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Research Papers

A New Laparoscopic Morcellator Using an Actuated Wire Mesh and Bag

[+] Author and Article Information
Alexander Isakov

Harvard University,
Department of Physics,
Cambridge, MA 02138
e-mail: isakov@fas.harvard.edu

Kimberly M. Murdaugh, William C. Burke, Sloan Zimmerman

Harvard University,
School of Engineering and Applied Sciences,
Cambridge, MA 02138

Ellen Roche, Conor J. Walsh

Harvard University,
School of Engineering and Applied Sciences,
Cambridge, MA 02138
Wyss Institute,
Boston, MA 02155

Donal Holland

Department of Mechanical and
Manufacturing Engineering,
Trinity College,
Dublin 2, Ireland

Jon I. Einarsson

Brigham and Women's Hospital,
Boston, MA 02115

Manuscript received March 21, 2013; final manuscript received December 16, 2013; published online January 15, 2014. Assoc. Editor: Carl A. Nelson.

J. Med. Devices 8(1), 011009 (Jan 15, 2014) (7 pages) Paper No: MED-13-1126; doi: 10.1115/1.4026294 History: Received March 21, 2013; Revised December 16, 2013

Laparoscopic morcellation is a technique used in gynecological surgeries such as hysterectomy and myomectomy to remove uteri and uterine fibroids (leiomyomas) through a small abdominal incision. Current morcellators use blades or bipolar energy to cut tissue into small pieces that are then removed through laparoscopic ports in a piecewise manner. These existing approaches have several limitations; (1) they are time consuming as the tissue must be manually moved over the devices during the cutting step and removal is piecewise, (2) they can lead to accidental damage to surrounding healthy tissue inside the body and (3) they do not provide safe containment of tissue during the morcellation process which can lead to seeding (spreading and regrowth) of benign or potentially cancerous tissue. This paper describes a laparoscopic morcellator that overcomes these limitations through a new design that is based on an enclosed, motor-actuated mesh that applies only an inward-directed cutting force to the tissue after it has been loaded into the protective mesh and bag. The deterministic design approach that led to this concept is presented along with the detailed electromechanical design. The prototype is tested on soft vegetables and an animal model to demonstrate successful morcellation and how the device would be compatible with current clinical practice. Results show that the time required to morcellate with the new device for a set of tests on animal tissue is relatively uniform across samples with widely varying parameters. Including tissue manipulation and extraction time, the new device is shown to have an improvement in terms of speed over current morcellators. The mean time for cutting animal tissue ranging from 100 g to 360 g was 30 s with small variations due to initial conditions. The time for cutting is expected to remain approximately constant as tissue size increases. There is also minimal risk of the protective bag ripping due to the inward-cutting action of the mesh, thereby potentially significantly reducing the risk of seeding during clinical procedures; thus, further increasing patient safety. Finally, this design may be applicable to other procedures involving removal of tissue in nongynecologic surgeries, such as full or partial kidney or spleen removal.

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References

Figures

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Fig. 1

Overview of the most common way morcellation is currently performed. Figure modified from Ref. [18]. (a) Rotocut G1 morcellator (Karl Storz GMBH, Tuttlingen, Germany). This morcellator is designed for laparoscopic hysterectomies and myomectomies. (b) Insertion directly into abdominal cavity. (c) Surgeon holds the tenaculum, grasping the tissue (shown on inset). (d) Cutting the tissue once it is pulled inside the sleeve.

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Fig. 2

Initial schematic rendering of three concepts in the mechanical debulking strategy. The first concept is the addition of a modified blade cover and a bag surrounding current morcellators. The second concept is rotary cutting along the edge of the tissue, with pieces falling into a bag. The third concept is linear radial cutting with a mesh, such that pieces fall into the surrounding bag.

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Fig. 3

First bench-level experiment for concept validation. (a) Hand-woven mesh made out of nylon fishing line, approximately 5 cm in width. Wires are connected outside of the cutting area for ease of pulling. (b) A cored apple with diameter much larger than a hole drilled in the wooden board; the board is the surface against which the cutting happens. (c) The apple is held in the mesh and force is applied upwards. (d) Fruit samples are reduced in size as the mesh is successfully pulled through.

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Fig. 4

(a) The mesh wires extend through the 1.5 cm hole in the plastic and attach to the clamp. The Instron pulls up while the plastic provides the normal force required for cutting the specimen. (b) The specimen is cut and the pieces are captured in a bag. The pieces are commensurate with the mesh spacing along at least one side.

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Fig. 5

Meshes with dimensions n × n (where n represents the number of wires per side) were used to cut potato (a) and kidney (b) samples. The meshes were made of 0.3 mm diameter steel wire. Data points represent the maximum force attained in pulling the mesh through the sample. The maximum cutting force increases approximately linearly in n.

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Fig. 6

A CAD rendering of a prototype with main system components identified

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Fig. 7

A professionally woven mesh (a) made of 22.7 kg tensile strength SpiderWire line. The diagonals of the squares are 1.5 cm in length. The threads extend 1.1 m away from the edges. A commercially available surgical bag shown with the deployer (TRS190SB2, Anchor Products) (b) was used to encase the mesh and prevent tissue spillage. Fig. 7(b) modified from Ref. [16].

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Fig. 8

A motor attachment turns the spool, winding the wires and retracting the mesh through the support rod

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Fig. 9

Jon Einarsson simulating the surgical procedure in a laboratory setting. (a) The bag-mesh combination is deployed. (b) Tissue (a kiwi) is inserted with the tenaculum. (c) The morcellator is inserted and the bag is closed. (d) Morcellated tissue falls into the bag.

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Fig. 10

The initial surgical setup with the porcine subject at the moment of insertion of the deployment mechanism (a). An endoscope is connected to the screen, and two trocars are placed for inserting other laparoscopic instruments. (b) A screen-capture of the endoscope, where the kidney is placed inside the mesh.

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Fig. 11

A large piece of tissue is left intact as it is compressed and pulled into the support rod directly (a). The remaining small pieces of kidney would fall into the bag (b). The variability in sizing is due to using professional meshes and hand-woven meshes on different runs. Pieces over 1 cm in greatest dimension are from hand-woven meshes.

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