Advances in Prosthetic Technology

[Music] my name is Mathew Garibaldi Richard is really leading this section he's our clinical chief at the orthopaedic Institute it sounds like some of you may know him Richard Egan and he comes to UCSF with a great deal of a private practice experience in the private sector and quite frankly is probably one of the most creative clinicians I've ever come across so he'll have a lot to offer tonight no excuse me and he's also chairs or runs our technology and innovation committee for OMP so he's the appropriate person to be speaking and I'll jump in here and there and give a couple thoughts on knees and upper extremity as well so without further ado I'll hand this over to Richard Ian Thank You Matthew all right good evening guys thanks for coming like Matthew said I am sort of the clinical chief when it comes to prosthetics at UCSF and I really feel that prosthetics is one of these realms that really brings back a lot of light back to the users you know after losing a limb it's really like losing a loved one and to be able to restore that aspect of someone's life give them back to walking giving back to doing physical activity and sports is kind of magical so I started my presentation with a quote from arthur c clarke that any sufficiently advanced technology is indistinguishable from magic I can sum him back to walking back to life shwee is magical if you don't understand that technology it really does look like magic so in talking about prosthetic technology I want to make it kind of clear what type of prosthesis or what kind of plastic stuff we're talking about by definition a prosthetic device is an artificial device to replace or augment a missing or impaired part of the body so these posses can be internal or external internal ones would be like a total knee replacement things that are embedded into the bone on your left you'll see a sample of total knee and on the right a total hip or it could also be something like a dental implant things all embedded into the body internal to the body however today when we talk about external prosthesis the external processes can then also be classified as restorative or functional some restorations cell prosthesis might be an ear replacement or even a nose replacement these are made of silicone paint would be very lifelike and they serve a function in restoring sevens tree improving cosmesis also improving self-esteem for the user as well however they don't restore function getting a prosthetic ear doesn't allow you to hear again from that side or getting a project nose it allow you to you know get this a sense of smell back so we're gonna be talking about external functional prosthesis and the most part that's gonna look like a prosthetic leg or a prosthetic arm as we look at pathetic devices it is pertinent to include orthotic devices the two fields are very intertwined and so I just want to make that clarification I think for our PD students you guys are pretty clear the difference between the two however a lot of people don't know the difference when it comes to a orthoses it's going to be a orthopedic device meant to support an existing limb whereas of course the prosthesis is gonna be there to replace a missing limb we do get some patients that come in as wear clot accusers and describe their devices being their prosthesis or their prosthetic device so just want to make that clear okay so as we talked about the technology we want to first sort of break down a prosthesis what makes up with prosthesis what's the anatomy the first section is gonna be the socket this is essentially our human interface this will be how the devices connect the user how they can control the device it's important for these sections to be very well fitting very intimate to the body it improves comfort improves control and improves patient satisfaction this is sort of analogous to maybe you know a glove for a hand or a shoe for a foot if the shoes three ties is too big makes it very difficult to walk or even to run conversely if it's too tight you got great control but it's not comfortable to wear for more than an hour so the next section other processes may have a joint replacement this could be an elbow like on the left or maybe a knee joint on the right and those will allow to mimic the human body return back range of motion being able to bend at the knee to sit down I've been elbow pick up an item bring your hand to your face to feed yourself and then the last part will be a tunnel device this could be a hand that does the grasping for objects or it could be a foot that interfaces the ground provides that stable platform for standing and progression when walking forward you may end up having additional joints in the hand that could be a wrist unit allowing for rotation with pronation and supination there also might be a wrist flexion unit to allow for flexion extension of the wrist conversely with the leg you might have a torsion unit between the foot in the knee allowing for twisting between the two sections or even an ankle joint that allows for plantar flexion which is toes down or dorsiflexion toes up no offense to the PT students I know you guys know that part already okay so let's talk about prosthetic sockets since it is kind of one of the most important aspects of a prosthesis the historical perspective old sockets were made out of wood back in during the Civil War era james hanger made his socket by using barrel staves wills wood and use that it's interface to attach the processes to the residual limb there also