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Research Papers

A Laparoscopic Morcellator Redesign to Constrain Tissue Using Integrated Gripping Teeth

[+] Author and Article Information
E. A. Arkenbout

Biomechanical Engineering Department,
Faculty of Mechanical, Maritime, and
Materials Engineering,
Delft University of Technology,
Mekelweg 2,
Delft 2628 CD, The Netherlands
e-mail: e.a.arkenbout@tudelft.nl

L. van den Haak

Department of Gynecology,
Leiden University Medical Center,
Albinusdreef 2,
Leiden 2333 ZA, The Netherlands
e-mail: L.van_den_Haak@lumc.nl

M. Penning

Life Science and Technology Department,
Faculty of Applied Sciences,
Lorentzweg 1,
Delft 2628 CJ, The Netherlands
e-mail: maxime_penning@hotmail.com

E. Rog

Maritime Transport Technology Department,
Faculty of Mechanical, Maritime, and
Materials Engineering,
Delft University of Technology,
Mekelweg 2,
Delft 2628 CD, The Netherlands
e-mail: ellemijnrog@gmail.com

A. Vierwind

Life Science and Technology Department,
Faculty of Applied Sciences,
Lorentzweg 1,
Delft 2628 CJ, The Netherlands
e-mail: amandavierwind@hotmail.com

L. E. van Cappelle

Faculty of Mechanical, Maritime, and
Materials Engineering,
Delft University of Technology,
Mekelweg 2,
Delft 2628 CD, The Netherlands
e-mail: l.e.vancappelle@gmail.com

F. W. Jansen

Department of Gynecology,
Leiden University Medical Center,
Albinusdreef 2,
Leiden 2333 ZA, The Netherlands
e-mail: f.w.jansen@lumc.nl

J. C. F. de Winter

Biomechanical Engineering Department,
Faculty of Mechanical, Maritime, and
Materials Engineering,
Delft University of Technology,
Mekelweg 2,
Delft 2628 CD, The Netherlands
e-mail: J.C.F.deWinter@tudelft.nl

1Corresponding author.

Manuscript received March 17, 2016; final manuscript received September 19, 2016; published online December 21, 2016. Assoc. Editor: Carl Nelson.

J. Med. Devices 11(1), 011005 (Dec 21, 2016) (13 pages) Paper No: MED-16-1195; doi: 10.1115/1.4034882 History: Received March 17, 2016; Revised September 19, 2016

Laparoscopic hysterectomy is a procedure that involves the removal of the uterus through an abdominal keyhole incision. Morcellators have been specifically designed for this task, but their use has been discouraged by the food and drug administration (FDA) since November 2014 because of risks of cancerous tissue spread. The use of laparoscopic bags to catch and contain tissue debris has been suggested, but this does not solve the root cause of tissue spread. The fundamental problem lies in the tendency of the tissue mass outside the morcellation tube to rotate along with the cutting blade, causing tissue to be spread through the abdomen. This paper presents a bio-inspired concept that constrains the tissue mass in the advent of its rotation in order to improve the overall morcellation efficacy and reduce tissue spread. A design of gripping teeth integrated into the inner diameter of the morcellation tube is proposed. Various tooth geometries were developed and evaluated through an iterative process in order to maximize the gripping forces of these teeth. The maximum gripping force was determined through the measurement of force–displacement curves during the gripping of gelatin and bovine tissue samples. The results indicate that a tooth ring with a diameter of 15 mm can provide a torque resistance of 1.9 Ncm. Finally, a full morcellation instrument concept design is provided.

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Figures

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Fig. 1

Representation of the tissue mass spinning problem underlying power morcellators. (a) Initiation of morcellation where tissue is pulled into the morcellation tube (Fpull) and a tissue strip is being cut properly. (b) Midway through morcellating a tissue strip, where the strip has come to be of such length that twisting of the strip inside the tube occurs. This results in a (possible) torque (FT) of the tissue mass, induced by the rotating cutting blade, spinning the tissue. (c) Morcellation failure due to rupturing of the (twisted) tissue strip inside the tube. The tissue mass is free to follow the torque FT as well as disconnect from the morcellation tube (Fz), resulting in a combined force vector Fc, indicating the direction to where the tissue mass falls or is flung. Note: force vectors not to scale.

