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  • Published on: 7th September 2019
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Emily Patterson

Career Assignment Part 1

Part 1:The people who are responsible for designing, fabricating, and fitting prosthetics are known as prosthetists and are usually lumped in the same career grouping with orthotists. The difference between the two is that while prosthetists are trained to work with artificial limbs, orthotists are trained to work with medical supportive devices like braces. Even though they have this difference, an orthotist or prosthetist can choose to specialize in both areas or pick one. To be more descriptive on their job duties, prosthetists evaluate patients on their needs, take measurements, design the prosthetic, fabricate it or supervise technicians on its creation, and select the materials for the prosthetic(bls.gov,2015). Besides just creating an artificial limb, prosthetics teach their patient on how to use and care for the prosthetic and repair or replace older prosthetics. A prosthetist can work in an office where they meet with patients, in hospitals, or even in medical equipment and supplies manufacturing. But before you end up as a prosthetist in one of these work places, you have to go through a few academic steps. First, a bachelor degree is required in any discipline that meets the science and math prerequisites for an orthotics and prosthetics master’s program. After graduating with a respective bachelor’s degree, the next step is to get a master’s degree in orthotics and prosthetics since this is required of all prosthetists and orthotists. A master’s degree usually takes two years to complete and a master’s in orthotics and prosthetics involves a program with courses in “upper and lower extremity orthotics and prosthetics, spinal orthotics, and plastics and other materials used for fabrication” (www.bls.gov,2015). As of 2015, there are 13 orthotics and prosthetics programs accredited by the CAAHEP. After obtaining a master’s degree, prospective prosthetics must complete a residency that is accredited by the NCOPE. In these residencies that usually lasts a year (or two if you want to specialize in both orthotics and prosthetics), candidates gain clinical experience by providing “direct patient care under the supervision of a certified or licensed practitioner”( www.ncope.org). After completing a residency, a candidate can now become a practicing prosthetist! This statement reigns true for those who practice in states that don’t require a license. But, if the state you practice in does require a license, certification just usually requires completing an accredited master’s program, an accredited residency program, and passing three exams. The annual wage of a prosthetist is around $64,040. The job outlook for prosthetists is very good with a projected 23% employment growth from 2014-2024, which is must faster than average. One reason for why more prosthetists will be employed is that the baby boom created a large generation that will need prosthetics in their older age. Also, as more people get access to health insurance because of federal health insurance reform, this opens up more people who can seek solutions to their health issues, including prosthetics. Overall, the outlook for prosthetists is very bright and I like this occupation for the fact that it incorporates engineering techniques and helping others.

Part 2a: Prosthetics is a subdivision of biomechanics and because of the abrupt explosion of more complex technology; prosthetic research and advancements have been able to thrive.

1. Improving gait performance

Once an amputee receives a new lower limb, rehabilitation focuses mainly on restoring the ability to walk. Usually, an amputee receives prosthetic training by exercise, balance, and functional training in order to restore proper gait, or manner of walking. But, for this prosthetic training, there is no evidence-based best practice guideline for these therapists to use on amputees. Now, research is being done to scientifically test what practices are the best at improving gait performance of amputees. For example, professors at the Neurological Institute at Columbia University did research on how exercise programs affected gait performance in people with lower limb amputations. This was a systematic review so instead of conducting the experiment themselves, they found other researchers’ experiments pertaining to the topic and analyzed those results. Eight test groups were analyzed where a range of exercise programs were used; including supervised walking, specific muscle strengthening, balance training, part-to-whole gait training, and functional gait/activity(Wong et al.).. The gait speed of the participant was used as the measurement for gait performance and the results were vague and showed that all forms of exercise were able to improve the gait speed of the participants. Although this experiment did not reach finalized conclusions because of bias and only measuring one outcome, it shows and acknowledges that more extensive research should be done to see what practices improve gait performance the most.