were like the ones you see here made from solid blocks of wood or a practitioner or technician will actually carve out the blocks of wood creating a hollow space to insert the residual limb this was a long painstaking process not very accurate they would use measurements of the limb carve out some of the wood patient trigon if was comfortable great if not carve out more wood it wasn't a lot of scientific thought used to make these devices luckily nowadays we can do things a little bit better and so we actually take a mold of patients residual limb among the conventional ways is to use plaster and that plaster is essentially just hand wrapped around the residual limb and and mold it in the plaster can be massaged it can be compressed this allows kind of really good direct patient feedback while the practitioner is casting we can squeeze a limb the pressure an area that we want to load the limb patient and respond back yes that's comfortable or no that's too tight that's uncomfortable that's painful and so once the plaster set essentially yields a negative mold of the patient's limb that negative mold can then be filled with liquid plaster the negative won't be stripped off then we're left with a positive mold or essentially get a statue of their limb that mold as you see the bottom left can be carved and shaped based upon what forces we're going to apply till them during standing the mold can also be modified by adding more plaster and believing certain areas certain ears you might want to believe bony promises like fibular head disel end of a tibia that has been cut or maybe in here that has an aroma or a nerve bundle that's really sensitive for the patient once all that's completed the next stage of we move into fabrication that plaster model has been put into a fabrication jig where hot plastic is essentially draped over the model and vacuum is applied vacuum sucks the air out molding the plastic directly to the model reflecting all those shapes and contours that the practitioners built into makes for a exact fit the plaster is it once the plastic is cooled the plaster is removed and you're left with a test socket which is essentially back to a negative model clear plastic so we can make a visual assessments once a patient puts the loom into the socket we can see areas that are gapping areas that are of high pressure you might see some blanching of the skin you might see a lot of compression of the tissue and being plastic we're able to heat mold it and reshape that we can make it tighter or make it looser I think increase the patient's comfort the plastic test socket is also durable enough for us to test with the patient standing and walking and this really gives us the ability to confirm that we've done a good job fitting the device make additional adjustments and the patient can try this out for an hour a day it's possible to even send patient home for a week on a test socket and really get long-term use on it and to let us know it's ready to be finalized this process can be repeated multiple times you could reap or classroom make more modifications and make a new check socket at some point you should be done with and hopefully yielding and comfortable device and then moving to final fabrication the classroom model is inlaid up with carbon fiber and other fabric materials those materials are embedded with acrylic and epoxy resins that will link here underneath vacuum so again bringing that shape to the mess the plasma model your final device won't be clear but it will be rigid durable and lightweight we took this from the aerospace industry with all their cool materials and everything ok so let's talk about the digital world that process is very manual requires hand skills and years of learning nowadays you have computers and so someone smart decided to use the 3d world and and do some digital scanning here we have a patient's residual limb and a laser or light scanner being used to get a digital capture of the the limb the beautiful thing about this is the laser scanner has accuracy of about half a millimeter so I can really capture all the shapes all the contours give precise measurements can be done in about five minutes and one of the great things is the reproducibility you don't have to have twenty years in the field to take a great casts or great mold of a patient you can fire the computer and with about 15 minutes of instruction be able to take a scan just as good as somebody who's got 20 years into the field one of the downsides however is because you're not applying any compression or squeezing the limb you don't get that paid direct patient feedback once it's been scanned in a digital CAD file is created there's software out there that will then allow you to do essentially what we do in plaster you can reduce areas you can build up areas based upon how you want that side of 51 to be tighter or to be looser or if you want a global change you can put in parameters to shrink the socket by two percent three percent or fifteen point eight five percent accurately whereas if you do it by hand placer would be very difficult to do once you have digital model there are two routes that you can use for fabrication the first one would be a phone carving where that digital files put a machine that has a robotic arm with a cutting tip to the end of it that cutting device will basically take a block of foam cut all the way around it to yield essentially what would be similar to the plaster model except instead of being made of plaster it's made of foam and you didn't spend half an hour