Procedia Engineering 132 ( 2015 ) 1014 1020 [629913]

Procedia Engineering 132 ( 2015 ) 1014 – 1020
1877-7058 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the Scientific Committee of MESIC 2015
doi: 10.1016/j.proeng.2015.12.590 ScienceDirectAvailable online at www.sciencedirect.com
The Man ufacturing Engineering Society International Conference, MESIC 2015
Guide design of precision tool handle based on ergonomics criteria
using parametric CAD software
A.G. Gonzáleza,*, J. García Sanz-Calcedoa, O. Lópeza, D.R. Salgadob, I. Camberob, J.M.
Herrerab
aDepartment of Mechanical, Energetic and Materials Engineering, University of Extremadura. Avda Sta. Teresa 38, 06800, Mérida Sp ain.
bDepartment of Mechanical, Energetic and Materials Engineering, University of Extremadura. Avda. Elvas s/n. 06010, Badajoz, Spai n.
Abstract
This work shows an analysis of the design of commercial in struments used in laparoscopic surgery mainly the used mate rials. In
a f
irst phase the study has carried out the current state of the a rt of these instruments, based mainly on bibliographical refe rences
and in consultations to the Jesús Usón Minimally Invasiv e Surgery Centre and the Institute of Biomechanics of Va lencia.
In a second phase, a tweezer was been modeled and developed wi th the software CAD 3D Soli dWorks, and later the design has
been evaluated, modifying lightly its geometry and materials for reducing the weight. It is important to emphasize the
possibilities that SolidWorks offers for th e optimization of the design of instruments of laparoscopic surgery. Finally, the st udy
has revealed that with some geometric modifications, that do not modify the use of these instruments, and with some changes in
the used materials, it is possible to reduce the weig ht and facilitates the employment to the user.

© 2016 The Authors. Published by Elsevier Ltd .
Peer-review under responsibility of the Scientific Committee of MESIC 2015 .
Keywords: Tool handle design; ergonomic criteria; CAD/CAM.
1. Introduction
The widespread and increasing use of laparoscopic surgery has highlighted specific injuries related to the use of
instruments and special techniques developed for these procedures.

* Corresponding author. Tel.: +34924289300 fax: +34924301212
E-mail address: [anonimizat] © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer
-review under responsibility of the Scientific Committee of MESIC 2015

1015 A.G. González et al. / Procedia Engineering 132 ( 2015 ) 1014 – 1020
Many companies are developing tools for minimally invasive surgery (MIS) by expanding the selection of
devices available to surgeons. Although the techniques have reached a relatively high level of development, the
ergonomic features of these instrume nts are still weak, as demonstrated in works [1 -6]. Surgeons often complain of
pressu
re as well as pain and fatigue in hands and lower limb jo ints [1, 4, 5, 6]. These injuries can be attributed to the
repetitive and prolonged use of some ergonomic instrume nts. The existing general ergonomic guidelines for the
design of hand tools are not sufficiently specific, being therefore inadequate fo r laparoscopic instrument design [5,
7].
In this study the goal is to improve the use of laparos co pic surgery pliers, as in the above mentioned works,
modifyi ng its geometry according to the user’s ergonomic data, and generating from these data a parametric design
apparatus which allows optimal design based on the size of the surgeon's hand. For this we have worked with a 3D
model of the commercial clip generated in SolidWorks, so as further analysis using rapid prototyping techniques in
order to validate the results in a short time while enabling this validation to be performed on a real test on the
designed instrumental during surgery.

2. Objectives

The aim of this work is to establish a guide based on biomechanical and ergonomic criteria that allow the
parametric optimal design of laparoscopic surgery pliers with regard to the size of the surgeon's hand on the basis of
the conclusions and ergonomic recommendations about the current state of the equipment.
These recommendations are based on th e detection and identificat ion of possible improper ergonomic conditions,
both obtained from instrumental analysis (mechanical, us e, etc.), Surgeons (through questionnaires) and studies
based on references, publications an d consultations in specialized journals.

