applied sciences

Article An Ergonomic Customized-Tool Handle for Precision Tools using Additive Manufacturing: A Case Study

Alfonso González González 1,* ID , David Rodríguez Salgado 2, Lorenzo García Moruno 3 ID and Alonso Sánchez Ríos 3 ID 1 Campus of Mérida City, Department of Mechanical, Energy, and Materials , University of Extremadura, 06800 Mérida, Spain 2 Campus of Badajoz City, Department of Mechanical, Energy, and Materials Engineering, University of Extremadura, 06071 Badajoz, Spain; [email protected] 3 Department of Graphical Expression, University of Extremadura, 06800 Mérida, Spain; [email protected] (L.G.M.); [email protected] (A.S.R.) * Correspondence: [email protected]; Tel.: +34-924-28-93-00

 Received: 12 June 2018; Accepted: 18 July 2018; Published: 22 July 2018 

Abstract: A study was carried out with 135 surgeons to obtain a surgical laparoscopic grasper handle design that adapts to the size of each surgeon’s hand, in a functionally appropriate way, and has the sufficient ergonomics to avoid generating the problems detected nowadays. The main conclusion of the work is the practical 3D obtained for a laparoscopic surgical graspers handle that is scalable to fit each particular surgeon's hand size. In addition, it has been possible to determine that the anthropometric measure of the surgeon's hand defined as Palm Length Measured (PLM) allows the design of the 3D parametric model of the surgical handle to be conveniently scaled. The results show that both additive manufacturing and the application of ergonomics criterion provide an efficient method for the custom design and manufacture of this type of specialised tool, with potential application in other sectors.

Keywords: parametric design; anthropometric; custom handle design; rapid prototyping; 3D CAD

1. Introduction Universal object try to fit all users using the criterion known as “” [1]. This criterion is included in the “” guide, which in turn lists the “7 principles of universal design” [2]. One of these principles is to facilitate “flexibility in use”. The proposal by Mace et al. [2] was further developed by Story et al. [3], in order to make the use of products designed for the greatest number of people, accessible [4]. To comply with this principle, hand tools in particular should satisfy a number of guidelines in their design. These include overcoming such obstacles as age, sex, dexterity, motor skills, etc., and whether the user is right- or left-handed, so that the handles can be adapted to different hand sizes and shapes. One of the fundamental problems in hand tool design is in trying to optimize the dimensions of the tool relative to the hand anthropometry. Another fundamental challenge is faced when trying to make sure that the shape and dimensions of the design are consistent with the type and specific functionality of each instrument type [5]. For the instruments used in laparoscopic surgery, Alleblas et al. [6] notes the need to assess expert opinions regarding the current designs of their handles. This is done in order to determine surgeons’ needs and expectations with respect to the laparoscopic instruments they currently use and the possibility of the future implementation of haptic feedback in their design. Other studies, such as that of Stoklasek et al. [7] on tools used for the assembly of electric motors, show that while

Appl. Sci. 2018, 8, 1200; doi:10.3390/app8071200 www.mdpi.com/journal/applsci Appl. Sci. 2018, 8, 1200 2 of 13 requirements for the functional parts of the tool (duration, making it impossible to damage the motor’s installation, etc.) were taken into account in the design, ergonomic requirements for the gripping area Appl. Sci. 2018, 8, x FOR PEER REVIEW 2 of 14 of the tool were not. Prolonged use of tools with poor ergonomic design was shown to cause discomfort resulting inmotors, numbness show that or paraesthesia while requirements (“pins for and the functional needles”) parts in the of workers’the tool (duration, fingers. making it Handimpossible size is to a damage determining the motor factor’s installation, in how etc.) precision were taken tools, into account in particular in the design, laparoscopic ergonomic graspers, requirements for the gripping area of the tool were not. Prolonged use of tools with poor ergonomic are used [8design]. Small-handed was shown to surgeonscause discomfort experience resulting more in numbness grip problems or paraesthesia than those (“pins withand needles large” hands,) in and are forced to holdthe workers the handle’ fingers. differently from what was originally considered in its design phase [8]. Current surgical laparoscopicHand size tools is a determinin usuallyg come factor inin how a standard precision size, tools, and in particular the surgeon laparoscopic must graspers, adapt accordingly are by holding andused gripping [8]. Small them-handed in surgeons certain ways,experience which more a grip priori problems depend than on those the sizewith oflarge his hands, or her and hand. are forced to hold the handle differently from what was originally considered in its design phase [8]. TheCurrent conventional surgical laparoscopic tools surgery usually come graspers in a standard shown size, in Figureand the1 surgeon incorporate must adapt a pistol grip mechanismaccordingly with finger by holding rings, and and gripping a mechanism them in certain that ways, allows which full a rotationpriori depend of the on tipthe size of the of his shaft (upper part of theor graspers).her hand. The three images in the figure show different forms of gripping the instrument depending onThe the conventional size of the laparoscopic user’s hand. surgery In the graspers case of shown Figure in Figure1a, a surgeon 1 incorporate with a a pistol small grip hand holds mechanism with finger rings, and a mechanism that allows full rotation of the tip of the shaft (upper the handlepart without of the graspers). being ableThe three to encompass images in the allfigure of theshow instrument’s different forms graspingof gripping elements.the instrument In Figure1b, the oppositedepending case is on revealed: the size of Athe surgeon user’s hand. with In the a large case of hand Figure is 1a, unable a surgeon to make with a simultaneoussmall hand holds use of most of those elements,the handle without and grips being the able handle to encompass in acompletely all of the instrument different’s grasping way. elements. The ideal In gripFigure would 1b, be that shown inthe Figure opposite1c,in case which is revealed: all the A grasping surgeon with elements a large hand fit the is sizeunable of to the make hand simultaneous perfectly. use It isof important most of those elements, and grips the handle in a completely different way. The ideal grip would be to note thatthat the shown grips in representedFigure 1c, in which in Figure all the1 graspingare not arbitrary,elements fit but the rathersize of the reflect hand realperfectly. situations It is brought about whenimpo thertant size to ofnote the that hand the grips and therepresented dimensions in Figure of the 1 are handle not arbitrary, do not but correspond. rather reflect These real different grips weresituations observed brought in the about Centro when the de size Cirug of theía de hand M í andnima the Invasi dimensionsón Jes of ú thes Us handleón (CCMIJU) do not which collaboratedcorrespond. in the developmentThese different grips of the were present observed study. in the Centro de Cirugía de Mínima Invasión Jesús Usón (CCMIJU) which collaborated in the development of the present study.