making it the Carver cut it out in about two minutes this foam model can then be taken back to the vacuum forming station and you can make it to socket the same way you did with the plaster nice things about the foam you can also make additional changes like carving through using the same hand tools as you did with plaster or you can add placer and create more release in the in the device the other method of fabricated from digital file would be 3d printing of course this has been really popular in the media lately where the printers will basically use additive manufacturing in and print out the socket not using a foam block the plaster not having a positive model or any waste in that sense they are durable enough to be used for test socket fittings at this point they're not quite durable enough to be used for definitively think about how to fight and match the strength and durability of a carbon fiber to this point okay so now that we know how sockets are made let's talk about how we end up designing the socket we're gonna start with the trans tibial sockets trans tibial just to be clear would be a below the knee style socket so trans being transacted through the tibia which all of our PT students know is gonna be essentially our shin bone so it's gonna be able to lower the knee socket the most conventional style of below the knee socket is gonna be a we'll call it PT B or a patellar tendon bearing socket this socket design has very specific loading areas one being the patellar tendon that's the big 10 and just below your kneecap the counter force and the popliteal keeping it tight and keeping a tight ap debate essentially push the limb forward on top patellar tendon to bear the weight and then your medial tibial flair as well too so that's going to be the inside aspect of your tibia as it curves upwards all those areas are sort of areas of high tolerance for pressure conversely you also have areas of high sensitivity figure head again distal end of the tibia all areas that patients can't tolerate taking weight when looking at a PT B socket you'll notice a lot of very specific contours here in the socket you'll notice there's a kind of deep groove patellar groove for that tendon design and sort of dig into the tendon which is not innervated so it's fairly tolerant of pressure to take a lot of weight here and in a tight posterior wall and as the compressive tissue to maintain contact to that patellar groove then there's usually a large reverse flare curvature here to cradle the tissue that is essentially sort of pooching out the top of the socket so progressing on from the patellar tendon bearing socket was the total surface buried socket and this type of socket really came about because of materials that came out silicon other types of gel at the TPE that case was essentially roll on a gel wire into other limb this provided some cushioning as well as uniform there their limb for global changes so as the name suggests the weight bearings now have taken across the entire limb not just in key specific areas this is great because then those two or three key areas don't have a high pressure from weight bearing now all that weight isn't distributed evenly across the limb thereby decreasing the pressure at any specific point you notice in the socket here it's a lot more uniform there aren't these big contours or curvatures digging into the limb or reversely out away from the limb because again we're not loading you know two or three specific spots were really kind of trying to load the entire limb the style of socket really relies on hydrostatic pressure and compression of the whole limb to hold up the patient and make them comfortable and to provide the control so from the total service brain socket came elevated vacuum sockets the diagram here illustrates the method of how fluid will flow out of the limb as the patients walking doing activity throughout the day so we actually move other limb reducing the volume of the limb and having them the patient's limb drop down to the bottom socket then increasing the pressure at the very bottom generally very painful you by applying vacuum between the surface of the liner and the wall inner wall of the socket we create essentially a fluid balance fluid is escaping but then also being pulled back in via the vacuum this allows for a more uniform and consistent volume of limb and the pressure around the limb stays consistent even about the day the vacuum pumps can come in a couple different forms on the left here we have a mechanical pump this pump is operated essentially by the patient's weight every step they take that Pistons compressing its point air out of the socket evacuate similar to a bike pump and so air going in airs coming out on the right we have a electronic pump this pump is battery-operated and the user will turn the pump on when they dawn our leg and this will evacuate the air to a specified psi that's usually based and set via the practitioner once it hits that specific level of pressure the pump turns off you just can walk around do whatever they want to if they end up having a leak or they sit down for a while and air enters into the socket decreasing their hold in there the contact the public automatic turn back on hit that level of vacuum and then shut back off so the user doesn't really need to do much in way of paying attention to their their negative pressure when this system came about it was very useful for diabetic populations people who had a lot of ulcers that would develop on her limb the elevated vacuum system really