Development of prototyping as an alternative for trauma reconstruction in a common sloth limb (Bradypus variegatus) Desenvolvimento de prototipagem como alternativa de reconstrução de trauma em membro de preguiça-comum (Bradypus variegatus)

Specimens of Bradypus variegatus are commonly found with thoracic limbs lesions, victims of electric shock sit-ins or trampling, presenting injuries such as loss of claws and fractures, compromising their locomotion and ability to pick up their food causing the animal to die. The aim of this study was to perform a prototyping of the common sloth limb (Bradypus variegatus), using radiographic images, digital modeling software and 3D printing, for future implantation in common sloths who suffered trauma in thoracic limb. Thus, it was intended to compensate for the absence of bone structure by rapid prototyping, establishing at least the possibility of support and to obtain food.


INTRODUÇÃO
The number of wild animals moving to urban or urbanized areas is increasing and this occurs because of anthropic actions (CURITIBA, 2012), where, due to these factors, several biological models, including sloths, are threatened (AZARIAS et al., 2006).
Because it is a species with arboreal habits, sloths are susceptible to electric shocks and, therefore, are frequent victims for veterinary intervention (PETRUCCI et al., 2009;ARAÚJO et al., 2010). As pointed out by Correia Júnior and Corrêa (2013), the same is used for individuals who inhabit forest fragments cut by highways or roads, which end up being victims of trampling, after attempting to cross the roads towards the other part of the fragment, and in both situations specimens have as a result serious injuries such as loss of claws and fracture of limbs, or even death.
According to Petrucci et al. (2009), Araújo et al. (2010), the most common causes of veterinary interventions in these animals, when found in urban areas, are electric shocks, when, through trees, they reach high voltage poles, located on the edge of forest, becoming victims of electrical discharges, when moving through the treetops.
With technological advances, it was possible to apply some innovations, so that in the areas of health, 3D printing or rapid prototyping has been used in human medicine, veterinary medicine and dentistry, with production of biomodels (SEARS et al., 2016) and, for this, 3D printers have emerged as a favorable option for construction of complete anatomical parts, in order to establish and validate the best positioning and treatment (SHIN-WOOK et al., 2014).
Three-dimensional models of bone regions are not easy to obtain, mainly due to their geometry complexity. Thus, the construction of images can be done from two distinct forms: with the use of computed tomography, using software that unites twodimensional figures formed by this methodology and transform them into 3D images (JÓIA FILHO, 2008), or with a 3D scanner, and this method is widely used for presenting good spatial resolution and being economically accessible (SCAGLIUSI, 2015).  The present study aimed to perform a prototyping of common sloth limb (Bradypus variegatus), using radiographic images, digital modeling software and 3D printing, for future implantation in specimens that suffered trauma to thoracic limb.

MATERIAL AND METHOD
Two specimens of B. variegatus were used, one from São Judas Tadeu  From the acquisition of radiographic images, the procedure was divided into stages, the process of elaboration of prosthesis model of claws of this species was initiated, with support of the Maker Space laboratory of the São Judas Tadeu University Center -Unimonte Campus, using digital modeling software.
Inkscape® (an image editing software) was used to create the claw of the animal.
With the same program, vectorization of this structure was performed in 2D from the radiographic image. After obtaining the image of the contour of claws in 2D, it was transferred to Blender® program, in which transformation to 3D and triplicate of the structure occurred, creating the three-claw digital model. With the use of geometric shape from a cube, a glove was formulated, in which claws were inserted, forming the model of the prosthesis in three-dimensional format.
With digitally generated 3D model, a 3D printing of the physical model of the prosthesis was performed, using Cliever CL2 Pro Plus® printer, which has as its manufacturing principle a technique named Fused Deposition Modeling -FDM, characterized by the overlap of castings, for this research, thermoplastic polylactic acid (PLA) with a height of 0.2 mm. After this process, the prosthesis received a finish of its shape and the orifices were filled with 3D Pen equipment®.
It is worth to highlight the intentionality of the use of free softwares, since these are technological tools that provide an opportunity to democratize access to digital modeling in several areas of knowledge.

RESULTS AND DISCUSSION
Rapid prototyping is on the rise in the health area, where it has been used in human medicine, veterinary medicine, and dentistry, with production of biomodels (Sears et al.