(a) (b) (c)

Figure 1. Different forms of gripping the surgical laparoscopic tool according to the surgeon’s hand Figure 1. size.Different The most forms irregular of grippingones for this the grip surgical are the first laparoscopic two (a,b). These tool usually according appear towhen the the surgeon’s size hand size. The mostof the tool irregular is not adapted ones for to the this size grip of the are surgeon the first’s hand. two The (a, bthird). These (c) is the usually most common, appear and when the the size of the tool isinformation not adapted provided to the directly size by of th thee surgeons surgeon’s indicate hand. that it The caused third the least (c) is injuries. the most common, and the information provided directly by the surgeons indicate that it caused the least injuries. At present, as various recent studies have observed [9–12], the instruments used in laparoscopic surgery are characterized by being of a single size (as mentioned above) and with little ergonomy in At present,their design. as various The single recent size of studies minimally have invasive observed surgery [ 9(MIS)–12], instruments the instruments means that used surgeons in laparoscopic surgery arehave characterized to adapt to the by instruments, being of a and single different size surgeons (as mentioned show different above) patterns and with of adaptation little ergonomy in depending on their hand size. In spite of this adaptation, neither small- nor large-handed surgeons their design.can find The a single comfortable size of zone minimally to grip and invasive manipulate surgery laparoscopic (MIS) instrumentsgrasping tools. meansThis is especially that surgeons have to adapt totrue the for instruments, actioning the opening and different and closing surgeons mechanism show of the differentgrasper. This patterns problem ofhas adaptation been broughtdepending on their handto light size. in various In spite studies of thissuch adaptation,as that of Berguer neither and Hreljac small- [5] nor, who large-handed surveyed users surgeons of these can find a comfortableinstruments, zone finding to grip that and both manipulate those with large laparoscopic hands and those grasping with small tools. hands This found is them especially hard true for to use. actioning theGiven opening this situation, and closing several mechanism research papers of thehave grasper. been published This problemin recent ye hasars analysing been brought the to light in variouscorrespondence studies such that as mustthat ofexist Berguer between anda user Hreljac’s anthropometric [5], who characteristics surveyed users and the of theseprecision instruments, finding thatinstruments both those they use, with which large need hands to be ergonomically and those with adapted small to the hands user’s hand. found Sancho them-Bru hard et al. to[13] use. Givenused this a situation,biomechanical several model research of the hand papers to study have the been appropriate published diameter in recent of a handle years with analysing the cylindrical grip for men and women. Other studies indicate that the shape of the handle should be correspondence that must exist between a user’s anthropometric characteristics and the precision instruments they use, which need to be ergonomically adapted to the user’s hand. Sancho-Bru et al. [13] used a biomechanical model of the hand to study the appropriate diameter of a handle with cylindrical grip for men and women. Other studies indicate that the shape of the handle should be designed to optimize the performance of the tasks in which the tool is to be used [9], maximize the ease of use and contact area between the hand and the handle [10,14], and to distribute pressure so as to minimize Appl. Sci. 2018, 8, 1200 3 of 13 discomfort [11,12]. Other anthropometric studies have had the aim of determining laparoscopic surgery instrument dimensions that adapt to different hand sizes [8,15–18]. However, it should be noted that these last works defined three or four sizes for the handle, but listed no criterion for the design of a handle customized for each surgeon. There are many ergonomic directives and guides in the literature for the design of everyday products. Examples include “Ergonomics and Design. A Reference Guide” [19] for the development of products to improve workplace environments and the “Office Ergonomics. Guidelines for Preventing Musculoskeletal Injuries” [20] which gives a series of guidelines to make working with computers more comfortable. A few even appear in the healthcare sector, such as “Ergonomics Guidelines” [21] for surgical instruments, although none specifically discuss laparoscopic graspers. Most of these ergonomic design guides are too generic for specific applications, and there is a clear need to develop more specific guidelines for the ergonomic design of precision MIS tools [6,22–25]. The ever more widespread application of MIS has brought to the forefront the problem of specific injuries related to the use of laparoscopic tools. Although the techniques of MIS have already attained a relatively high of development, the ergonomic characteristics of the tools it uses are still deficient [17,26–31]. Surgeons frequently complain of pressure, pain, and fatigue in their hands while using these instruments, which frequently result in lesions [26,28,29,32–37]. According to Trejo et al. [36], these lesions can be attributed to the repetitive and prolonged use of unergonomic instruments. Park et al. [37] found that 87% of surgeons who regularly perform laparoscopic surgery suffer lesions, and that the main cause is this lack of ergonomy. Therefore several firms in the medical sector, such as Dimeda-Surgical Instruments and WISAP Medical Technology GmbH in Germany, Medtronic in the US, and Endomexico in Mexico, have been working to overcome the problems with the design of MIS tools. In the circumstances, the main purpose of this paper was to design an ergonomic handle for laparoscopic surgery tools that adapted to each surgeon based on the anthropometry of their hands. The basis would be a parametric design of the handle that includes all the specifications needed for it to be more ergonomic and functional than current handles. The work involved the participation of a total of 135 surgeons, and most of it was carried out in coordination with the CCMIJU.

2. Methods

2.1. Introduction The experimental phase of this work was conducted with surgeons in the CCMIJU. The basic shape of the handle that was worked with to determine an ergonomic and customized design for laparoscopic surgery graspers is shown in Figure2. It was the result of the ERGOLAP project [ 38], and is patented (Patent Number EP2471473A1). The ERGOLAP project was carried out by the authors of the present work in coordination with the CCMIJU and with the Institute of Biomechanics of Valencia (IBV).

2.2. Participants The study population comprised 135 surgeons. Their ages ranged from 20 to 70 years (mean age = 39.7 years; SD = 9.78 years), and the distribution of the sample population by sex was 69 female and 66 male. The main anthropometric data of the participants are presented in Table1.

Table 1. Anthropometric data of the study’s participants (n = 135).

Characteristics Mean (SD) Range Age (years) 39.7 (9.78) 20–70 Hand length (mm) 178.9 (13.08) 159.3–194.4 Palm length measured (mm) 96.5 (8.79) 87.6–111.6 Hand breadth digitized (mm) 79.9 (6,98) 71.1–86.5 Appl. Sci. 2018, 8, 1200 4 of 13

Appl. Sci. 2018, 8, x FOR PEER REVIEW 5 of 14 2.3. Experimental Task and the Parametric Prototype Handle 2.3. Experimental Task and the Parametric Prototype Handle The design and development of the handle shown in Figure2 was based on a study of the ergonomicThe design preferences and development of 135 surgeons of the during handle their shown period in of Figure training 2 was in laparoscopic based on a techniques study of the in ergonomicthe CCMIJU. preferences Two of the of handle 135 surgeons design criteriaduring weretheir aperiod large palmarof training grip in surface laparoscopic and the techniques combination in theof precision CCMIJU. and Two turning of the ability.handle Thesedesign criteria criteria eliminated were a large the palmar possibility grip ofsurface a handle and design the combination with rings. of precision and turning ability. These criteria eliminated the possibility of a handle design with rings.

Figure 2. TheThe laparoscopic laparoscopic tool tool handle developed in the ERGOLAP project.