did a good job in promoting healing of ulcers because it had that fluid balance and kept a lot of fluids moving in and out of the limb all right and then we progress into adjustable sockets up till now everything's been a solid socket it has been static original once it's done and made final not a whole lot of adjusting can can occur so recently there's been adjusted SEC have been have come about the adjustability can come by via specific panels the long seat here has three panels the one in the popliteal region the medial tibial flare and probably a pre tebow region and these are generally areas are able take high pressure so the user can adjust or fit throughout the day if they feel a little bit loose they can crank it up get a little more compression feel more comfortable if you can do something like play basketball kind of hat TV they can get more control of that or if they end up sitting down watching a movie being a lecture it feels too tight they can pop it loose let the tissue and all the food relax dejectedly can also come more globally either by the soccer in the middle where it tends to have more of the front to back or an AP closure to make to account for the jessica's aspect or the socket on the left where it's more circumferential as a user tightens it it closes in the circumference of the socket increasing the pressure and the control okay so we're gonna move into the transdermal sockets and see how they've progressed over time the most conventional is the quad socket sorry we talked about trance femoral now we're talking cutting out the femur which essentially would be an above-the-knee amputee the quad socket it's aptly named because it looks like a square it's got four sides we can't the picture down bottom right this would be a cross view looking down into the socket with the dark area being the femur and the surrounding muscles and tissues and then the wall of the socket all the way around this diagram gives you a good representation of anterior front of the socket posterior the back in the socket lateral which would be the outside or away from the midline of the body and then the medial side which is towards the midline of that inner thigh side of the thigh and so with that orientation we can tell if this is a socket for a right transferrable user the design of the socket is to bring the weight bearing pressure up to ischium and looking at this diagram here we notice the transected femur doesn't have any areas to take loading stress once the femurs cut there's no weight bearing surfaces so bearing weight at there very disciplined of a cut femur it's very uncomfortable very painful so we have to move more proximal up to the that pelvis so we'll see here the ischial tuberosity is now resting on a shelf for vertical load and we very on the left is picture of a quad socket and the person is point at where the issue actually in the socket in order to maintain that issue a placement in the socket it does require to have a tight ap or anterior dimension otherwise the issue will sort of fall inside the socket and cause the bottom of femur hit the bottom of the socket and be very uncomfortable for the others you that don't know the issue here is essentially our butt bone that probably gets really uncomfortable eats into the hard chair or ride a bike for a long time so not an intuitive spot to take pressure but again without any weight bearing surfaces on a cut femur that's the next available space for vertical load one of the problems with this socket design is there is an instability inherent in the socket design that ischium that takes a lot of the weight bearing can essentially slide back and forth on that so that shelf many of you students might know that it's Trendelenburg gait so then the next development of the transform of sockets is the issue of attainment socket again here on the Left we have the same picture of the quad socket with the ischium suchlike sitting on top itself able to move left to right this diagram up here is the issue of attainment socket where the issue actually sits inside the socket so essentially there's a vertical wall from that shelf to contain the issue and then the lateral wall goes up over the troch really locks in the femur and the pelvis and what we call a skeletal ml dimension and that really provides a lot of public stability during singledom support here's a picture of kind of a finished socket you can notice the high medial wall so the ischium will sit on the shelf here and then the medial wall will contain it so if you can imagine your butt bone sitting on that hard bike seat now imagine a wall and inside of that containing it keep with them sliding around it can be a very invasive socket and up till now just like the chance to be osaka designs we've been looking at solid sockets solid walls again rely on the hydrostatic pressure a little diagram here so the blue line is the would represent the socket the inner grey circle is the bone and the space in between will be fluid soft tissue muscle and the compression essentially will provide force into the limb and limb and the hydrostatic pressure would pushed outwards to the socket the downside of this design is if the patient's limb reduces in volume essentially the socket becomes very loose so one of the developments in trance ephemeral sockets as the vector design socket Matthews actually been a big part of this and developing it at UCSF the vector stands for vector enhanced compression and tissue relief in the diagram here the blue line again is our socket so you'll notice