Prosthesis Materials Evaluation - Report Example

Executive summary An increasing number of people are undergoing limb loss leading to projected rise of prostheses demand across the globe. While great strides have been made in the science of prosthetic limb making, limbs that are available in the market today are still incapable of satisfying the functional, comfort and aesthetic needs of most users. Indeed, numerous factors impact end user satisfaction, but it is limb design and material choice that are at the elementary end of this spectrum. Numerous materials have been tested in the history of prostheses making. More continue to be discovered. A comprehensive understanding of the suitability of different materials in the making of the different components of prosthetic limbs is therefore needful. The purpose of this study is to interrogate the suitability of an assortment of eleven materials in the manufacture of below the knee prosthetic limbs firstly, for day-to-day use and secondly, for use during a lunar expedition. The physical properties that will be of concern to this study are compressive strength, fatigue resistance, rigidity, corrosion resistance, density/weight, comfort, non-reactive to skin/body, working temperature, colour, durability, recyclability and environmental impact of the procedure of processing each material. Introduction The increased need for prostheses has made it necessary to have a better understanding of not only the best materials to use in highly specific contexts but also the most efficient and environmental friendly manufacturing processes to be used to produce them. Sustained overall improvement of quality and access of health care across the globe has resulted in higher life expectancy and aging populations thus raising the necessity for more medical procedures involving prostheses and medical implants (Nag and Banerjee, 2012). There are approximately two million people living with limb loss in the United States today (AmputeeCoalition.Org, 2017). These figures are anticipated to rise to approximately 3.6 million by the year 2050 largely due to the projected increase in the prevalence of dysvascular diseases as well as due to the effects of a gradually aging population (Ziegler-Graham et al., 2008). These figures signify the progressive significance of prosthetic limbs in ensuring functional lived experiences for people living with limb loss. Indeed, prosthetic limbs offer the only possibility for potential restoration of pre-amputation quality of life such as reinstatement of employment (Raichle et al., 2008). This study intends to explore the most suitable material for the manufacture of below the knee lower prosthetic limbs firstly, for everyday use and secondly, for a polar expedition. Below Knee Prosthetics In spite of their obvious benefits, the uptake of prosthetic limbs amongst people living with limb loss continues to be hindered by a number of factors. Prosthesis use and satisfaction have a close connection with factors relating to the design and the material used to make the prosthesis (Webster et al., 2012). Among these factors, it is cost, comfort, durability and functionality of the prostheses that have had an enduring bearing on the choice of material the artificial limbs are made of. These factors affect not only the initial adoption of prosthesis use but also the consistency of their use over time (Webster et al., 2012). Studies have indeed shown that even in situations where there has been consistent prostheses use, a majority of users were dissatisfied with the comfort of the prostheses (Dillingham et al., 2001). While a wide range of materials have been tested in the design of lower extremity prosthetic limbs, an ideal one has yet to be settled on in light of the myriad physical and mechanical properties that have to be considered. Additionally, the choice of material also depends on whether the limb is designed for general function or specialized use such as dancing or skiing. Moreover, the outward appearance of the limb does influence the choice of material especially if the limb is meant for everyday use. In fact, the physical appearance of the prosthetic limb greatly influences not only the acceptability of the limb to the user but also the user’s self-image as well as his or her psychological adjustment towards the appendage (Sansoni et al., 2015). Whether the user finds the limb acceptable in turn hinders or promotes its overall usefulness. Indeed, a limb’s aesthetic appeal seems to matter as much as comfort and functionality to amputees (Sansoni et al., 2015). For these reasons, material choice is a matter of great consequence in the design of prosthetic limbs. The functionality and comfort of lower extremity prosthetic limbs is hugely affected by its weight. Heavier limbs require more energy to propel through the air in the swing phase of the prosthetic gait (Mattes, 2014). This results in asymmetry in the walking patterns