The resultingresulting handle handle design design has has been been studied studied and and further further analyzed analy inzed the in work the work of Gonz ofá Gonzálezlez et al. [18 et]. al.In that[18]. study,In that a study, first approach a first approach was to define was to a grasperdefine a handle grasper size handle that wouldsize that best would suit the best surgeon’s suit the surgeonhand size,’s hand but withoutsize, but attempting without attempting to customize to customi the designze the as design this is as the this purpose is the ofpurpose the paper of the at paperhand, consideringat hand, considering designs baseddesigns on based four handon four sizes hand (XS, sizes S, M, (XS, and S, L). M, The and results L). The of results that work of that are worksummarized are summarized in Table in2. Table It should 2. It should be noted be noted that, inthat, addition in addition to this to this study study of of Gonz Gonzálezález etet al.al. [18], [18], other woworkersrkers have proposed different sizes for surgical handles and hand tools, specificallyspecifically by by definingdefining three sizes [5,16,39 [5,16,39–41].41]. Nonetheless, given the the precision precision required required in surgery and the the many hours that some operations last [36], [36], together with the technologicaltechnological means available today such as additive manufacturing and the development of of 3D parametric design software [42], [42], a personalized solution would seem to be called called for, for, with the handle being designed designed to to have have the the size size ergonomically ergonomically best suited to the anthro anthropometricpometric dimensions of each surgeon surgeon’s’s hand. Recent studies, such as that of Zanetti et et al. al. [43 [43],], show show that thatthe use the of use 3D printing of 3D canprinting bring cansubstantial bring benefits,substantial such benefits, as customization, such as customioptimizationzation and, optimi the manufacturezation and the of manufacture very complex of geometries. very complex geometries.

Table 2.2. Optimal for each of the hand size categories. Hand Size % Sex Mean Diameter (mm) Hand Size % Sex Mean Diameter (mm) XS 26% Both sexes 29.4 XS 26% Both sexes 29.4 11.1% M 32.9 S 11.1% M 32.9 S 18.5% F 31.7 18.5% F 31.7 24.4% M 36.4 M 24.4% M 36.4 M 6.7% F 33.1 6.7% F 33.1 L 13.3% Both sexes 37.9 L 13.3% Both sexes 37.9 The final design of the handle used in this study (Figure 2) allowed us to resolve a series of ergonomicThe final problems design that of the existed handle with used other in thistypes study of MIS (Figure handles2) allowed which usdid to not resolve meet athe series design of criteriaergonomic obtained problems in ERGOLAP. that existed In this with sense, other it typesshould of be MIS noted handles that, since which the did entire not palm meet of the the design hand iscriteria now involved obtained in in gr ERGOLAP.ipping the Inhandle, this sense, it is easier it should to achieve be noted a neutral that, since position theentire of the palm wrist of. T thehis reduceshand is nowfatigue involved and the in risk gripping of thenar the lesions. handle, Hence, it is easier the grip to achieve was designed a neutral inposition such a way of the that wrist. the pressureThis reduces is distributed fatigue and evenly the risk between of thenar the lesions. palm Hence, and the the fingers grip was. Allowing designed g inreater such contact a way that of the handlepressure with is distributed the whole evenly hand avoid betweens flexing the palm the andwrist, the stretching fingers. Allowing tendons, greater distending contact the of elbow, the handle and limitingwith the shoulder whole hand movement. avoids flexing The length the wrist, of the stretching handle and tendons, its diameter distending were increased the elbow, relative and limiting to the handles traditionally used in MIS, as this provides a better fit for different hand sizes, and the fingers have a larger contact surface thus reducing the pressure on localized areas, especially the thumb. Appl. Sci. 2018, 8, 1200 5 of 13 shoulder movement. The length of the handle and its diameter were increased relative to the handles traditionally used in MIS, as this provides a better fit for different hand sizes, and the fingers have a larger contact surface thus reducing the pressure on localized areas, especially the thumb. Regarding the geometry of the handle design developed in the ERGOLAP project (Figure3a), there are three significant parameters. These are identified as the “inferior diameter” (DI), “median diameter” (DM), and “superior diameter” (DS). The median diameter (DM) coincides with the diameter defined at the point of inflection of the curvature of the handle (Figure3a). It also defines the position of the hand relative to the handle during grasping, since for all the surgeons this diameter coincides with the line defined between the third and fourth (Figure3b). Similarly, D S and DI correspond to the narrowest and the broadest parts of the handle design, respectively. These diameters, as shown in Figure3b, in turn coincide with the lines defined between the second and third phalanges in the case of DI and the fourth and fifth phalanges in the case of D . Appl. Sci. 2018, 8, x FOR PEER REVIEW S 6 of 14

(a) (b)

Figure 3. (a) Parameters used in the study; (b) directives for determining the handle position. Figure 3. (a) Parameters used in the study; (b) directives for determining the handle position.

Regarding the geometry of the handle design developed in the ERGOLAP project (Figure 3a), Other features of this handle are that the angle of the handle with the shaft is 45◦ (Figure3b). there are three significant parameters. These are identified as the “inferior diameter” (DI), “median This is a design constraint that must remain unchanged, regardless of the size of the handle or size of diameter” (DM), and “superior diameter” (DS). The median diameter (DM) coincides with the diameter definedthe surgeon’s at the point hand of since inflection it is the of value the curvature recommended of the byhandle previous (Figure studies 3a). It [23 also] and defines was approvedthe position by ofall the the hand surgeons relative who to participated the handle during in the ERGOLAP grasping, since project. for all the surgeons this diameter coincides To define a 3D parametric model of the handle, we chose as the scaling parameter the median with the line defined between the third and fourth (Figure 3b). Similarly, DS and DI correspond to the narrowestdiameter (DandM), the since broadest this is theparts most of the characteristic handle design, diameter respectively. of the design. These It diameters, is defined as theshown line in of Figurethe hand 3b, between in turn coincide the third with and the fourth lines phalanges, defined between and which the must second pass and through third phalanges the point ofin inflexionthe case of the curvature of the handle during grasping. The other parameters that have to be modified to of DI and the fourth and fifth phalanges in the case of DS. properlyOther adapt features the of handle this handle to the surgeon’sare that the hand angle size of arethe DhandleS,DI,R with1, and the R 2shaft(Figure is 45°3b). (Figure The other 3b). Thisparameters is a design are constraint kept invariant, that must affecting remain neither unchanged, the scalability regardless of the of the model size norof the the handle functionality or size of of thethe surgeon design,’ ass hand we explain since it below.is the value We reached recommended this result by byprevious modifying studies in various[23] and wayswas approved the physical by allmodel the surgeons generated who by participated additive manufacturing in the ERGOLAP [42,44 project.], andtesting it on a large number of surgeons. PhysicalTo define models a 3D were parametri manufacturedc model forof the each handle, subject we using chose rapid as the prototyping scaling parameter technology the formedian their subsequent evaluation. All the handles were manufactured with a 3D printer using white ABS plastic diameter (DM), since this is the most characteristic diameter of the design. It is defined as the line of theand hand a smooth between surface the third finish. and fourth phalanges, and which must pass through the point of inflexion of theFor curvature simplicity of ofthe the handle 3D parametric during grasping. CAD handle The model,other parameters we found itthat possible have toto relatebe modified the values to of D ,D ,R , and R , to the value of D . The ratios between D and the other parameters are listed in properlyS I adapt1 the 2handle to the surgeonM ’s hand size are DSM, DI, R1, and R2 (Figure 3b). The other parametersTable3. are kept invariant, affecting neither the scalability of the model nor the functionality of the design, as we explain below. We reached this result by modifying in various ways the physical model generated by additive manufacturing [42,44], and testing it on a large number of surgeons. Physical models were manufactured for each subject using rapid prototyping technology for their subsequent evaluation. All the handles were manufactured with a 3D printer using white ABS plastic and a smooth surface finish. For simplicity of the 3D parametric CAD handle model, we found it possible to relate the values of DS, DI, R1, and R2, to the value of DM. The ratios between DM and the other parameters are listed in Table 3.