it's driven much closer to the femur and in order to do so the muscle soft tissue fluid need to escape somewhere else so the socket itself is actually open and these tissue release here would coincide with how the white or the beige areas in the picture here so you have tissue coming out in order to let the socket drive in nice and tight and stabilize the femur by stabilizing the femur in this way we don't rely on the containment of the issue so this shelf can be just at the ischial level and really keep all the trim lines much lower much more comfort for the user so the future of the sockets though instead of having to deal with hard sockets high trim lines invasive trim lines someone thought about hey let's eliminate the socket how do we do that we don't have a socket the next thing is to then go and implant into the bone so this is being done here at UCSF the illustration here shows the bone and there is a fixture screw that gets surgically implanted into the femur that fixture screw if under microscope actually shows a lot of force openings so the bone actually grow into the fixture screw and really truly integrated to be human body the next piece would be in a button that interfaces to the facial screw and is transdermal so it actually crosses the skin and the other end of the above and screw would interface to the prosthesis this allows the user to then take their weight bearing instead of on addition actually through their skeleton back to how our bodies are normally and naturally designed to do so one of unique things about the system that we use here is the axe or component this piece would thread on to the abutment and this is something that you can do this would be the section where they would leisure would take on and off at nighttime when they go to bed or get up in the morning to put it on and a hand tool they'll it works just like a hand drill and the Chuck you loosen it and the jaws open and close and so usually we'll be able to put it on themselves take it off every night and the really unique thing about the axe or is that essentially works as a torsion break release mechanism the patient does some kind of high activity that was a lot of stress on the processes and their limb maybe potentially Falls instead of all that torque and that force going into their limb potentially breaking their femur or loosening the fixture screw the axe were actually releases itself taking off all the stress and dissipating it away so here we have a video of basically donning the axe or so you'll notice no socket coming up the thigh no compression no skin discomfort weight bearing goes directly through the femur and back to his pelvis just away he's used to stand before an amputation okay so now we're gonna go into prosthetic knees okay now that you know everything you need to know about sockets we're gonna talk about prosthetic knees so of course a prosthetic knee joint is required only for any amputation above the knee right so that's gonna be a knee disarticulation amputation transfer Merle through the femur anything transecting the femur the hip disarticulation amputation how am I pass out to me and so on and so forth so just to understand a little bit of historical perspective of Dee's this is kind of a fun little bit of history so dating as far back as the 1500s we know of Ambrose Parr a who's who was the official barber and surgeon of the kings of France in the 1600s interesting combination of titles and he introduced modern amputation techniques and procedures for the medical community and in fact design prosthesis which is it's was rare then it's unheard of now that the amputating surgeon would also provide the prosthesis so that was kind of unique but what he's really known for is the creation of these custom prosthesis that had a locking mechanism or a locking me in the stance phase of gait to provide stability for the patient interestingly enough we employ some of these same designs still yet today so prosthetic knees are really stratified into really four main categories mechanical knees pneumatic knees hydraulic knees and microprocessor knees we won't talk about pneumatic knees because we don't use them as commonly anymore and it'll also talk about little bit more of an advanced technology known as powered knees and we'll go into that in a bit so there have been several mechanical needs that have come to market over the past century all varying of varying unique designs these are typically devices that are used for lower level amputees who are walking at a fixed cadence they're relatively light and inexpensive but they all have three basic features stance phase stability so if you wait there on the knee it has some sort of a braking mechanism to prevent the knee from falling or breaking and the patient from following in the stance phase of gait they all have or most of them have a friction adjustment that acts as a decelerator of the knee through the swing phase of gait another way to say that is the friction adjustment acts as your quadricep and your hamstring complex through swing preventing excessive knee flexion and extension through swing and many of them have what is referred to as an extension assist to help advance the limb from the end of stance and it through the the swing phase of gait the problem with the mechanical knee again it's it's they're they're really designed for lower level amputees especially nowadays is that the friction adjustment used to decelerate the knee through swing to prevent excessive heel rise a reflection and an or excessive terminal impact