2. Gait adaptations of transfemoral prosthesis

When a transfemoral amputee uses their prosthetic, “stability and confident gait is important for motility” and an amputee usually develops a dynamic stability for their movement(Kendall et al.). But, when an amputee feels unstable in their prosthetic, they can develop a protective gait pattern like slowing down that can adversely affect their gait. Dr. Cynthia Kendall and other associates did research on what gait adaptations transfemoral amputees have and how effective plantar-pressure and temporal measures are in measuring dynamic stability. For this experiment, the researchers used an F-Scan Mobile system which are plantar-pressure-sensing insoles with sensor cells on them that were put into each shoe of the 11 participants. The participants walked on different surfaces-hard, soft, ramped, and stairs and six plantar-pressure and temporal measures were collected from the sensors. The results showed that the majority of the participants had irregular progression in the anterior-posterior and medial-lateral direction and “repeated loading of a local foot region” which indicate increasing instability(Kendall et al.). Comparisons of these measures on the different limbs showed that the amputees rely on the intact limb to stabilize them and used it as a propulsion engine. These results and research can help prosthetists with fit and alignment of prosthetics and shows that the plantar-pressure sensors in the soles are a viable, noninvasive, and convenient way of evaluating motility of amputees.

3. Biocompatibility

Biocompatibility involves biomaterials having to be compatible with living tissue by not being toxic or causing rejection. This area is starting to become relevant in prosthetics since researchers are trying to find a way to connect the prosthetic to the nervous system. Currently, there are no devices that can connect the two but researchers at the Sandia National Laboratories are trying to do just that- design biocompatible interface scaffolds that that help an amputee control their prosthetic with their own nervous system. This discovery could give back some sense of touch, though not directly through the prosthetic arm or hand, and make it easier for a prosthetic to be controlled. These interface scaffolds would allow transected nerves to grow, “putting small groups of nerve fibers in close contact to electrode sites connected to separate, implanted electronics”(Holmes). Basically, these interfaces can provide inputs to let amputees control their prosthetic by direct neural signals. But, the problem lies in finding a material for these interfaces that are biocompatible to the nerve fibers so that nerve bundles can be integrated and manage to not harm the nervous system. The group of researchers actually developed two polymers, PBF and PDMS, that are both biocompatible but both substrates ended up being too thick for the nerves to penetrate the scaffolds. Now, different techniques that have been around for a while are being used; like projection microstereolithography- where they “use the magnifying glass to focus UV light onto the PDMS-coated silicon wafer to form thin porous membranes”(Holmes). With this technique, the researchers are now one step closer to creating the right biocompatible, useful polymer for these interfaces.

4. Distributed Sensors for Prosthetic Sockets

The comfort of the amputee’s limb when in a prosthetic socket is very important since most of their life is spent in a prosthetic. Unfortunately, static prosthetic devices can become uncomfortable since the limb of the amputee can change over time. Also, many other factors like temperature, moisture, stress, and pressure can cause discomfort in the form of blisters and skin or tissue damage. Luckily, researchers at the National Institute of Health are designing a new class of prosthetics that will conform to the human body and manage other factors like the temperature. These researchers are using pressure, shear stress, and temperature measuring sensor arrays, which are “fabricated upon a flexible and stretchable substrate” to give details of these factors in the prosthetic interface(Mamishev et al). By using these sensors on different sockets and suspensions, researchers can analyze which design structure is best at controlling all of these factors that can lead to uncomfortable amputee limbs.