Appl. Sci. 2018, 8, 1200 6 of 13

Table 3. Constants which relate the parameters of the handle to DM.

Parameter (mm) Parametric Ratio

DM 1 DI 0.80 DS 1.15 R1 1.25 R2 4.48

2.4. Anthropometric Relationship between the Surgeon’s Hand and the Size of the Handle In this subsection, we shall describe the study that we carried out to relate the anthropometry of the hand to the size of the handle. The aim was to determine which hand measurements are related to the size of the surgical handle developed in this paper to scale the parametric model of the handle to the size most appropriate for each surgeon’s hand. To this end, we started from the base of previous studies of anthropometric dimensions of the hand for the optimal design of everyday utensils. In this sense, one of the most thorough-going works is entitled “Hand Anthropometry of U.S. Army Personnel” [45]. This reports the statistical results of data collected in an anthropometric study of the hands of US Army personnel in 1987 and 1988. The population of that study consisted of 1003 men and 1304 women. The 86 hand dimensions analyzed in the report consisted of 64 measurements obtained photometrically, and 22 direct measurements. Figure4 shows some of these dimensions which have been widely used in anthropometric and ergonomic studies of the hand [5,16,41,46,47]. Greiner’s study is of great importance given the sparsity of the literature that includes any analyses of such a large number of anthropometric parameters of the hand. Such is the case for the design of hand tools whose design can make use of a large number of anthropometric parameters such as the finger length, the width of the hand, and the length of the hand [5,16,41,46–48]. As a complement to this anthropometric study, we also analyzed papers that studied the relationship of the dimensions of the hand with the ergonomic use of hand tools. For example, Matern and Waller [49] presented a detailed analysis of the concave surface of the hand with respect to its longitudinal and lateral dimensions which has a correspondence with the generatrix used in the present work (Figure3b). Using data from the work of Greiner [45], DiMartino et al. [16] defined three categories of hand tools (small, medium, and large) in accordance with hand length. To reduce the number of anthropometric data that we needed to employ in this study, we carried out a comparative study of the different lengths studied by Greiner [45] and those studied by González et al. [18]. In accordance with the aspects indicated above in Section 2.3 that the handle design must meet, the following two criteria were established to determine the most appropriate hand measurements to be analyzed:

• Measurements related to the palm support of the handle—these correspond to the importance of having greater contact between hand and handle, and are therefore related to the breadth of the hand. • Measurements related to the diameter of the handle—these correspond to the handle appropriately fitting the different types of hand, allowing the fingers to have a greater contact surface, and are therefore related to the total length of the hand and the length of the palm. Appl. Sci. 2018, 8, 1200 7 of 13

Appl. Sci. 2018, 8, x FOR PEER REVIEW 8 of 14

FigureFigure 4. (a 4.) Hand(a) Hand Length Length Digitized Digitized (58); (58); ((bb) Hand Length Length Measured Measured (59); (59); (c) Palm (c) Palm Length Length Measured Measured (61); (d) Hand Breadth from Digitizer (62); (e) Hand Breadth Measured (63); (f) Crotch 1 Height (69); (61); (d) Hand Breadth from Digitizer (62); (e) Hand Breadth Measured (63); (f) Crotch 1 Height (69); (g) Crotch 2 Height (70); (h) Crotch 3 Height (71); (i) Crotch 4 Height (72). (g) Crotch 2 Height (70); (h) Crotch 3 Height (71); (i) Crotch 4 Height (72). Based on the above and on the anthropometric measurements of the hand that have already beenBased analy onz theed in above other andworks on on the ergonomics, anthropometric in the present measurements work we analy of thezed hand the following that have three already beenanthropometric analyzed in other parameters works of on the ergonomics, hand: in the present work we analyzed the following three anthropometric• Hand Le parametersngth from Digitizer of the hand:(HLD) (Figure 4a). • Palm Length Measured (PLM) (Figure 4c). • •Hand Hand Length Breadth from from Digitizer Digitizer (HLD) (HBD) (Figure (Figure4 a).4d). • Palm Length Measured (PLM) (Figure4c). To investigate the correspondence between hand size and handle size, we analyzed the • Hand Breadth from Digitizer (HBD) (Figure4d). anthropometric data for the 135 surgeons who participated in this study, as summarized in Table 1. FromTo investigate the values obtained, the correspondence we first calculated between HLD, PLM, hand and size HBD and (Table handle 4, columns size, 3 weto 5) analyzed for each the sex and each hand type as defined in González et al. [18], and then, in order to have parameters that anthropometric data for the 135 surgeons who participated in this study, as summarized in Table1. are very similar in value for any hand size, calculated the ratios between these three sets of From the values obtained, we first calculated HLD, PLM, and HBD (Table4, columns 3 to 5) for each anthropometric values and the optimal median diameter of the handle (Table 4, last three columns). sex and eachThe hand last two type rows as defined of Table in 4 Gonz give á thelez mean et al. [ values18], and and then, standard in order deviations to have parametersof these ratios that are veryweighted similar in according value for to any the handpopulation size, calculated of each sex theand ratios hand betweentype (see theseTable 2). three One sets observes of anthropometric that, of valuesthe and three the anthropometric optimal median ratios, diameter that of of PLM the (a handle measure (Table of the4, lastinner three length columns). of the palm) has the smallestThe last standard two rows deviation of Table 4(0.0 give113021). the mean We therefore values and concluded standard that deviations this ratio ofwould these be ratios the most weighted accordingappropriate to the to population use to relate ofa surgeon each sex’s hand and handsize with type the (see best Table handle2). size One of observesa laparoscopic that, grasper, of the three anthropometricand hence ultimately ratios, that the of best PLM custom (a measure handle ofdesign. the inner length of the palm) has the smallest standard deviation (0.0113021). We therefore concluded that this ratio would be the most appropriate to use to relate a surgeon’s hand size with the best handle size of a laparoscopic grasper, and hence ultimately the best custom handle design. Appl.Appl.Appl.Appl. Appl.Sci. Sci.Appl. Sci. 2018 Sci.Sci.2018 2018Sci. ,2018 20188,, 82018,x ,8 ,xFOR,, 8 x8FOR,, , FOR x8x , FORPEER FORx PEER FOR PEER PEERPEER REVIEW PEERREVIEW REVIEW REVIEWREVIEW REVIEW 9 9of 9of 914of9 14of 9of14 of14 14 14