or an abrupt extension is really insufficient the this friction adjustment is insufficient and so the advent of or the incorporation of hydraulic fluid into the knee unit was seen some time ago and these are early examples of early hydraulic knee units that helped dampen the the the swing the swing or the pendulum type of action of the of the lower extremity through swing the wavefunctions is actually quite simple and a common usage you see is a hydraulic cylinder on a door so if you push lightly on that door few valves will open not a lot of hydraulic fluid or rush into the cylinder heads and it'll be easy to open that door if you push hard conversely more valves will open more fluid will rush into this to the cylinder head gonna be very hard to open so that prevents the door from swinging and and bumping into somebody or something along those lines it works very similarly a hydraulic knee unit you walk fast and quickly aggressively more valves open more more fluid rushes in and it's stiff to prevent the success of knee motion conversely if you walk slow it's it's easier to bend but it won't be easy for the user to bend and excuse me without a lot of excessive hydraulic resistance so the problem with those early knee units was that although they addressed the swing phase issues that amputees were experiencing they didn't address the stance phase issues and what I mean by that is there was no stance resistant so patients were falling falling so the advent of the malc knee unit really addressed much of that in that allowed for stance phase hydraulic resistance as well so in theory this knee did it all it was a great knee it was used for many years still used in many cases the problem is we experienced many environmental barriers throughout the day we could stumble by catching our toe on a root or an uneven sidewalk there are a variety of environmental circumstances where in which a standard mechanical knee isn't always the best option it is something that essentially has a brain and can think for the amputee to prevent them from falling so in the early to mid 90s there were a number of microprocessor knee units or MP Ches as we call them that were introduced to the marketplace the most notable knee picture in the upper right is the C leg a product designed by a German prosthetic manufacturer by the name of Otto Bock and it came to be the most reliable and and is considered that was considered the best functioning microprocessor knee unit of the time and I think in many ways still is today and so the concept is this there's a central processing unit at the top of the knee that reads where the patient is engaged how do they how does that happen so the pylon which is pictured to the right of the knee actually has strain gauges built into it so that strain gauges reads toe and heel loads as ground reaction forces that data is then transmitted to the CPU it sits at the top of the knee and it is monitoring the patient's gait at 50 times per second and with that information it's able to assess that the patient is is or excuse me the knee is get is giving the appropriate amount of hydraulic resistance necessary for the phase of gave the patient is in and thus can assess whether or not the patient is stumbling whether or not they want to descend a ramp or stairs and will give them the exact appropriate amount of hydraulic resistance for the phase of gait they're in or the situation that they may find themselves in so the mix the next most logical step of prosthetic innovation beyond the C leg which is essentially a knee that allows for eccentric contraction or lengthening of the quadricep complex descending a ramp or descending a stair is a concentric lengthening contraction of that muscle how do you go up the upstairs how do you go up a ramp you need a concentric contraction or a powered knee so that's the next innovation we're biomechanical engineers have focused a lot of their energy so this is a power neither allows for both concentric and eccentric contraction this simulates the true function of a quadricep muscle group the problem is that many researchers didn't realize the power requirement for such a unit and the and the power of assume a the battery pack size and weight that was required to make something like this happen and so these units ended up being very large and very heavy and still today are seen as being somewhat investigational by clinicians researchers and payers alike so this concept of a synergistic relationship between foot and knee excuse me India between the ankle which is where all the powers is derived in a normal human lower extremity and the knee it really remains the sort of ultimate or preeminent goal of creating the very best transfer all prosthesis so this combat this combination of net power derived from both ankle and knee is very interesting to researchers and there's a lot of work surrounding this area in many institutions across the country so the idea is a joint project right now between van der Pell van der Bilt's Centre for intelligent mechatronics and the rehab Institute of Chicago's Bionic Medicine Center for Bionic medicine where they've created this bionic knee this was featured on a I think a CNN or a 60 minute segment where this gentleman walked up a hundred and three flights of a Chicago skyscraper just to demonstrate how amazing this a me ankle net of power generation can be something that many of us with to sound limbs couldn't even do so it's a pretty impressive feat and that will move to prosthetic feet awesome so all that great work