Design for personalized medicine in orthotics and prosthetics

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Design personalized medicine in orthotics and prosthetics Design for for28th personalized medicineMay in 2018, orthotics prosthetics CIRP Design Conference, Nantes, and France Marco Leitea, Bruno Soaresa, Vanessa Lopesb, Sara Santosb, Miguel T. Silvab

b Marco Leitea, Bruno Soaresa, Vanessa Lopesb, Saraand Santos , Miguelarchitecture T. Silvab A new methodology to analyze the functional physical of UNIDEMI, Departamento de Engenharia Mecânica e Industrial, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Caparica, Portugal UNIDEMI, Departamento de Engenharia Mecânica e Industrial, de Ciências de e Tecnologia, Universidade NOVA de Lisboa, Caparica, Portugal IDMEC, Instituto Superior Faculdade Técnico, Universidade Lisboa, Lisboa, Portugal existing products for an assembly oriented product family identification IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal a a

b b

* Corresponding author. E-mail address: [email protected] * Corresponding author. E-mail address: [email protected]

Paul Stief *, Jean-Yves Dantan, Alain Etienne, Ali Siadat

Abstract Abstract

École Nationale Supérieure d’Arts et Métiers, Arts et Métiers ParisTech, LCFC EA 4495, 4 Rue Augustin Fresnel, Metz 57078, France

* Corresponding author. Tel.: +33 3 87 37 54 30; E-mail address: [email protected]

Personalized medicine is a trend where the approach to the treatment is focused on the patient, rather than an approach where “one size fits all”. Personalized is a trend where the approach to the focused the patient, rather than where “oneaddress size fitsthose all”. The objectivemedicine is to develop devices and treatments where thetreatment needs of is doctors andonpatients are attended, andan theapproach generated concepts The objective is to develop devices and treatments where the needs of doctors and patients are attended, and the generated concepts address those needs. needs. Abstract Additive manufacturing is an enabler of these types of devices, since it is a technology well adapted to complex shapes and one series production. Additive manufacturing is an enabler of these types of devices, since it is a technology well adapted to complex shapes and one series production. In today’s business environment, the trend towards more product variety and customization is unbroken. Due to this development, the need of In this paper, the authorsproduction present twosystems case studies in rehabilitation, one for a knee positioning orthosis for an adolescent with cerebralproduction palsy and agile and reconfigurable emerged to cope with one various and product families. design and optimize In paper, authors arm present case studies rehabilitation, for aproducts knee positioning orthosis for anToadolescent with cerebral and thethis other for athe prosthetic for atwo toddler. In bothin cases the product adoptedanalysis methodology is similar: from imageology images, aknown generation ofpalsy concepts systems as well as to choose the optimal product matches, methods are needed. Indeed, most of the methods aim to the other for a prosthetic arm for a toddler. In both cases the adopted methodology is similar: from imageology images, a generation of concepts is embodied and manufactured thethe usephysical of 3D printers. The use of adequate materials allowsmay for the generation orthosis andnumber prosthetics analyze a product or one productthrough family on level. Different product families, however, differ largely inof of the and is embodied and manufactured through the use of 3D printers. The userecommendations. of adequate materials allows for the generation ofterms orthosis and prosthetics fully customized to the patients’ needs and aligned with the doctor’s nature of components. This fact impedes an efficient comparison and choice of appropriate product family combinations for the production fully customized to the patients’ needs and aligned with the doctor’s recommendations. system. A new methodology is proposed to analyze existing products in view of their functional and physical architecture. The aim is to cluster Personalized will allow for a product reduction of rejection an increase of patient’s quality lifethe and to a reduction a delaying of these products medicine in new assembly oriented families for thelevels, optimization of existing assembly linesof of futureor Personalized medicine will two allow forstudies a reduction of rejection levels, an the increase of patient’s quality ofand life andcreation to a reduction orreconfigurable a delaying of downstream problems. The case presented here demonstrate potential for additive manufacturing in the area of rehabilitation. assembly systems. BasedThe on two Datum Chain, the physical structure ofthe thepotential productsfor is analyzed. Functional subassemblies identified, and downstream problems. caseFlow studies presented here demonstrate additive manufacturing in the area ofare rehabilitation. a functional analysis is performed. Moreover, a hybrid functional and physical architecture graph (HyFPAG) is the output which depicts the © Authors. Published by B.V. similarity between product families by providing © 2019 2019 The The Authors. Published by Elsevier Elsevier B.V. design support to both, production system planners and product designers. An illustrative © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of Design Conference 2019 Peer-review under responsibility of the scientific committee of the the CIRP CIRPAn Design Conference 2019. example of a nail-clipper is used to explain the proposed methodology. industrial case study on two product families of steering columns of Peer-review under responsibility of the scientific committee of the CIRP Design Conference 2019 thyssenkrupp Presta France is then carried out to give a first industrial evaluation of the proposed approach. Keywords: Rehabilitation; Product Design; Concept generation; Additive Manufacturing. ©Keywords: 2017 TheRehabilitation; Authors. Published Elsevier B.V.generation; Additive Manufacturing. Product by Design; Concept Peer-review under responsibility of the scientific committee of the 28th CIRP Design Conference 2018. Keywords: Assembly; Design method; Family identification