TableTableTable 4. Relationships 4.4. RelationshipsRelationships between betweenbetween the the theHand HandHand Length LengthLength from fromfrom Digitizer DigitizerDigitizer (HLD ((HLDHLD), Pa)),, lm PaPa lmLengthlm LengthLength Measured MeasuredMeasured (PLM ((PLMPLM), and)),, andand Hand HandHand Breadth BreadthBreadth from fromfrom Digitizer DigitizerDigitizer (HBD ((HBDHBD) dimensions)) dimensionsdimensions and andand Appl.TableTable Sci. 4.Table 2018 Relationships4. Relationships, 4.8, 1200Relationships between between between the the Hand Handthe LengthHand Length Length from from Digitizer from Digitizer Digitizer (HLD (HLD) ,( HLDPa), lmPa) lm,Length Pa Lengthlm Length Measured Measured Measured (PLM (PLM) ,( PLMand), and Hand), andHand BreadthHand Breadth Breadth from from Digitizer from Digitizer Digitizer (HBD (HBD) (dimensionsHBD) dimensions) dimensions and and and8 of 13 thethethe optimalthe theoptimal optimalthe optimaloptimal optimal median median median medianmedian median diameters diameters diameters diametersdiameters diameters of of aof alaparoscopic of of alaparoscopic of alaparoscopica laparoscopiclaparoscopica laparoscopic surgery surgery surgery surgerysurgery surgery handle. handle. handle. handle.handle. handle. Ø ØØ Table 4. Relationships between the Hand Length from Digitizer (HLD), Palm Length MeasuredØ Ø (PLM),Ø and Hand Breadth from Digitizer (HBD) dimensions and the optimal median diametersHandHandHandHand ofHand Hand aLength Length laparoscopic Length LengthLength Length Palm surgeryPalmPalmPalmPalm LengthPalm Length handle.Length LengthLength Length Hand HandHandHandHand HandBreadth Breadth Breadth BreadthBreadth Breadth Optimum Optimum OptimumOptimumOptimumOptimum HSCHSCHSCHSCHSC HSC SexSexSex SexSex Sex fromfromfromfromfrom Digitizerfrom Digitizer Digitizer DigitizerDigitizer Digitizer MeasuredMeasuredMeasuredMeasuredMeasuredMeasured fromfromfromfromfrom Digitizerfrom Digitizer Digitizer DigitizerDigitizer Digitizer Diameter Diameter DiameterDiameterDiameterDiameter AnthropometricAnthropometricAnthropometricAnthropometricAnthropometricAnthropometric Relationship Relationship Relationship RelationshipRelationship Relationship Factor Factor Factor FactorFactor Factor (HLD)(HLD)(HLD)Hand(HLD)(HLD)(HLD) Length (PLM)(PLM)Palm(PLM)(PLM)(PLM)(PLM) Length Hand(HBD)(HBD)(HBD)(HBD)(HBD) Breadth(HBD) ofof ofhandleØ ofhandleof Optimumhandleof handlehandle handle HSC Sex from Digitizer Measured from Digitizer DiameterDDMD MDMD MDM M of Anthropometric Relationship Factor (HLD) (PLM) (HBD) handle DM 푯푳푫푯푳푫푯푳푫푯푳푫푯푳푫푯푳푫 푷푳푴푷푳푴푷푳푴푷푳푴푷푳푴푷푳푴 푯푩푫푯푩푫푯푩푫푯푩푫푯푩푫푯푩푫

UnitsUnitsUnitsUnitsUnits Unitsin in inmm inmmin mm in mm mm mm HLD PLM HBD Units in mm 푫푫푫푴푫푫푴푫푴푴 푫푫푫푴푫푫푴푫푴푴 푫푫푫푴푫푫푴푫푴푴 푴 푴DM D푴M 푴 DM푴 푴

XSXSXS XS XS XS BothBothXSBothBothBoth sexesBoth sexes sexes sexessexes Both sexes sexes 159159159.1593159. 3.159 159.33 . .33 . 3 8787.876. 876 87.687.6 87. .66 . 6 7171. 71.1711. 71171.1 71. .11 . 1 2929.294. 29.4 29429.4 29. .44 . 4 5.54185.418.5 5.4184185 ..4185418 . 418 2. 2.98029802.980.29802 ..9802980 . 980 2.4182.24182.418.24182 ..4182418 . 418 MaleMale 174174.1 .1 97.697 .6 79.179 .1 32.932 .9 5.2925.292 2.9672.967 2.4042.404 MaleMaleMale Male Male 174174.1741 .174 174.11. 1 .1 97.976 97 97.6.697. 6 .6 79. 79.1791 79.179. 1 .1 32.329 32.9 32.932. 9 .9 5.2925.5 5.292292 .2925. 292 2. 2.9679672.2967 .9672. 967 2.4042.4042.2404 .4042. 404 S SS SS S S FemaleFemaleFemaleFemaleFemaleFemale Female 170170170.1702170. 2.170 170.22 . .22 . 2 9494.943. 943 94.394.3 94. .33 . 3 7272. 72.5725. 72572.5 72. .55 . 5 3131.317. 31.7 31731.7 31. .77 . 7 5.53695.369.5 5.3693695 ..3695369 . 369 2. 2.97529752.975.29752 ..9752975 . 975 2.2872.22872.287.22872 ..2872287 . 287 MaleMaleMaleMaleMale Male Male 188188188.1888188. 8.188 188.88 . .88 . 8 107107107.1078 107.8107. 8.1078 . .88 . 8 8686. 86.5865. 86586.5 86. .55 . 5 3636.364. 36.4 36436.4 36. .44 . 4 5.51875.187.5 5.1871875 ..1875187 . 187 2. 2.96229622.962.29622 ..9622962 . 962 2.3762.23762.376.23762 ..3762376 . 376 MM M MM M M FemaleFemaleFemaleFemaleFemaleFemale Female 182182182.1821182. 1.182 182.11 . .11 . 1 9898.982. 982 98.298.2 98. .22 . 2 7878. 78.9789. 78978.9 78. .99 . 9 3333.331. 33.1 33133.1 33. .11 . 1 5.55025.502.5 5.5025025 ..5025502 . 502 2. 2.96729672.967.29672 ..9672967 . 967 2.3842.23842.384.23842 ..3842384 . 384 LL L LL L BothBothBothLBothBoth sexesBoth sexes sexes sexessexes Both sexes sexes 194194194.1949194. 9.194 194.99 . .99 . 9 111111111.1116 111.6111. 6.1116 . .66 . 6 8686. 86.5865. 86586.5 86. .55 . 5 3737.379. 37.9 37937.9 37. .99 . 9 5.51425.142.5 5.1421425 ..1425142 . 142 2. 2.94529452.945.29452 ..9452945 . 945 2.2822.22822.282.22822 ..2822282 . 282 푥 푥푥 푥 푥 x 푥 5.53085.308.55.3083085 ..3085308 . 308 2. 2.96729672.967.29672 ..9672967 . 967 2.3622.23622.362.23622 ..3622362 . 362 푠 푠 푠 s푠푠 푠 0.011730400.1173040.011730400.11730400..117304001173040.1173040 0.0 0.011302101130210.0113021.001130210..011302100113021.0113021 0 0.0549504.005495040.0549504.005495040..054950400549504.0549504