that need us needs to integrate somewhere to the ground so that it's gonna go to the foot and some of the one the first feet that was made out there was by dr. Douglas supply which he made it from a polished ivory ball and a lot of rubber tendons that allowed a lot a lot of ankle inversion e-version pioneer in dorsiflexion which we don't use anymore today but instead when the conventional feet we do use it happens to be made of wood and foam so this is called a sach foot it stands for solid ankle cushion heel so there isn't any plantar flexion or dorsiflexion in the foot but instead the cushion heel down the bottom would serve as a pseudo plantar flexion moment during in as a contact and loading response the wooden keel provides the stiffness and stability for mid stance and then you'll notice that the would keel ends just by the met heads and a foam continues to allow for essentially dorsiflexion of toes are rolling forward into terminal stance very basic but still very stable when we use a lot still nowadays for a brand new epic tees who don't have the ability to bounce themselves over maybe a dynamic foot or a foot that has power so we great starting point from there as materials improved and became readily available we moved into energy storage and returned feet so and the bottom picture still a similar design to the sach foot we'll still have some foam or maybe a polyurethane bumper in the heel to provide shock absorption and that pseudo plantar flexion but now the keel of the foot is made of Delrin various plastics even maybe the carbon fiber so as a patient progresses forward rolls over the keel essentially like a diving board it stores that energy either deflects and then when they come to that terminal stance and pre swing that energy sort of rebounded back and some of the energies give it back to the user decreasing their needs used energies are walking they've also developed an articulated feet so bringing in actual ankle joint usually across a single axis pivoting this allows for true plantar flexion and true dorsiflexion of the foot so going up and down hills made it a lot easier for amputees but the articulation can't just be a free swinging hinge just like the mechanical knees needs to have some sort of braking force or some sort of resistance so the patient can actually balance on that earlier versions would use you think bumpers or rubber bumpers in the posterior in the front to slow it down this particular foot here uses hydraulic cylinders so we can adjust how quickly that a deflection occurs or how quickly the dorsiflexion occurs as a patient moves into terminal stance then we get into some more exciting feet which I think a lot of people are kind of familiar with that's a dynamic response feet made fully of carbon fiber these feet take a page from the energy storage of a turn foot and take it farther now we see or in the keel the keel is continuous from the forefoot all the way up the shank of the foot at some point the socket would be attached up here so now you have much longer lever arm to deflect to store energy and then return back to the user everyone I think now nowadays is pretty familiar with the prosthetic running feet especially after Oscar ran in the Olympics which essentially you'll notice a design is slightly different a larger curvature for more interview storage or return but also no heel mechanics are running don't really have you heel striking but in the prosthetic walking feet there still is a heel put in there so patients can balance still have a heel toe gait but still giving all the energy and return back and these are the most common feet for active users out there anybody who walks kind of unassisted out in the community so they're pretty common even though you don't see them you know walking with a blade a lot of them can walk very well and even jog and somebody's non-running dynamic for spots feet and so the feet have really started to progress in to follow the knees and now have microprocessor controls so that articulated saw earlier with the hydraulic cylinder it now gets a computer to control it as opposed to just a passive cylinder of computer similar to the knee is reading strain gauges some of them have accelerometers in them so it looks kind of know where the foot is in space they'll have we be able to reach or the patient's speed and then adjust that I draw a cylinder or some kind of torture unit to change the rate of movement in plantar flexion or endorsed reflection some have small motors in them which will dorsiflex the foot help with going uphill or just flexing so I can clear stairs when climbing up and down the stairs however you're still on the passive side of things there isn't any active plantar flexion or propulsion when when walking but that wouldn't go into the next realm of Bionic feet these are now out in the market they are not highly use mostly because from a payer standpoint but our friend Hugh Herr doctor Heuer of MIT has designed the biome I think it's maybe got a new name now but it's the first prosthetic foot that actually has powered propulsion powered plant selection in it there are videos of bilateral below-knee amputees running uphill with these feet which is not something that would quite a lot more energy to do in the past one of the downsides of the foot similar to the powered knee is the amount of energy it takes in order to power the torque and the motor so you notice the battery here is very similar to like a drill battery require that much power and it only lasts about four or five hours of the day