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Fig. 2

Patent morcellator designs that engage and constrain the main tissue mass during morcellation. (a) Patent US20150073224A1 [68], (b) patent US20130090642A1 [70], and (c) EP0706781A2 [54]. Images cropped and component numbers removed from original patents.

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Fig. 3

(a) Lamprey. Image edited to only show the mouth [93], (b) lamprey inspired morcellation instrument tip, having integrated teeth for tissue traction, and (c) design of a single teeth ring. Dimensions are in millimeters.

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Fig. 4

Flowchart of the sequence of measurements performed, where at each measurement a force–displacement curve was generated. In measurement sessions 1–4, porcine gelatin samples were pulled over the indicated teeth in the directions FT, FC, or FZ (Fig. 1), using the test setup shown in Fig. 5. In measurement sessions 5 and 6, animal tissue samples were pulled in directions FZ and FT, in contact with the teeth ring, using the test setup shown in Fig. 8.

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Fig. 5

(a) Three-dimensional view of the gelatin and teeth test setup, (b) side view of the setup, and (c) example of the teeth that have been evaluated. A gelatin sample (small block) was placed near the teeth, which were placed under an angle. Pulling the sample in the force directions FZ, FT, and FC, (as also shown in Fig. 1) evaluated the gripping force the teeth had on the sample in that specific direction. Force–displacement measurements were performed with a tensile tester.

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Fig. 6

First (top) and second (bottom) range of teeth evaluated in measurement session 1 and sessions 2–4, respectively

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Fig. 7

Prototyped steel teeth ring, using tooth geometry J (Fig. 10, bottom), 2.0 mm height, 1.4 mm width, 0.3 mm spacing between teeth, and 45 deg inward angle. The ring has 21 teeth.

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Fig. 8

(a) Three-dimensional view of the bovine tissue and teeth test setup, (b) close-up of tissue sample clamped and subjected to forces FZ or FT while in contact with the teeth ring, and (c) top view of the setup. A tissue sample is placed in contact with the teeth, which is mounted at the end of the morcellation tube. Pulling or rotating the sample in the force directions FZ or FT, as also shown in Fig. 1, evaluates the grip the teeth have on the sample in that specific direction. Force–displacement measurements were performed with a tensile tester.

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Fig. 9

(a) Characteristic sample measurement (teeth range 1, teeth type D, measurement session 1). The maximum grip force on the gelatin sample is indicated by Fmax. (b–e) Results of measurement sessions 1 through 4. All results are presented as mean ± SD gripping force. (b) Measurement session 1: force generated by various tooth geometries in force direction FZ. (c) Measurement session 2: force generated by various geometry and size teeth in force direction FC. (d) Measurement session 3: force generated by teeth types F and J in force directions FZ, FT and FC. (e) Measurement session 4: force generated by tooth geometry J in force directions FC and inverse of FZ (i.e., −FZ), each for three different angles of the teeth with respect to the horizontal surface.

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Fig. 10

Results of measurement sessions 5 and 6. (a) Mean ± SD maximum teeth gripping force in force directions Fz and Fc (translations and rotations plot, respectively). Three measurement trials were performed per tissue strip, and results are group per trial number. (b) Results of measurement sessions 5 and 6. Mean ± SD of the maximum teeth gripping force pulled along with and against the pointing direction of the teeth, respectively.

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Fig. 11

Concept design of a generic morcellator combined with an add-on module providing a passive inner morcellation tube with teeth rings that hook into the tissue strip at the occurrence of tissue mass spinning. (a) The add-on module connects to the morcellator through a clamping mechanism at the back-end. (a) Three-dimensional zoom-in on instrument tip, (b) full 3D model, (c) back view of model and (d) front view and side view with cross section of instrument tip.

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