Appl.Appl. Sci. Sci.2018 2018, ,8 8,, 1200 x FOR PEER REVIEW 109 ofof 1314

3.3. ResultsResults andand DiscussionDiscussion TheThe mainmain resultresult ofof thisthis workwork hashas beenbeen toto obtainobtain thethe 3D3D parametricparametric designdesign ofof aa handlehandle forfor thethe graspersgraspers usedused inin laparoscopiclaparoscopic surgery, in which the parameter parameter D DMM allowsallows the the design design to to be be scaled scaled to toadapt adapt the the size size of of the the handle handle to to each each surgeon surgeon’s’s hand hand size. size. In In particular, it was was found found that that the the anthropometricanthropometric measurementmeasurement ofof thethe handhand thatthat isis mostmost appropriateappropriate toto relaterelate thethe handlehandle sizesize toto thethe surgeon’ssurgeon’s handhand sizesize isis thatthat defineddefined byby PLM.PLM. ToTo obtain obtaina a 3D 3D design, design,first firstthe thesurgeon’s surgeon’s PLM PLM value value isis taken.taken. ThisThis valuevalue isis thenthen divideddivided byby thethe coefficientcoefficient 2.9672.967 (see(see TableTable4 )4) to to give give the the most most appropriate appropriate valuevalue ofof thethe medianmedian diameterdiameter ofof thethe handle handle (D(DMM).). WithWith thisthis value,value, thethe 3D3D parametricparametric modelmodel ofof thethe handlehandle is is scaled scaled to to the the surgeon’ssurgeon’s hand hand size. size. FigureFigure5 5shows shows some some examples examples of of 3D 3D CAD CAD models models scaled scaled toto different different surgeons surgeons amongamong thethe participantsparticipants inin thisthis study.study. TheThe curvecurve drawndrawn inin aa dasheddashed lineline onon thethe differentdifferent customized customized models models is is in in this this way way adapted adapted to to the thesurgeon’s surgeon’s hand hand as as shown shown by bythe the equivalentequivalent dasheddashed lineline in in Figure Figure3 b.3b.

FigureFigure 5. 5. CustomCustom 3D 3D ComputerComputer Architectural Architectural Drawings Drawings (CAD) (CAD) modelsmodels of of the the surgical surgical handle handle dependingdepending on on each each surgeon’s surgeon’s PLM PLM measurement. measurement.

ToTo check check the the results, results, several several 3D 3D CAD CAD parametric parametric designs designs for for different different surgeons surgeons were were fabricated fabricated by additiveby additive manufacturing manufacturing (for different(for different sexes sexes and hand and hand sizes). sizes). Figure Figure6 shows 6 shows one of theseone of handles these handles made formade a particular for a particular value of value PLM, andof PLM, therefore and withtherefore a characteristic with a characteristic value of DM value(a value of D thatM (a determines value that thedetermines complete the design complete of the design handle). of the For handle). this, first For the this, surgeon’s first the hand surgeon was’s scanned, hand was to scanned, then obtain to then the palmobtain length the palm (PLM), length in this (PLM), case giving in this a valuecase giving of 96.55 a mm.value The of 96.55 optimal mm. diameter The optimal was calculated diameter from was thecalculated anthropometric from the ratio anthropometric PLM/DM resulting ratio P inLM/D a customM resulting value ofin Da Mcustom= 32.54 value mm, whichof DM was= 32.54 used mm, to generatewhich was the used parametric to generate model the of parametric the handle model (Figure of6). the handle (Figure 6). ToTo be be fully fully functional functional for for the the validation validation tests,tests, thethe 3D3D CADCAD modelmodel waswas designeddesigned withwith aa hollowhollow interior.interior. This This allowed allowed the the shaft shaft (the (the metallic metallic clip) clip) to to be be insertedinserted togethertogether with with thethe openingopening andand closingclosing mechanismsmechanisms of of the the grasper grasper and and the the shaft’s shaft’s rotation rotation mechanism mechanism (Figure (Figure6 ).6). Appl. Sci. 2018, 8, 1200 10 of 13 Appl. Sci. 2018, 8, x FOR PEER REVIEW 11 of 14 Appl. Sci. 2018, 8, x FOR PEER REVIEW 11 of 14

(a) (b) (a) (b) Figure 6. Prototype custom handle. (a) Details of the pieces; (b) assembled prototype. Figure 6. Prototype custom handle. ( a)) Details Details of the the pieces; ( b) a assembledssembled prototype.

Figure 7 shows a surgeon using the prototype (DM = 32.54 mm) during the validation test. At the Figure7 7 shows shows aa surgeonsurgeon using using the the prototype prototype (D (DM = 32.54 32.54 mm) during the validation test. At the conclusion of the test, the surgeon confirmed that theirM experience using the handle was completely conclusion of the test, the surgeon confirmed confirmed that their experience using the handle was completely satisfactory [18]. Identical results were obtained with the surgeons whose handles corresponded to satisfactory [18]. [18]. Identical results results were obtained with the surgeons whose handles corresponded to those illustrated in Figure 5. those illustrated in Figure5 5..

Figure 7. Prototype custom handle used in a simulation test. Figure 7. Prototype custom handle used in a simulation test. 4. Conclusions 4. Conclusions The main finding of this work was confirmation that it is possible to obtain 3D parametric The main finding of this work was confirmation that it is possible to obtain 3D parametric designsThe of main a handle finding for of this laparos workcopic was confirmation graspers that that are it scalable is possible to to fit obtain each 3D surgeon parametric’s hand designs size. designs of a handle for laparoscopic graspers that are scalable to fit each surgeon’s hand size. ofFurthermore, a handle for it laparoscopicwas found that graspers a single that anthropometric are scalable to factor fit each—the surgeon’s “Palm Length hand size. Measured Furthermore,”—can Furthermore, it was found that a single anthropometric factor—the “Palm Length Measured”—can itbe was used found to relate that aany single surgeon anthropometric’s hand size factor—the to the optimal “Palm diameter Length Measured”—can of the handle. beFunctional used to relatetests be used to relate any surgeon’s hand size to the optimal diameter of the handle. Functional tests anycarried surgeon’s out in the hand CCMIJU size to confirmed the optimal that diameter the parametric of the handle. design Functionaldeveloped testsfor the carried handles out adapts in the carried out in the CCMIJU confirmed that the parametric design developed for the handles adapts CCMIJUergonomically confirmed to different that the surgeon parametric’s hand design sizes. developed for the handles adapts ergonomically to ergonomically to different surgeon’s hand sizes. differentThus, surgeon’s the specific hand contributions sizes. of this work include the following: Thus, the specific specific contributions of this work include the following: • A 3D parametric CAD design has been obtained for the handle of laparoscopic surgery graspers • A 3D parametric CAD design has been obtained for the handle of laparoscopic surgery graspers • Athat 3D is parametric scalable for CAD different design hand has beensizes. obtained All of the for resulting the handle models of laparoscopic personally surgery customized graspers for that is scalable for different hand sizes. All of the resulting models personally customized for thateach issurgeon scalable complied for different with handthe ergonomic sizes. All criteria of the resultingfor their use. models personally customized for each surgeon complied with the ergonomic criteria for their use. • eachThe resultssurgeon show complied that with additive the ergonomicmanufacturing criteria and for thetheir application use. of ergonomics criterion • The results show that additive manufacturing and the application of ergonomics criterion provide an efficient method for the customized design and manufacture of this type of provide an efficient method for the customized design and manufacture of this type of specialized tools, being possible to be applicable to other sectors. specialized tools, being possible to be applicable to other sectors. Appl. Sci. 2018, 8, 1200 11 of 13