between the prosthesis and the intact limb (Mattes, 2014). Indeed, heavier limbs are also much more likely to result in sores at the point of contact with the residual limb (Mittal et al., 2009). While limbs that are lighter than the natural limb are easier to put on and take off and portend a healthier residual limb (Mittal et al., 2009), they however may make the user feel less in control of the artificial limb. Data on weight preference by lower extremity prosthetic limb users remains ambivalent as partiality for lighter as well as heavier limbs by end users has been found to be evenly distributed in varying studies (Mattes, 2014). Striking a balance between these mass considerations therefore in the design and material choice of the limb is of utmost significance. Great advances have been made in material choice in prosthetic limbs. The continued discovery of lighter and more versatile materials such as alloys and thermoplastics have had a great impact in the design of prostheses (Metzger, 2006). The entry of thermoplastics, thermosetting materials, foamed plastics and viscoelastic polymers has meant lighter, more versatile and more durable choice materials for prostheses design (Ramos, 2015). These material have also made the fabrication of the customized parts of prostheses easier leading to limbs that are more suited to individual user’s needs. Prosthetic limbs were originally meant for disguising deformity and were therefore nonfunctioning (Mittal et al., 2009). With technological advancement however, this function evolved to the restoration of the functionality of the lost limb. With time however, mere functionality of the limb was no longer sufficient as users increasingly required prosthetic limbs that resembled their natural limbs as closely as possible. Aesthetic considerations have therefore come to impact on material choice for prosthetic limbs (Sansoni, et al., 2015). As such, materials that offer increased pigmentation choices as well as those whose texture closely resemble human skin have been found to be more preferable as exoskeletal covers of prosthetic limbs among limb loss victims. In this regard, polyurethane and PE foams have been adopted to provide the outer cover of prostheses in order to give them a more life-like appearance (Metzger, 2006). With the availability of a wide range of materials with varied physical and mechanical properties becoming a reality, different parts of prosthetic limbs are nowadays made different materials depending on the function of the part, properties of the material as well as the cost of the material. Components such as the socket, joints, terminal devices and suspension all require material with highly specified properties. The environment of use of lower extremity prosthetic limbs should also be put into consideration during the design stage. For instance, wet or moist environments would require that that the materials chosen be water resistant. The prosthetic limb user’s lifestyle ought also to affect the choice of material. Users who spend a lot of time on their feet or whose occupations involve ascending and descending inclining surfaces should wear prosthetics that are adopted to such lifestyles. The materials to be considered are carbon fibre, polyamide (PA) nylon, polyethylene (HDPE), titanium, aluminium, acrylic nitrile butadiene, polypropylene, glass filled polyamide, polyurethane, MULYI polymer 3D print and stainless steel. The physical and mechanical properties that will be of special interest to this study are compressive strength, fatigue resistance, rigidity, corrosion resistance, density/weight, comfort, non-reactive to skin/body, working temperature, colour, durability, recyclability and environment impact. Manufacture Materials Carbon fibre Carbon technology has been incorporated in the recent years in the field of prosthetic and orthotics due to numerous benefits that comes with it, majorly because it has less weight compared to traditional materials (Klute et al., 2001). This makes it comfortable for the patients by reducing strain and stress that might result from carrying heavy materials. Carbon materials are also preferred since it is durable both in daily use and in polar expeditions. This minimizes cost of replacing the products. Carbon is also strong and flexible (Klute et al., 2001). This ensures ease of turning and movement without causing harm to the patients’ skin and soft limb tissues. One common effect of carbon to the environment is high level of pollution caused by improper routes of its extraction and product manufacture. If proper measures are not followed, carbon (IV) oxide emission can cause global warming due to greenhouse effects. To minimize such effects, proper techniques processing methods have been employed in modern clinical practices. This includes laying down measures to curb on pollution and to minimize cost. Caron fiber is therefore suitable for both polar expedition and for