## 1 Introduction  
Universal object designs try to fit all users using the criterion known as \"design for all\" [1]. This criterion is included in the \"Universal Design\" 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 [PERSON] et al. [2] was further developed by [PERSON] 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, [PERSON] 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 [PERSON] et al. [7] on tools used for the assembly of electric motors, show that while 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 of the tool were not. Prolonged use of tools with poor ergonomic design was shown to cause discomfort resulting in numbness or paraesthesia (\"pins and needles\") in the workers' fingers. Hand size is a determining factor in how precision tools, in particular laparoscopic graspers, are used [8]. Small-handed surgeons experience more grip problems than those with large hands, and are forced to hold the handle differently from what was originally considered in its design phase [8]. Current surgical laparoscopic tools usually come in a standard size, and the surgeon must adapt accordingly by holding and gripping them in certain ways, which a priori depend on the size of his or her hand. The conventional laparoscopic surgery graspers shown in Figure 1 incorporate a pistol grip mechanism with finger rings, and a mechanism that allows full rotation of the tip of the shaft (upper part of the graspers). The three images in the figure show different forms of gripping the instrument depending on the size of the user's hand. In the case of Figure 1a, a surgeon with a small hand holds the handle without being able to encompass all of the instrument's grasping elements. In Figure 1b, the opposite case is revealed: A surgeon with a large hand is unable to make simultaneous use of most of those elements, and grips the handle in a completely different way. The ideal grip would be that shown in Figure 1c, in which all the grasping elements fit the size of the hand perfectly. It is important to note that the grips represented in Figure 1 are not arbitrary, but rather reflect real situations brought about when the size of the hand and the dimensions of the handle do not correspond. These different grips were observed in the Centro de Cirugia de Minima Invasion Jesus Uson (CCMIJU) which collaborated in the development of the present study. At present, as various recent studies have observed [9; 10; 11; 12], the instruments used in laparoscopic surgery are characterized by being of a single size (as mentioned above) and with little ergonomy in their design.