1. Introduction 1. Introduction

field, the orthopaedics service is specialized in the manufacture field,adjustment the orthopaedics service is specialized in the manufacture and of prosthesis/orthosis (P/O), which includes and adjustment of prosthesis/orthosis (P/O), which includes determining patient needs, assessing anatomy, musculoskeletal Personalized Medicine is a growing approach to determining patient needs, assessing anatomy, musculoskeletal Personalized Medicine is a growing approach to structure and extent injury in order to determine the best type care. Although the term has risen to prominence due to 1.patient Introduction of the product rangeof characteristics manufactured and/or structure and extent ofand injury in order tomonitoring determine the best type patient care. Although the term has risenfor toaprominence due to of P/O, as well as continuously the patient advances in genome mapping that allow targeted approach assembled in this system. In this context, the main challenge in of P/O, as well as continuously monitoring the patient advances in genome mapping that allow for a targeted approach condition and adaptation tonow the device. to Due medicine, its usefast has nowadays a much broader application to the development in the domain of modelling and analysis is not only to cope with single condition and adaptation to the device. to its use has nowadays much medicine broader application the discipline moved away from [1].medicine, Personalized medicine can alsoatrend mean that takes communication and an ongoing ofmedicine digitization and products, Although a limited product range or has existing product families, Although the discipline has moved away from [1]. Personalized medicine can also mean that takes prefabricated P/O, which in some cases hampered the success into account such needs as patient response and preference, digitalization, manufacturing enterprises are facing important but also to be able towhich analyze and tocases compare products tosuccess define prefabricated P/O, in some hampered the into account such needs as patient response and preference, rate of therapy and/or patient acceptance of the device, into response to in treatment, opposition to the traditional “one size challenges today’s in environments: a continuing new families. It can be observed that classical existing rate product ofpersonalized therapy and/or acceptance device, into response to treatment, inmarket opposition to the traditional “one size more P/O,patient the standard methodofofthe manufacturing fits all approach” [2], [3]. tendency towards reduction of product development times and product families areP/O, regrouped in function of clients or features. more personalized the standard method of manufacturing fits all approach” [2], [3]. is still a time consuming, arduous and wasteful process, not This is true in rehabilitation medicine, especially shortened This product In addition, there is an increasing However, assembly orientedarduous product and families are hardly to find. is still a time consuming, wasteful process, not is lifecycles. true in which rehabilitation medicine, completely personalized. physical rehabilitation, is already on theespecially path of completely personalized. demand ofrehabilitation, customization,which being at the same on timethe in apath global On the product family level, products differ mainly in two physical is already of personalized medicine since, in most cases, to each patient is competition with competitors allmost over thestudies world. This trend, main characteristics: thedemonstrate number of components andto(ii) the personalized medicine since, in cases, to each patient is The aim of this paper(i) is to a methodology create already given a specific treatment, with showing that The aim of this paper is to demonstrate a methodology to create already given a specific treatment, with studies showing that which is inducing the development from macro to micro type of components (e.g. mechanical, electrical, electronical). medical devices, using Additive Manufacturing (AM), coupled the relationship between the medical professional and patients medical devices, using Additive Manufacturing (AM), coupled the relationship between the treatment medical professional patients markets, results in diminished lot sizes due to augmenting Classical methodologies considering mainlywhich single products with other technologies such as 3D scanning, allows for has a positive impact on the outcome [4].and with other technologies such as 3D scanning, which allows for has a positive impact on the treatment outcome [4]. product varieties (high-volume to low-volume production) [1]. or solitary, already existing product families analyze the the virtual representation of the patient anatomy. With rehabilitation medicine being a multidisciplinary the virtual representation of thelevel patient anatomy. level) which Withthis rehabilitation medicine a multidisciplinary To cope with augmenting variety being as well as to be able to product structure on a physical (components identify in the existing causes difficulties regarding an efficient definition and 2212-8271 possible © 2019 The optimization Authors. Publishedpotentials by Elsevier B.V. 2212-8271 2019responsibility The it Authors. Published Elsevier B.V.of the Peer-review©under of the scientific committee CIRP Design Conference 2019 of different product families. Addressing this production system, is important tobyhave a precise knowledge comparison Peer-review under responsibility of the scientific committee of the CIRP Design Conference 2019

2212-8271©©2017 2019The The Authors. Published by Elsevier 2212-8271 Authors. Published by Elsevier B.V. B.V. Peer-review under responsibility of scientific the scientific committee theCIRP CIRP Design Conference 2019. Peer-review under responsibility of the committee of the of 28th Design Conference 2018. 10.1016/j.procir.2019.04.254

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This methodology uses the powerful combination of 3D scanning and additive manufacturing for the design, prototype and manufacture of true personalized P/O [5]–[7].