3. Methodology

The methodology proposed in this paper is based on b oth the documentation analysis of anthropometric
ergonomics and that of laparoscopic surgery. The results are recorded in the tables of this work.
First we recorded the main results obtained in the phase of "existing instrumental documentary research." The
following are the main ergonomic requirements to be fulfilled by the instrumental. Relying for that purpose on modeling business laparoscopic surgery pliers (see Fig. 1) in SolidWorks, to further evaluate the design of the clip
from its rapid prototyping.

Fig. 1: Laparoscopic needle holders

1016 A.G. González et al. / Procedia Engineering 132 ( 2015 ) 1014 – 1020
Currently, there are many types of laparoscopic instruments; Figure 2 shows the different types of handles for the
v
arious functions required. Axial handles, two ring handles, th ree or even four fingers, and some more innovative
designs such as those in the pictures below.

Fig. 2: (a) Instruments handles; (b) precision grip; (c) grip strength .
Different types of classification have been established he re . The first one regarding the number of applications.
According to this classification we ca n distinguish between reusable, semi -reusable and disposable instrumental.
Studies carried out have shown [8], that reusable laparos co pic instruments substantially reduce the cost of
laparoscopic surgery, without compromising safety of p ati ents and medical personnel. Initial acquisition costs are
quickly amort ized and further depreciated with every use. In additio n , the causes that led to a hospital to change the
type of instruments were assessed, concluding that the hospitals did so because they improved the quality of
performance in surgery. In this study we can conclude that th e priority of surgeons is to find quality instruments that
will allow good for a performance in laparoscopic surgery. A second classification of laparoscopic instruments has
been carried out according to their functional characteristics [5]. These authors distinguish four groups of
instr
uments:
x GROUP I: Active Tissue Handling Instrumental (dissecting f orceps, grasping forceps, scissors, needle holder and
suture forceps);
x GROUP II: Electro Surgery Instrumental;
x GROUP III: Instruments for Sutures and the division of ti ssues (staplers, clip app licators, automatic sutures);
x GROUP IV: Suction and irrigation tubes.
This work focuses on the first instrumental group. We ca n distinguish, within this group there are three parts of
each instrument: Handle, pod and insert, the base of our study being the handle.
A study [5] conducted to determine the percentage of use of these types of handles associated with the different
types of functions, led to the most outstanding results such as follows and as reflected in Figure 3:
x 71% of dissecting forceps, grasping forc e ps and scissors use handles Type 1.
x 56% of Type 4 handles are used to su ture needle holders and forceps.

1017 A.G. González et al. / Procedia Engineering 132 ( 2015 ) 1014 – 1020
Fig. 3: Percentages of the use of handle types of instruments of Group I.
To make a good ergonomic design, the adaptation must take into account the size ranges between 5 and 95
percentile of the population. These dimensions should also include that some space for the gloves.
For the design of instruments, as well as hand tools, basic a nthropometric parameter s to consider are those
relating the dimensions of the hand. Then specify the main di mensions to be considered in the design of the handle
of the instrument (see Fig. 4):
x Length of the hand (a).
x Length of the palm (b).
x Width of hand at the metacarpal (c).
x Length of the index finger (d).
x Width of index finger, proximal (e).
x Width of index finger, distal (f).
x Width of the thumb (g).

a) b) c) d) e)
Fig. 4: Main dimensions in the design of the handle of the instruments.
Various workers have studied the design of handles of lap aroscopic surgical instruments, analysing their
ergonomics [3, 9, 10, 11), functionality [12, 13], and the de crease in the comfort and muscle activity that result from