• The results show that additive manufacturing and the application of ergonomics criterion provide an efficient method for the customized design and manufacture of this type of specialized tools, being possible to be applicable to other sectors. • The relationship between the anthropometry of the surgeon’s hand and the most suitable size of the handle was determined, with the most suitable anthropometric parameter to measure being the “Palm Length Measured” (PLM).

Finally, the authors consider that the customization of the geometry of a surgical tool can serve as a reference for future research that addresses the optimal material and tools for their subsequent production through additive manufacturing techniques.

Author Contributions: Conceptualization, A.G.G. and D.R.S.; Formal analysis, D.R.S. and A.S.R.; Investigation, A.G.G., D.R.S. and L.G.M.; Methodology, A.G.G.; Software, L.G.M.; Validation, A.G.G., D.R.S., L.G.M. and A.S.R.; Writing–review & editing, A.G.G. and D.R.S. Funding: This research received no external funding. Acknowledgments: The authors wish to acknowledge the support of this research work to the VI Regional Research Plan and the Regional Government of Extremadura and to the Fondo Social Europeo (FEDER) linked to the financial of the research groups Manufacturing Engineering (GR-18029) and INNOVA RNM020—Design, Sustainability and Added Value (GR-18015). The authors are grateful for the outstanding willingness to cooperate of the 135 surgeons who participated in the study, and for their interest in following through with the appropriate trials so as to obtain a satisfactory outcome. In particular, they all considered it of great importance to adapt the sizes of the handles of the tools they use to the size of their hands. Conflicts of Interest: The authors declare no conflicts of interest.

References

1. Mace, R.L. Universal Design Universal Design: Barrier free environments for everyone. Design. West 1985, 33, 147–152. 2. Mace, R.L.; Ostroff, E.; Connell, B.R.; Jones, M.; Mueller, J.; Mullick, A.; Sanford, J.; Steinfeld, E.; Follette Story, M.; Vanderheiden, G. The Principles of Universal Design; Center for Universal Design, NC State University: Raleigh, ND, USA, 1997. 3. Story, M.F.; Mueller, J.L.; Mace, R.L. The Universal Design File: Designing for People of All Ages and Abilities; Center for Universal Design, NC State University: Raleigh, ND, USA, 1998. 4. Clarkson, P.J.; Coleman, R. History of in the UK. Appl. Ergon. 2015, 46, 235–247. [CrossRef] [PubMed] 5. Berguer, R.; Hreljac, A. The relationship between hand size and difficulty using surgical instruments: A survey of 726 laparoscopic surgeons. Surg. Endosc. 2004, 18, 508–512. [CrossRef][PubMed] 6. Alleblas, C.C.J.; Vleugels, M.P.H.; Nieboer, T.E. Ergonomics of laparoscopic graspers and the importance of haptic feedback: the surgeons’ perspective. Gynecol. Surg. 2016, 13, 379–384. [CrossRef][PubMed] 7. Stoklasek, P.; Mizera, A.; Maˇnas,M.; Maˇnas, D. Improvement of handle grip using reverse engineering, CAE and Rapid Prototyping. In Proceedings of the 20th International Conference on Circuits, Systems, Communications and Computers (CSCC 2016), Corfu Island, Greece, 14–17 July 2016. 8. Sutton, E.; Irvin, M.; Zeigler, C.; Lee, G.; Park, A. The ergonomics of women in surgery. Surg. Endosc. 2013, 28, 1051–1055. [CrossRef][PubMed] 9. Groenesteijn, L.; Eikhout, S.M.; Vink, P. One set of pliers for more tasks in installation work: The effects on (dis)comfort and productivity. Appl. Ergon. 2004, 35, 485–492. [CrossRef][PubMed] 10. Kong, Y.-K.; Lowe, B.D.; Lee, S.J.; Krieg, E.F. Evaluation of handle design characteristics in a maximum screwdriving torque task. Ergonomics 2007, 50, 1404–1418. [CrossRef][PubMed] 11. Harih, G.; Dolšak, B. Tool-handle design based on a digital human hand model. Int. J. Ind. Ergon. 2013, 43, 288–295. [CrossRef] 12. Harih, G.; Dolšak, B. Comparison of subjective comfort ratings between anatomically shaped and cylindrical handles. Appl. Ergon. 2014, 45, 943–954. [CrossRef][PubMed] 13. Sancho-Bru, J.L.; Giurintano, D.J.; Pérez-González, A.; Vergara, M. Optimum tool handle diameter for a cylinder grip. J. Hand Ther. 2003, 16, 337–342. [CrossRef] Appl. Sci. 2018, 8, 1200 12 of 13