5. Artificial legs that emulate healthy legs

Currently, many of the lower-limb prosthetics used are passive prosthetics that aren’t controlled by electricity or neurons. But, Professor Michael Goldfarb is on his way to developing a robotic leg “that can duplicate the natural movement of human legs”(Salisbury). This robotic leg would be able to drastically improve the mobility of lower-limb amputees, especially on stairs and slopes, which is where most lower-limb amputees fall. Goldfarb has already developed the first robotic prosthesis, which has powered knees, ankle joints, and a neural interface allowing leg movement controlled by thought. All of these components were possible because of technological advances like lithium-ion batteries (which store more electricity), powerful electric motors, and miniature sensors that play a key role in neural interfaces. With the development of this robotic leg, amputees would be able to walk faster, fall less, and overall have a more normal life with a leg that is basically their own again. Currently, the robotic leg is set behind because it still has yet to been approved by the FDA and clinicians would need to be more informed in robotics before helping those with robotic legs in rehabilitation.

6. Lower-limb prosthetics

Lower-limb prosthetics is a large area of study considering there can always be improvements for an artificial limb that is responsible for motion, balance, and overall support. Currently, the US Department of Veterans Affairs Limb Loss Prevention and Prosthetic Engineering Unit is focusing on “improving patient mobility and comfort and preventing injury”( CoE for Limb Loss Prevention and Prosthetic Engineering).  For example, in order to combat fatigue and asymmetrical gait, researchers are testing varying stiffness of the prosthetic feet to see if stiffness can affect gait. Also, these researchers are trying to find a way to improve the mobility of lower-limb amputees, pertaining to turning corners and maneuvering around obstacles. One method they are testing is to see if a compliant torque adapter in the pylons of transtibial amputees is effective in helping maneuver around corners and obstacles. Another problem for lower-limb amputees is that their residual limb can overheat in the socket if there is a lot of activity since the socket and liners are good insulators. So, researchers are trying to develop an active cooling system with embedded sensors that can monitor skin temperature.

7.  Neural Prosthetic

As more success is being reached with prosthetics that can restore a sense that was once lost, like retinal and cochlear prostheses, neuroscientists want to take it a step further. Neuroscientists are looking to create neural prosthetics that will help epileptics, people with depression and chronic pain, Alzheimer’s patients, PTSD victims, and “individuals who have sustained spinal cord injury and loss of limbs”( Varrasi). The idea is to create devices that can read electrical and chemical signals from the nervous system to stimulate capability and restore quality of life. But, the setback is coming up with a material for the interfaces and devices that can sustain electrical function in the harsh environment of the body without hurting the tissue involved. Researchers at Lawrence Livermore National Laboratory have been making strides by making a thin-film flexible polymer to surround the neural interface and microelectrodes. These researchers tested these polymer-covered microelectrodes in auditory prosthetics and found that the device was able to move naturally and conform to live tissue. Overall, most of the efforts for neural prosthetics are finding materials for the devices that will be biocompatible with the tissue and nerves and also be functional.

8. Self-healing electronic skin

Research is being done to create a material for the outside of prosthetics that can mimic the pressure sensitivity and self-healing processes of human skin. Professor Tee and other associates have created a material that has “mechanical and electrical self-healing properties at ambient conditions”(Tee at el.) Also, the material was found to be pressure and flexion sensitive just like human skin. Results showed that after being ruptured, the initial conductivity was restored after 15 seconds of healing time and the mechanical properties were completely restored after 10 minutes of healing time. These results help show that electronic skin systems like the material made by Tee are effective at self-healing and can be used like human skin for prosthetics

9. Sensory-feedback electronic skin

Human skin has an array of sensors that feel for us and provide feedback to our nerves to help us “avoid a hot object or increase the strength of our grip on an object that may be slipping away”(Tee et al.). Now, researchers like Professor Tee are being inspired by human skin to create an artificial mechanoreceptor that can mimic the sensory feedback of human skin. Tee and other associates developed a power-efficient mechanoreceptor with a flexible organic transistor circuit that can convert pressure into digital frequency signals directly. These frequency signals were used to stimulate mouse neurons and achieved stimulated pulses in cue with pressure levels. This research and development of this mechanoreceptor shows a step forward in designing an electronic skin with touch (sensory feedback) for prosthetic limbs.