everyday use in prosthetic manufacture. Polyamide (PA) Polyamide (PA) nylon is another material used in the manufacture of prosthesis. PA possesses the following physical properties that make it suitable for the process. It is tough, strong and resistance to high temperature, bases and abrasion (Nag and Banerjee, 2012). These properties make PA a good material for prosthesis since its products are durable and this minimizes cost. In addition, its nature to resist solvent ensures a comfortable environment of the patients limp stamp. PA has got a low coefficient of friction. This ensures less harm and pain to the limb skin and tissues during walking and turning. Nevertheless, PA has a very high ability to absorb moisture which affects its mechanical and electrical properties. It also shrinks very fast especially when poorly processed. PA is also known to be affected by most oxidizing agents and strong acids. Due to these facts, PA is commonly used in everyday use prosthesis but not suitable for polar expedition purposes (Nag and Banerjee, 2012). Polyethylene (HDPE) Polyamide (HDPE) is another materials used in clinical prosthesis especially in the manufacture of limb sockets. It is can be reused through recycling. This minimizes possible costs incurred. HDPE is also durable since it non-biodegradable, it has a low density hence easy to use as it reduces stress on movement. Its waterproof nature makes it comfortable as it does not favor breeding of fungal infections (García-Gareta et al., 2015). One disadvantage of using polyethylene is its sustainability since it is derived from crude oil, a non renewable source of energy. HDPE wears out very first where small debris peels off gradually especially when exposed to extreme changes of moisture and high temperatures. It is also affected by strong acidic conditions. On environmental effects, during its extraction through combustion it produces carbon (IV) oxide which is a greenhouse gas that leads to global warming. Titanium Titanium is another useful metal that is commonly used in prosthesis due to its rigid nature, can be used in places that require more hard tissues, it is very strong and tough for long-term use. All these characteristics enable it to withstand extreme weather conditions such as high temperature, precipitation and extreme pressure (Jemat et al., 2015). Due to its strength, titanium is able to hold more weight without experiencing critical stress and tensile. Nevertheless, its longevity is not certain though believed to last for a decade. Another demerit of titanium is that it has poor compatibility with bones for longer period of usage compared to other materials. This makes it costly and dangerous during corrective surgery to replace devices made of it. Otherwise, it is not affected by most substances or weather factors hence can be used in both daily usage or in polar expedition. One common disadvantage of titanium devices is within the area of implant. For instance, the body can react with it hence affecting its performance due to inflammations that accompanies it and that can lead to fibrosis. Aluminum Aluminum prosthesis is also commonly used in clinical fields in patients requiring limb fixation. Aluminum is a strong metal that is nonferrous. It has a high boiling and melting point hence can withstand high temperatures. It has high density compared to other materials used making strong and durable. Its silvery shinny colour makes it more attractive (Nag and Banerjee, 2012). Devices made of aluminum are not affected by many substances such as extreme weather conditions such as precipitation, temperature and even atmospheric pressure. This enables it to be used in everyday prosthesis and that of polar expedition. Stainless steel Stainless steel is another commonly used metal globally. Just like aluminum, it is also used in the manufacture of prosthesis in the medical field. It is easy to fabricate stainless steel in different forms and designs and also it is a cheap metal which is readily available (abrasion (Nag and Banerjee, 2012). To achieve effective mechanical characteristics of the metal, proper treatment during its extraction should be done. This includes among others; removal of impurities, thermal treatment and even making desired alloys depending on the intended use. In some cases, stainless steel can be electroplated using less corrosive metals such us nickel or chromium to improve on its physical appearance. This makes it even stronger and non-corrosive to the body tissues of the patient. Stainless steel is a very hygienic material since it is easy to clean, it is also cheap to obtain. Different alloys of steel are also known to resist varied temperatures and corrosion depending on the alloy mixture. Another factor that determines its choice for use is its durability and its ability to exist in different appearances hence pleasant. For these reasons, it can be used mostly in both daily and polar expedition