14. Kong, Y.K.; Kim, D.M.; Lee, K.-S.; Jung, M.-C. Comparison of comfort, discomfort, and continuum ratings of force levels and hand regions during gripping exertions. Appl. Ergon. 2012, 43, 283–289. [CrossRef] [PubMed] 15. Berguer, R.; Forkey, D.L.; Smith, W.D. Ergonomic problems associated with laparoscopic surgery. Surg. Endosc. 1999, 13, 466–468. [CrossRef][PubMed] 16. DiMartino, A.; Doné, K.; Judkins, T.; Morse, J.; Melander, J. Ergonomic Laparoscopic Tool Handle Design. In Proceedings of the Human Factors and Ergonomics Society Annual Meeting, New Orleans, LA, USA, 20–24 September 2004; SAGE Publications: Los Angeles, CA, USA, 2004; pp. 1354–1358. 17. Trejo, A.; Jung, M.C.; Oleynikov, D.; Hallbeck, M.S. Effect of handle design and target location on insertion and aim with a laparoscopic surgical tool. Appl. Ergon. 2007, 38, 745–753. [CrossRef][PubMed] 18. González, A.G.; Salgado, D.R.; García Moruno, L. Optimisation of a laparoscopic tool handle dimension based on ergonomic analysis. Int. J. Ind. Ergon. 2015, 48, 16–24. [CrossRef] 19. Openshaw, S.; Taylor, E. Ergonomics and Design. Reference Guide; All Steel Inc.: Muscatine, IA, USA, 2006. 20. Worksafe, Travail Sécuritaire. Office Ergonomics. Guidelines for Preventing Musculoskeletal Injuries; WorkSafeNB: Saint John, NB, Canada, 2010. 21. Scott, P.; Kogi, K.; McPhee, B. Ergonomics Guidelines for Occupational Health Practice in Industrially Developing Countries; International Ergonomics Association: Darmtstadt, Germany, 2009. 22. Chapanis, A. Ergonomics in product development: a personal view. Ergonomics 1995, 38, 1625–1638. [CrossRef] 23. Van Veelen, M.A.; Meijer, D.W.; Uijttewaal, I.; Goossens, R.H.; Snijders, C.J.; Kazemier, G. Improvement of the laparoscopic needle holder based on new ergonomic guidelines. Surg. Endosc. 2003, 17, 699–703. [CrossRef] [PubMed] 24. Wauben, L.S.; Van Veelen, M.A.; Gossot, D.; Goossens, R.H. Application of ergonomic guidelines during minimally invasive surgery: A questionnaire survey of 284 surgeons. Surg. Endosc. 2006, 20, 1268–1274. [CrossRef][PubMed] 25. Parekh, J.; Shepherd, D.; Hukins, D.; Maffulli, N. Ergonomic T-Handle for Minimally Invasive Surgical Instruments. Transl. Med. UniSa 2016, 14, 38–41. [PubMed] 26. Berguer, R. The application of ergonomics in the work environment of general surgeons. Rev. Environ. Health 1997, 12, 99–106. [CrossRef][PubMed] 27. Berguer, R. Surgery and ergonomics. Arch. Surg. 1999, 134, 1011–1016. [CrossRef][PubMed] 28. Matern, U.; Eichenlaub, M.; Waller, P.; Ruckauer, K. MIS instruments. An experimental comparison of various ergonomic handles and their design. Surg. Endosc. 1999, 13, 756–762. [CrossRef][PubMed] 29. Van Veelen, M.A.; Meijer, D.W. Ergonomics and design of laparoscopic instruments: results of a survey among laparoscopic surgeons. J. Laparoendosc. Adv. Surg. Tech. Part B Videoscop. 1999, 9, 481–489. [CrossRef] [PubMed] 30. Szeto, G.P.; Cheng, S.W.; Poon, J.T.; Ting, A.C.; Tsang, R.C.; Ho, P. Surgeons’ Static Posture and Movement Repetitions in Open and Laparoscopic Surgery. J. Surg. Res. 2011, 172, 19–31. [CrossRef][PubMed] 31. Choi, S. A Review of the Ergonomic Issues in the Laparoscopic Operating Room. J. Healthc. Eng. 2012, 3, 587–603. [CrossRef] 32. Berguer, R.; Chen, J.; Smith, W.D. A comparison of the physical effort required for laparoscopic and open surgical techniques. Arch. Surg. 2003, 138, 967–970. [CrossRef][PubMed] 33. Smith, W.D.; Forkey, D.L.; Berguer, R. The Virtual Instrumentation (VI) laboratory facilitates customized on- site ergonomic analysis of minimally invasive surgery. Stud. Health Technol. Inform. 1998, 50, 240–245. [CrossRef][PubMed] 34. Hemal, A.K.; Srinivas, M.; Charles, A.R. Ergonomic problems associated with laparoscopy. J. Endourol. 2001, 15, 499–503. [CrossRef][PubMed] 35. Quick, N.E.; Gillette, J.C.; Shapiro, R.; Adrales, G.L.; Gerlach, D.; Park, A.E. The effect of using laparoscopic instruments on muscle activation patterns during minimally invasive surgical training procedures. Surg. Endosc. 2003, 17, 462–465. [CrossRef] [PubMed] 36. Trejo, A.; Doné, K.N.; DiMartino, A.; Oleynikov, D.; Hallbeck, M.S. Articulating vs. conventional laparoscopic grasping tools-surgeons’ opinions. Int. J. Ind. Ergon. 2006, 36, 25–35. [CrossRef] 37. Park, A.; Lee, G.; Seagull, F.J.; Meenaghan, N.; Dexter, D. Patients benefit while surgeons suffer: An impending epidemic. J. Am. Coll. Surg. 2010, 210, 306–313. [CrossRef][PubMed] Appl. Sci. 2018, 8, 1200 13 of 13

38. Ergolap Project. Obtaining Criteria for Ergonomic Design of Laparoscopic Surgery Instruments; National Project of the Spanish Gov.; Ref.: DPI2007-65902-C03-03; Ministry of Science and Innovation: Madrid, Spain, 2008–2010. 39. Kong, Y.-K.; Lowe, B.D. Optimal cylindrical handle diameter for grip force tasks. Int. J. Ind. Ergon. 2005, 35, 495–507. [CrossRef] 40. Kong, Y.-K.; Lowe, B.D. Evaluation of handle diameters and orientations in a maximum torque task. Int. J. Ind. Ergon. 2005, 35, 1073–1084. [CrossRef] 41. Sekulova, K.; Buresa, M.; Kurkinb, O.; Simona, M. Ergonomic Analysis of a Firearm According to the Anthropometric Dimension. Procedia Eng. 2015, 100, 609–616. [CrossRef] 42. Hsiao, S.W.; Chuang, J.C. A reverse engineering based approach for product form design. Des. Stud. 2003, 24, 155–171. [CrossRef] 43. Zanetti, E.M.; Aldieri, A.; Terzini, M.; Calì, M.; Franceschini, G.; Bignardi, C. Additively manufactured custom loadbearing implantable devices: grounds for caution. Australas. Med. J. 2017, 10, 694. [CrossRef] 44. Sass, L.; Oxman, R. Materializing design: the implications of rapid prototyping in digital design. Des. Stud. 2005, 27, 325–355. [CrossRef] 45. Greiner, T.M. Hand Anthropometry of U.S. Army Personnel; Technical Report NATICK/TR-92/011; United States Army Natick Research, Development and Engineering Center: Natick, MA, USA, 1991. 46. Irwin, C.B.; Radwin, R.G. A new method for estimating hand internal loads from external force measurements. Ergonomics 2008, 51, 156–167. [CrossRef][PubMed] 47. Lee, K.-S.; Jung, M.-C. Ergonomic Evaluation of Biomechanical Hand Function. Saf. Health Work 2015, 6, 9–17. [CrossRef][PubMed] 48. Oh, S.; Radwin, R. Pistol Grip Power Tool Handle and Trigger Size Effects on Grip Exertions and Operator Preference. Hum. Factors 1993, 35, 551–569. [CrossRef][PubMed] 49. Matern, U.; Waller, P. Instruments for minimally invasive surgery: principles of ergonomic handles. Surg. Endosc. 1999, 13, 174–182. [CrossRef] [PubMed]

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).