1018 A.G. González et al. / Procedia Engineering 132 ( 2015 ) 1014 – 1020
their use [14]. González et al. [13] in his study showed that there is a relationship between the sizes of the length of
th
e palm (see Fig. 4b) with the optimum diameter instrumental grabs.
Table 1 shows the anthropometric hand (in mm) of bot h men and women as a whole, which are related to the
design
of the handle and are the variables that influence the parameters of our work.
Table 1. Anthropometric data for the hand of the Spanish population (Carmon [15], INSHT [16])
Nș Refer.
ISO (7250:1996) Designation Sample
Size Mean SD Sampl e
Size Mean SD Sample
Size Mean SD
Measures of specific segments of the body (mm)
Type population Male Female Joint
1 Hand Length 1,126 188.18 9.79 593 172.99 8.72 1,719 182.94 11.88
2 Palm Length 1,126 107.00 6.00 593 97 5 1,719
3 Width of hand at
the metacarpal 1,127 89.30 5.99 592 77.65 0.193 1,719 85.29 7.86
4 Length of the
index finger 898 73.89 4.64 480 68.46 4.01 1,378 72 5.13
5 Width of hand at
the metacarpal 1,130 21 1.5 592 18.11 1.54 1,722 19.88 1.99

To establish the difference between men and women in the design of instruments, a previous study was made on
some clay handles, taking data from the diameter, angle, lengt h, once the different subjects (men and women) had
adapted the handles to their hands. This handle (shape) was generated with Solidworks and developed using rapid
prototyping techniques and its design was tested and valeted using a trial an error methodology. The final shape of
the handle was obtained after a trial -error design process. The evolution of th e shape of the handle was carried out in
the ERGOLAP Project [17]. For this purpose, different tests were used to ob tain information: analysis of the EMG
signals corresponding to the activity of va rious muscles with CyberGlove, analysis of the signals from goniometers;
and th
e opinion of surgeons using questionnaires and interviews. Figure 5 shows how these tests were conducted.

Fig. 5: Tests made for the determination of the handle shape.
4. Resul ts
Below is a comparative table of the criteria Van Veele n et al. [5] and NIOSH [18] have been obtained for
dissecting forceps and the results based on the study. In carrying out the table also they took into account the criteria
for ergonomic design obtained in Ergolap project [17].

1019 A.G. González et al. / Procedia Engineering 132 ( 2015 ) 1014 – 1020
Table 2. Comparative table of the criteria Van Veelen et al. [5] and NIOSH [18]
Laparoscopic needle holders
Criteria by Van Veelen Study criteria

1 The angle between handle and the shaft should be between 40ș
and 50ș Unchanged Unchanged
2 Gripping opening must be between 60 and 80 mm. 70-80 mm 60-70 mm
3 For in -line handles: the length of the grip handle may not be
l
onger than 170 mm. Unchanged 160 mm
4 The handle of the needle holder must have a minimum width
of 10 mm to avoid pressure areas. Axial: > 10 mm
Circular:
Diameter between
4
8 and 57 mm Axial: > 10 mm
Circular:
Diameter between
4
6 and 55 mm
5 If the handle contains fingerings, the dimensions of these
fingerings must be length 30 mm, width 24 mm. Unchanged Length: 30 mm
Width: 21 mm

4. Conclusions

The recommended range for the angle does not chang e in relation to the criteria applied by Van Veelen [5]. Yes
w
e can see variations in the others. In the parameter that re fers to the opening range, with between 70 to 80 mm for
men and 60 to 70 mm for women. With regards to the maximum length parameter, the range of the man does not
change, but that of the woman does, who may have a maximum size up to 150 mm. Regarding the width in the axial
handles the width does not change but in regard to the circular type being the range of 48 to 57 mm in men and from
46 to 55 mm in the female, data matching with the r esults published in similar studies [9, 12].
There are some general conclusions for th is study. In theory, create an infinitely variable prototype would be the
ideal solution to suit individual prefer ences based on their anthropometric measurements. However, in practice it
would be impracticable, but you can reduce the number of those parameters that have been presented in this study with those that could approach the ideal case. It would be interesting if future studies could build physical prototypes based on the results [14] so we can verify the suitability of them.
Acknowledgements
The authors thank the CCMI (Center for Minimally In vasiv
e Surgery Cáceres) and the IBV (Institute of
Biomechanics of Valencia,) for their support, to provide baseline da ta for conducting this work, the Ministry of
Edu
cation and Science through funding gr anted in the reference project DPI2007 -65902 -C03-03 and trough funding
of
the Government of Extremadura – Counseling of Economy, Trade and I n novation and the European Regional
Develo pment Fund (ERDF).
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