• Fitment of the prosthesis/Orthosis • Adjustment of the prosthesis/Orthosis The last 4 steps are iterative, since patient satisfaction and comfort are important for continued use of the P/O [20].

Furthermore, to demonstrate the applicability of the methodology two case studies are presented.

This protocol was successfully implemented in two case studies which shall be covered in the next section.

2. Additive Manufacturing and Orthotics/Prosthetics Additive manufacturing is a group of processes in which an object is constructed layer by layer from an initial CAD model. ASTM 52900 defines 7 families of processes: vat photopolymerization, powder bed fusion, binder jetting, material jetting, sheet lamination, material extrusion, and direct energy deposition [8]. In this work the process used is Fused Deposition Modelling (FDM) from the material extrusion family. FDM consists of the deposition of a fused material through a orifice or extruder through a set path, layer by layer until the object is complete [9]. AM has been extensively adopted by the medical industry, ranging from surgical planning, by providing a physical model of the operation area, training, and orthotics and prosthetics, among others [10]. This adoption rate is due to the ability of this method to provide a quick turn-around, compared to the traditional methods, in new, or improved parts, given that the ever changing nature of the human body, requires constant tweaking and adaptation of the P/O [11]. In traditional methods, show in Figure 1, the creation of a P/O involves the creation of a negative mold in plaster, so that then a positive mold of the contact surface between P/O and anatomy is correct. Then a test model is created to determine usability, and after adjustments the final P/O is created.

3. Case Studies 3.1. Orthotics The first test case was the development of an orthosis for a patient with spastic diplegic cerebral palsy. This condition is characterized by increased muscle tone, especially in the lower limbs, which promotes the adoption of incorrect postures. As time goes by this incorrect posture tends to cause muscular problems, which in the case of the patient in question, required surgery to lengthen the flexor muscle of the left knee. Although recovery includes physical therapy, to maintain muscle tone and correct gait, there is a probability that during the rest period, the leg adopts a posture that would again shorten the muscle. As such the protocol was applied to the development of a knee orthosis to maintain the correct posture during sleep, designed to provide the minimum amount of discomfort, and to be able to be placed and removed by the patient without outside intervention. The first step was the acquisition of the anatomical structure using a Zscanner 700 with the specifications shown in table 1. Table 1 – Zscanner 700 Specifications Weight

980 grams

Dimensions

160 × 260 × 210 mm

Sampling speed

18,000 measurements per second

When using AM, 3D scanning is a common method used to acquire stump external geometry [12]. CT scanning is another technology widely used [13]. Ct scanning has the advantage of 4D imaging and lower volumetric errors [14], but it requires a technician and expensive equipment. Furthermore, there has been a rapid advancement in 3d scanning technology, and it has become the most widely used technique [15]–[17].

Laser

Class II (eye safe)

Nº of cameras

2

XY accuracy

Up to 50 microns

Resolution

0.1 mm in Z

ISO

20 μm + 0.2 L/1000

Texture resolution

50–250 DPI

Figure 1 - Fabrication process for fitting a transfemoral prosthesis: a) negative b) positive mold, c) testing model, d) final part. Pictures taken 2.1. P/Omold manufacturing protocol at a rehabilitation hospital.

Depth of field

30 cm

The manufacturing protocol of an Orthosis/Prosthetic here presented, was adapted from traditional protocols (that does not involve AM) [18], based on Product Design And Development [19] and consists of the following steps: • Establishing patient needs • Transform those needs into metrics for evaluation of prototypes • 3D scanning of the anatomical member for reference • Cleanup of the acquired image to remove artifact during acquisition • Design of the P/O using the virtual member as reference • Fabrication of the Prosthesis/Orthosis prototype

The virtual limb was then cleaned of artifacts and completed using meshmixer. With the virtual limb loaded into a CAD software, the design and development of the first prototype proceeded, followed by 3d printing the design, and used by the patient to assess usability. The process is shown in figure 2.



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3.2. Prosthesis The second case study was the development of a prosthesis for an infant with upper limb congenital malformation. The malformation is a transversal disorder of the upper third of the right arm as seen in figure 4, which is one of the most common congenital limb disorders [21].