10. Argus II Retinal Prosthesis System

Prosthetic eyes have been around for a fairly long time and have all achieved the function of filling in the space of the previous eye and slightly restoring vision. But now, researchers are focusing on creating retinal prosthetics that can majorly/fully restore the blind/lost eye’s function. Dr. Ho and many other doctors and professors worked together to develop the Argus II Retinal Prosthesis System which is the first retinal implant/prosthetic to be approved by the FDA and receive a CE mark in Europe. This prosthetic system consists of an active device implanted on and in the eye that works in conjunction with a glasses-mounted video camera and small video processing unit. This system works by the camera collecting images that are sent to the VPU, the VPU processes the image and sends the data to the internal receiving antenna which sends out electricity corresponding to the brightness of the image. This then stimulates the remaining retinal cells and causes cellular responses in the visual system, “resulting in visual percepts that subjects learned to interpret”(Ho et al.). An experiment was done testing the effectiveness of this system, and results showed that 29 of the 30 participants who were completely blind in one eye because of Retinitis pigmentosa had functioning systems after 3 years and overall, participants performed significantly better with the system in visual function tests. Even though only some visual function was restored for these participants, the Argus System shows that restoring a sense that was once lost is possible, even if it is not completely restored.

Part 2b:Technical Trends

For current research being done on prosthetics, there are definite trends that exist and seem to coincide with each other. As more advancement is being made in this area, researchers can expand their work into areas that were never considered before.

One trend that I observed through my research is that of focusing more on the individual wearing the prosthetic and taking their abilities into account. When prosthetics were first being used commercially, the main focus was just about giving a person a limb so that they can walk, however uncomfortable or awkward it may be. But since the basics and mechanics of prosthetics are covered now, today’s prosthetics and research focus on improving the comfort of the amputee. For instance, the scientists at the National Institute of Health are working to develop prosthetics that conform to the human body and control temperature making the prosthetic more comfortable for the user. Also, researchers at the US Department of Veterans Affairs are testing to see if the stiffness of the prosthetic feet could affect the amount of fatigue on the amputee.

Another trend that is evident in the above summaries is the use of sensors in prosthetics as a measurement tool. Because of advancements in technology, researchers can now incorporate this technology into the prosthetics. For example, Dr. Kendall was able to use sensor cells in insoles to effectively measure the irregularities of amputees’ gait. Also, researchers at the National Institute of Health are using an array of sensors to test what sockets and suspensions are best at controlling temperature, shear stress, and pressure. Not only are these sensors being used as measuring tools, but also they are being utilized at components of prosthetic designs. Professor Tee is using a version of sensors, mechanoreceptors, to effectively convert pressure to frequency signals and achieve sensory feedback.

A trend that I noticed being mentioned in some sources is the focus on biocompatibility when creating prosthetics. As prosthetics makes a transition from being just external artificial limbs to internal prosthetics like neural prosthetics, biocompatibility is an important factor.  Neuroscientists have to make sure that the devices to be used as neural prosthetics are compatible to tissue but still functional. Also, neural interfaces that work with prosthetics must be able to match the composition of nerves and allow nerve growth without losing it electrical ability.

The broadest trend I noticed among almost all of the sources is the focus on helping the amputee regain the most amount of normal human ability as they can. Creations like the Argus System and sensory feedback electronic skin achieve bringing back senses (partially/fully) to the amputee that they lost. This puts them one step closer to having full human function. Also, the robotic leg and improvements on lower-limb prosthetics achieve making prosthetics function in a way very close to that of an actual human leg.

Overall, all of these trends seem to work together and have coexistence among them. By focusing more on the amputee, researchers started to focus on restoring as many human like abilities as possible back to the amputee. As this became a focus, biocompatibility became relevant since new devices that restored human senses needed to be incorporated and compatible with tissues and nerves inside the body. Alao, sensors are able to help researchers see what devices work and help make some human senses come back to life.

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