2016).
According to Grando (2005), rapid prototyping is a technology that allows the direct relationship between real anatomy and the model to be generated, and for this reason this work proposed to develop a prototyping of the claws of the species Bradypus variegatus, since these animals are often found ran over and electrocuted, and the most affected area is usually the thoracic members and claws, a fundamental structure for the survival of a species that lives in trees.
On radiography of the extremity of thoracic limb, carpal bones, metacarpic bones, proximal, middle and distal phalanges and claws of a healthy animal ( Fig. 1A and B) and of an animal that was electrocuted with claw injury are observed. It is noted that the species has five metacarpals, metacarpals II, III and IV developed and metacarpals I and V rudimentary (Fig. 1), a data compatible with that found by Freitas et al. (2017) in pelvic limb research for that species.
From the radiographic images of the claws of B. variegatus, an image editing software (Inkscape®) was used to perform the vectorization of this structure in 2D ( Fig.   2A). After obtaining the image of the contour of the claws in 2D, it was transferred to Blender® program, in which the transformation to 3D and triplicate of the structure occurred, creating the image of three claws. With the use of the geometric shape from a cube, a glove was formulated, in which the claws were inserted, forming the model of prosthesis in three-dimensional format (Fig. 2B).  With the digitally generated 3D model, a physical model of the prosthesis was performed using the Cliever CL2 Pro Plus ® (Fig. 3A) printer, which has as its manufacturing principle the Technique Fused Deposition Modeling -FDM, characterized by the overlap of fused layers -in the case of this research, of polylactic acid (PLA) -with a height of approximately 0.2 mm. After this process, the prosthesis received a finish of its shape and fill of orifices with the 3D Pen®. It is worth considering that there are, in the market, a variety of materials to be used as filament, with characteristics such as strength and quality of finish that vary according to the use and function for which they are intended. Among others, there is Acrinolitrin Estyrene Butadiene (ABS), Polyethylene Terephthalate with Glycol (PETG) and Lactic Polyacid (PLA), which was applied in the research for the manufacture of the biomodel. It should also be emphasized that, in preliminary tests, in relation to resistance in compression tests, ABS proved to be the preferred option. On the other hand, PLA presented lower deformation and better performance in three-point bending tests (MARTINEZ et al.,2017), and is therefore the most indicated material for the model to which it would be intended.
The biomodel has three claws and an area to fit the animal's limb, as well as cracks for velcro placement to attach it to the specimen (Fig. 3B).
In a research conducted by Reis et al. (2017) and Veneziani (2017) anatomical structures were scanned in a 3D scanner for subsequent 3D printing by an appropriate printer, and no imaging tests were used, unlike the present study, in which radiography was used to obtain two-and three-dimensional images, using software, with subsequent support formation processes, slicing for print preparation , followed by 3D printing of the final model and finishes, corroborating such procedures with Antas (2007).
Printing of the claws of B. variegatus, with a 3D printer Cliever CL2 ProPlus®, the prosthesis model was obtained for these structures, which was thermoplastic, where the use of cited material was in accordance with that used by Reis et al. (2017) in their research.

CONCLUSION
As pointed out in the present study, Bradypus variegatus is often the victim of trampling and electric shocks, a fact that often compromises its extremities, causing the specimen to require veterinary medical interventions, for which knowledge is important regarding the anatomy of the species.
According to radiographic images analyzed in the present study, it was possible to observe that in this species the humerus bone is considerably long and that the radio and ulna bones are not fused, unlike some species and compatible with that presented in the anteater (Myrmecophaga tridactyla), agoutis (Dasyprocta spp) and in man. In addition, it is possible to visualize fissary discs, demonstrating the animal as young. Five metacarpals were found in the images of the extremities of thoracic limbs, with rudimentary I and V and II, III and IV developed.
With the use of radiographic images, it was possible to obtain the bi-and threedimensional images, thus continuing the process of rapid prototyping of the biomodel of the prosthesis of B. variegatus claws. The final product was developed in thermoplastic material, in which, at one end, the space for fitting the animal member is present, while at the other end are the replicas of the claws.
Thus, the present work allowed greater anatomical knowledge of this species, as well as provided an initial anatomical biomodel, and may in future help in the actions of conservation of the species and individuals welfare.