since it can withstand conditions existing in both conditions. PU (Polyurethane) Polyurethane has also been used due to its affordability, high resistance to abrasion effects and even ability to exist in a range of variety in terms of structure (Gradinaru et al., 2012). In addition, it can do well under low temperatures hence good for polar expedition prosthesis. It is affected by numerous organic solvents and it does not do well in regions experiencing direct sunlight rays. Depending on choice and intended purposes, it comes in two major categories i.e. polyether type and polyester type. It should be noted that PU has some demerits. For instance, it is flammable, affected by many solvents, cannot withstand extreme weather conditions and also inability to withstand high temperatures (Gradinaru et al., 2012). Due to these reasons, it is less used in both everyday use and polar expedition prosthesis. Acrylic nitrile butadiene (ABS) ABS is known for its numerous functional and workable qualities. Among them, there is essence of ability to resist impact, heat, bases and acids. It is also easy to work with it since it can be fabricated into various forms very easily. In addition, it is a multipurpose material that can be used in manufacturing a variety of products. Due to moderate strength and ability to resist impact, it is widely used since it ensures no tress and pain is spread on the tissues of a patient. Also, it minimizes cost through durability due to less replacement processes (Nag and Banerjee, 2012). ABS exhibits some demerits that might hinder it from being used in all weather conditions. For instance, it lowly resists heat making it unsuitable in hot regions; it does not also fully resist most chemical components and thermal effects. It also reacts with body regions and is likely to form bubbles and even create voids. ABS in also very expensive compared to other forms of materials. Its inability to resist moisture makes it less suitable for use in polar expedition prosthesis. Polypropylene (PP) With the aid of a suitable catalyst, polypropylene can be derived from polymerization of propylene. Its properties such as low density of about 0.905g/cm3 make it suitable in manufacture of prosthesis due to reduced weight. Compared to polyethylene, PP can withstand high temperature and is also strong due to its structural composition. Its molecular composition depends on the nature of its monomers and production techniques. It is also stiff with high impact resistance. This ensures reduced stress due to load of the patients’ body trunk (Nag and Banerjee, 2012). Some disadvantages of PP include; it does not easily bond with bone tissues, it is flammable, when exposed to aromatics and UV it is often affected. PP can therefore be used to a small extent in daily and in polar expedition prosthesis. Glass filled polyamide (PAGF) (PAGF) is characterized by high temperature, impact and abrasion resistance. It is also resistance to chemicals such as bases. Its toughness and medium strength makes it to be used in this field. Many companies that deal in it have admitted the material to be easily processed especially through thermoplastic techniques. In addition, its reduced friction coefficient makes it suitable in manufacturing different designs of prosthesis (Nag and Banerjee, 2012). Its ability to absorb moisture makes it unsuitable in polar expedition devices since it cannot be easily worn out by moisture. Since PAGF needs UV in order to stabilize it, it might not be used in polar regions that experiences low UV exposure per given day. Moisture, oxidizing agents and phenols also affects its mechanical traits. When exposed to all these factors, it tends to shrink hence influencing its workability. MULYI polymer 3D print This is a technology that allows manufacture process of prosthetics using a combination of various materials through 3D printing. This is the most current innovation in manufacture of realistic looking prototypes and will be the one most recommended for manufacture of the prosthetic limbs. REPORT & ANALYSIS: Material grading criteria Criterion for grading materials is based on a number of factors concerning different materials and their preferred use. First, activity level in considered. Activity of an individual will determine the strength of the material to be used. For instance, sports persons will require tougher and stronger materials than individuals who spend most of their time indoors. Secondly, cost of the material is considered. Other factors to note include aspects of weather, expected weight of individuals, and even suspensions. In addition, unique characteristics such as resistance to salt, base or acidic corrosion can at times be considered. In many cases, components of prosthetic are considered such as activities of the individual and even their total body weight. 