Figure 4 – Right forearm X-Ray of the patient Figure 2 – Manufacturing protocol steps

Each prototype went through an evaluation stage and lessons learned from the prototype was carried to the next prototype. In total 5 prototypes were developed (figure 3) with the final one meeting all the required needs and metrics established from the beginning. This test case was the first test of the developed protocol, and its results were promising, since the concept was accepted by both the patient, (citing comfort, ease of use, and a desire to keep using the concept) and health professionals (since the concept prevented knee adduction, and thus improve the patient outcome). One thing of note is that there are still tests to perform, to determine the orthosis durability, and ability to perform the necessary knee positioning long term.

Figure 3 – Prototypes with the major improvements in each step.

The use of prosthetics in infants is recommended in order to stimulate bimanual activities and body symmetry [22]–[24], and to reduce rejection rates of more complex prosthetics in the future [22], [24], [25]. The patient already had a prosthesis, but it was a dolls hand mounted on a cup for placement. In this case the approach was to use the left hand as a template for the prosthesis. The first step was the 3D scanning of the upper third of the right arm, in order to determine the anatomy where the prosthetic was to be attached, using the same 3d scanner as on the first test case. The only deviation was the acquisition of the virtual image of the left arm, since the hand is a complex anatomical feature, for which 3d scanning was unsuitable. As such a CT scan of the left arm was performed, and processed into a CAD file using the method proposed by Lopes et al. [26] (Figure 5).

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As the figure shows, the print suffered from layer displacement and the support structures damaged the surface of the Prosthesis. Furthermore, after support dissolution, NinjaFlex® layers presented some modifications, which affected the overall object appearance and structure. This version, although with problems in printing quality was delivered to the patient for testing. The printing quality was improved with another type of TPU, named FilaFlex™ without support. This filament showed good quality printing and some of the printing defects were corrected as shown in figure 8.

Figure 5- Pipeline for CT data processing

With the 3d scan a socket was created for the amputated limb, and then it was required to merge the socket with the CT scan of the opposite limb the process was made using blender and is shown in figure 6.

Figure 8 – Final print FilaFlex™

Figure 9 shows the patient with the cosmetic prosthesis in real life situations. Currently the patient is using the second version printed with FilaFlex™. The patient used prothesis every day for the last year with no reported medical issues. The device was well accepted, and the parents report that there is no rejection or even concern from the child to use the device in his day to day activities.

Figure 6 - Geometry alignment procedures: A: Photography importation. B: Voronoi and stump geometries alignment. C: Hand alignment.

The material chosen to use for prosthesis fabrication was from NinjaTek®. NinjaFlex™ is a thermoplastic polyurethane with an easy-to-feed texture, presenting great flexibility and longevity compared to non-polyurethane materials, as well as a higher abrasion resistance. NinjaFlex™ can suffer 660% elongation without wear or cracking. Its polyurethane composition allows for excellent vibration reduction, furthermore its quasi-elastomeric properties are important in minimizing any chance of the patient hurting itself on the prosthesis. Since printing with flexible material is more difficult and for testing with the patient a first prototype in white PLA was performed. With the successful test of the first prototype, a second one was printed with NinjaFlex™, using PVA (a soluble polymer) as support material. The final print is shown in figure 7.

Figure 7 – Final prototype NinjaFlex™-PVA

Figure 9 – A, B and C: Patient with the PLA cosmetic prosthesis in different activities.D: Patiernt with the NinjaFlex cosmetic prosthesis.

4. Conclusions The goal of this paper was to present a methodology for the design and development of Prosthesis and Orthosis for the medical industry, leveraging the tenets of personalized medicine to improve quality of life, and treatment outcomes in patients. To illustrate the methodology, two case studies using CAD/CAM techniques to fabricate an orthosis for a spastic diplegic cerebral palsy to aid in treatment and an aesthetic lower arm prosthetic for a two-year old patient are presented.



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The case studies differed in target, patient age, function, scope and materials used, and both cases can be considered a success. The methodology leverages CAD/CAM techniques allied with Additive Manufacturing and new materials in order to create personalized medical devices in many fields. Finally, it is possible to conclude that this methodology gives a high personalization level to the device, reducing rejection rates, while allowing for a fast turnaround of concepts, fast customization and fast changes to an existing device at a significant lower cost. The expectation is that continuing work with hospitals and rehabilitation centres, this methodology becomes widely adopted, thus allowing for greater access to personalized P/O.

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[15]

Acknowledgements This work was supported by FCT, through IDMEC, under LAETA, project UID/EMS/50022/2019. The first and second authors would like to thank the support of the FCT, through UNIDEMI, project UID/EMS/00667/2019.

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