaluate the potential risks of using rigid jaws against injury-prone soft organs.

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Figures

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Fig. 1

The parallelogram mechanism of the designed instrument

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Fig. 2

The closed (left) and opened (right) configurations of the designed instrument

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Fig. 3

Finite element analysis of the mechanical components of the designed instrument

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Fig. 4

The prototype of the grasper in closed (a) and opened (b) configurations and during grasping of a relatively rigid elliptical object through a 10-mm-diameter port in a phantom test ((c)–(e))

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Fig. 5

The experimental setup to determine the relationship between the actuating force at the handle and the pinch force at a jaw of the instrument

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Fig. 6

The experimental setup to determine the pull force limit for effective grasping of a sheep heart with different actuating forces

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Fig. 7

The analytical and experimental results for the actuating force–pinch force relationship of the designed instrument at three different grasping configurations of small (θ = 30 deg), middle (θ = 45 deg), and large size (θ = 60 deg) body organs

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Fig. 8

The hysteresis of force propagation from instrument handle to its jaws at θ = 45 deg

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Fig. 9

The limit of the pulling force on the grasped organ versus the actuating forces at the instrument handle for effective grasping of a sheep heart specimen

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Fig. 10

The in vivo tests to evaluate the prototype's capability for effective and safe grasping of the intra-abdominal organs of a dog specimen: inserting into the abdomen through a 10-mm trocar (a); opening to grasp the liver (b); grasping the liver (c); manipulating the liver (d); grasping and pulling up the gall bladder (e) and the urinary bladder (f)

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