1. Material:Carbon fibre Requirement Polar Day Compressive strength 3 3 Fatigue resistance 1 1 Rigidity 1 1 Corrosion resistance 3 3 Density / weight 3 3 Comfort 1 1 Non-reactive to skin/body 3 3 Working temperature 1 1 Colour 1 1 Durability 1 1 2. Material:Polyamide (PA) nylon Requirement Polar Day Compressive strength 1 1 Fatigue resistance 1 1 Rigidity 1 1 Corrosion resistance 1 1 Density / weight 1 1 Comfort 1 1 Non-reactive to skin/body 1 1 Working temperature 1 1 Colour 1 1 Durability 1 1 3. Material:Polyethylene (HDPE) Requirement Polar Day Compressive strength 1 1 Fatigue resistance 1 1 Rigidity 1 1 Corrosion resistance 1 1 Density / weight 1 1 Comfort 1 1 Non-reactive to skin/body 1 1 Working temperature 1 1 Colour 1 1 Durability 1 1 4. Material:Titanium Requirement Polar Day Compressive strength 1 1 Fatigue resistance 1 1 Rigidity 1 1 Corrosion resistance 1 1 Density / weight 1 1 Comfort 0 0 Non-reactive to skin/body 0 0 Working temperature 1 1 Colour 1 1 Durability 1 1 5. Material:6082 aluminium Requirement Polar Day Compressive strength 3 3 Fatigue resistance 1 1 Rigidity 1 1 Corrosion resistance 3 3 Density / weight 1 1 Comfort 1 1 Non-reactive to skin/body 1 1 Working temperature 3 3 Colour 3 3 Durability 3 3 6. Material:Acrylic nitrile butadiene (ABS) Requirement Polar Day Compressive strength 1 1 Fatigue resistance 1 1 Rigidity 1 1 Corrosion resistance 1 1 Density / weight 1 1 Comfort 1 1 Non-reactive to skin/body 1 1 Working temperature 1 1 Colour 1 1 Durability 1 1 7. Material:Poly propylene (PP) Requirement Polar Day Compressive strength 1 1 Fatigue resistance 1 1 Rigidity 1 1 Corrosion resistance 1 1 Density / weight 1 1 Comfort 1 1 Non-reactive to skin/body 1 1 Working temperature 1 1 Colour 1 1 Durability 1 1 8. Material:Glass filled polyamide(PAGF)nylon Requirement Polar Day Compressive strength 1 1 Fatigue resistance 1 1 Rigidity 3 3 Corrosion resistance 1 1 Density / weight 3 3 Comfort 3 3 Non-reactive to skin/body 3 3 Working temperature 1 1 Colour 1 1 Durability 1 1 9. Material:Polyurethane (PU) Requirement Polar Day Compressive strength 1 1 Fatigue resistance 1 1 Rigidity 1 1 Corrosion resistance 3 3 Density / weight 3 3 Comfort 3 3 Non-reactive to skin/body 3 3 Working temperature 1 1 Colour 1 1 Durability 1 1 10. Material:MULYI polymer 3D print Requirement Polar Day Compressive strength Fatigue resistance Rigidity Corrosion resistance Density / weight Comfort Non-reactive to skin/body Working temperature Colour Durability 11. Material:Stainless steel Requirement Polar Day Compressive strength 1 1 Fatigue resistance 1 1 Rigidity 3 3 Corrosion resistance 3 3 Density / weight 1 1 Comfort 1 1 Non-reactive to skin/body 1 1 Working temperature 1 1 Colour 1 1 Durability 3 1 Excellent 3 Good 1 Okay 1 Not suitable 0 Conclusion This concludes that material choice for prosthetic limbs is a balancing act due to the many concessions that one has to make. The unavailability of an ideal fit-all material raises the need to adopt different materials for the different components of the limb while still considering the intended use of the limb as well as the environment in which it will be used. Further research is recommended for the best materials for different components even as more composites and alloys are being discovered. References AmputeeCoalition.Org, 2017. Limb Loss Statistics. [Online] Available at: http://www.amputee-coalition.org/limb-loss-resource-center/resources-by-topic/limb-loss-statistics/limb-loss-statistics/#.WRH0RVWGPIU Dillingham , T. R., Pezzin , L. E., MacKenzie, E. J. & Burgess, A. A., 2001. Use and satisfaction with prosthetic devices among persons with trauma-related amputations: a long-term outcome study. Am J Phys Med Rehabil, 80(8), p. 563–571. García-Gareta, E., Coathup, M.J. and Blunn, G.W., 2015. Osteoinduction of bone grafting materials for bone repair and regeneration. Bone, 81, pp.112-121. Gradinaru, L.M., Ciobanu, C., Vlad, S., Bercea, M. and Popa, M., 2012. Thermoreversible poly (isopropyl lactate diol)-based polyurethane hydrogels: effect of isocyanate on some physical properties. Industrial & Engineering Chemistry Research, 51(38), pp.12344-12354. Jemat, A., Ghazali, M.J., Razali, M. and Otsuka, Y., 2015. Surface modifications and their effects on titanium dental implants. BioMed research international, 2015. Klute, G. K., Kallfelz, C. F. & Czerniecki, J. M., 2001. Mechanical Properties of Prosthetic Limbs: Adapting to the Patient. Journal of Rehabilitation Research and Development, May/June, 38(3), p. 299–307. Mattes, S., 2014. Is Lighter Better? Thoughts on the Relationship between Device Weight and Function. The O&P Edge, May. Metzger, S., 2006. Materials Science: Producing Lighter, More Cosmetically Appealing O&P Devices. The O&P EDGE, August . Mittal, A., Srikanth, G. & Biswas, S., 2009. Composite Materials for Orthopaedic Aids. TIFAC. Nag, S. & Banerjee, R., 2012. Fundamentals of Medical Implant Materials. ASM Handbook, pp. 6-16. Raichle, K. A. et al., 2008. Prosthesis Use in Persons with Lower- and Upper-Limb Amputation. Journal of Rehabilitation Research & Development, 45(7), p. 961–972. Ramos, V., 2015. Introduction to Prosthetic Limbs. The Kabod, 2(1). Sansoni, S., Wodehouse, A., McFadyen , A. & Buis, A., 2015. The Aesthetic Appeal of Prosthetic Limbs and the Uncanny Valley: The Role of Personal Characteristics in Attraction. International Journal of Design, 9(1), pp. 67-81. Sanbhal, N., Miao, L., Xu, R., Khatri, A. and Wang, L., 2017. Physical structure and mechanical properties of knitted hernia mesh materials: A review. Journal of Industrial Textiles, p.1528083717690613. Webster, J. B. et al., 2012. Prosthetic fitting, use, and satisfaction following lower-limb amputation: A prospective study. JRRD, 49(10), p. 1493–1504. Ziegler-Graham, K. et al., 2008. Estimating the Prevalence of Limb Loss in the United States: 2005 to 2050. Archives of Physical Mecine and Rehabilitation, March, 89(3), p. 422–429. Read More

Among these factors, it is cost, comfort, durability and functionality of the prostheses that have had an enduring bearing on the choice of material the artificial limbs are made of. These factors affect not only the initial adoption of prosthesis use but also the consistency of their use over time (Webster et al., 2012). Studies have indeed shown that even in situations where there has been consistent prostheses use, a majority of users were dissatisfied with the comfort of the prostheses (Dillingham et al., 2001). While a wide range of materials have been tested in the design of lower extremity prosthetic limbs, an ideal one has yet to be settled on in light of the myriad physical and mechanical properties that have to be considered.

Additionally, the choice of material also depends on whether the limb is designed for general function or specialized use such as dancing or skiing. Moreover, the outward appearance of the limb does influence the choice of material especially if the limb is meant for everyday use. In fact, the physical appearance of the prosthetic limb greatly influences not only the acceptability of the limb to the user but also the user’s self-image as well as his or her psychological adjustment towards the appendage (Sansoni et al., 2015). Whether the user finds the limb acceptable in turn hinders or promotes its overall usefulness.

Indeed, a limb’s aesthetic appeal seems to matter as much as comfort and functionality to amputees (Sansoni et al., 2015). For these reasons, material choice is a matter of great consequence in the design of prosthetic limbs. The functionality and comfort of lower extremity prosthetic limbs is hugely affected by its weight. Heavier limbs require more energy to propel through the air in the swing phase of the prosthetic gait (Mattes, 2014). This results in asymmetry in the walking patterns between the prosthesis and the intact limb (Mattes, 2014).

Indeed, heavier limbs are also much more likely to result in sores at the point of contact with the residual limb (Mittal et al., 2009). While limbs that are lighter than the natural limb are easier to put on and take off and portend a healthier residual limb (Mittal et al., 2009), they however may make the user feel less in control of the artificial limb. Data on weight preference by lower extremity prosthetic limb users remains ambivalent as partiality for lighter as well as heavier limbs by end users has been found to be evenly distributed in varying studies (Mattes, 2014).

Striking a balance between these mass considerations therefore in the design and material choice of the limb is of utmost significance. Great advances have been made in material choice in prosthetic limbs. The continued discovery of lighter and more versatile materials such as alloys and thermoplastics have had a great impact in the design of prostheses (Metzger, 2006). The entry of thermoplastics, thermosetting materials, foamed plastics and viscoelastic polymers has meant lighter, more versatile and more durable choice materials for prostheses design (Ramos, 2015).

These material have also made the fabrication of the customized parts of prostheses easier leading to limbs that are more suited to individual user’s needs. Prosthetic limbs were originally meant for disguising deformity and were therefore nonfunctioning (Mittal et al., 2009). With technological advancement however, this function evolved to the restoration of the functionality of the lost limb. With time however, mere functionality of the limb was no longer sufficient as users increasingly required prosthetic limbs that resembled their natural limbs as closely as possible.

Aesthetic considerations have therefore come to impact on material choice for prosthetic limbs (Sansoni, et al., 2015). As such, materials that offer increased pigmentation choices as well as those whose texture closely resemble human skin have been found to be more preferable as exoskeletal covers of prosthetic limbs among limb loss victims.

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