so you usually have to change out to three batteries to get through the day weight of the Bionic foot almost like ten pounds which ends up being quite a bit at the end of a prosthesis but as technology is better it's already getting smaller getting lighter and hopefully you know all the insurance companies will start paying from the more so we fit more than one on patients all right upper extremity prosthetics okay so on to the world of upper extremity prosthetics so another fun historical slide this gentleman in the upper right hand was a German Imperial Knight and a mercenary actually who lost his his one of his arms and in fact in a battle and what he designed for himself was one of the first recorded multi articulating functional upper extremity prosthesis and interestingly enough we did not see multi articulating prosthetic hands in the marketplace until it made me about seven or eight years ago so it took awhile for things to come full circle another interesting historical slide so so following up World War two the Surgeon General at the time realized that this the the current state of prosthetic innovation at a time especially in the upper extremity arena was lacking and they launched an initiative to improve care and functional outcomes for these patients so the u.s. brokered a deal with several small private developing developers to compete essentially to create the next latest and greatest upper extremity prosthesis and sort of the net result of all of that is what we now know is external power prosthetics or more commonly known as myoelectric prosthetics and and so in the bottom right is an example of the schematic of one of the first iterations of that and we use very much you'll see a couple of slides here in a second we use very much the same set up with two surface electrodes place in antagonistic positions with a battery the hand they use uses pneumatic actuators we don't use that anymore but it's just amazing that in many ways we have in advanced as quickly as we would like to so upper extremity again new just to Stratus stratify the different categories it's broken out between passive functional or cosmetic prosthetics body powered or conventional prosthetics also known as cable driven devices and then external powered devices at the external powers of battery essentially a motor is what drives it but they could be powered either through mile electrics meaning a sensor placed a surface electrode on the skin or maybe a switch or a transducer those are the three main types and we'll talk about other types of prosthetics moving forward so passive functional devices are just that in the name they're passive in nature the the hands don't articulate in any in any real way other than perhaps passively positioning them with a Concha lateral hand typically most of these hands are static in a position most patients seek out these devices because they are quite cosmetic and appealing to the eye but they have a function as well these hands can be used to perhaps stabilize a piece of paper when writing it can be used to stabilize a large object for by manual dexterity when when picking up an object so they can be quite functional as well I also find that just adding the prosthesis creates symmetry in the spine of the paraspinal muscles and of the trunk musculature as well so there's a lot of reasons why someone would use a cosmetic prosthesis so we don't call them cosmetic prosthesis for that reason we call them pass a functional so body powered devices are really the mainstay of prosthetics you know a lot of times when people think of an upper extremity prosthesis they think of the hook a cable driven device and it rightfully said they've been used for a number of years and they're still very very functional and we use them today so the concept is simple you're you're extrapolating gross body motion to elicit a function of your terminal device or your hand is the terminal device could be a hook or hand the terminal device is a broad term that we use so in this case we use shoulder protraction glenohumeral fraction of flexion to provide excursion cable which is attached to a harness that a patient wears and that cable is pulled and then and thus that elicits the the terminal device activation or the opening of the hook as you relax after after a protracted you retract the terminal device will then close the amount of pinch force is really depend upon dependent upon the number of bands or springs incorporated in that terminal device so though we are no longer using a pneumatically driven hands like I was saying earlier some of the same basic principles of external power myoelectric devices still exist today basically how it works is the central nervous system elicits an action potential which travels down a motor neuron which then creates flexion or contraction of a muscle in the residual segment of course that contraction has electrical activity about it which the surface electrode placed on the skin picks up rectifies and actually converts to a voltage which is then sent to a circuit in the hand or a central process of the CPU in the hand to elicit a particular function based upon however we decide to so you know believe it or not this is a it sounds complicated but it is a continuous process from from thought to to function so my electrics again use EMG signals to control these devices my electric devices electromyographic signals and this is a basic setup of a most mile electric devices so either you have you have whichever hand or terminal device you want to use be it a hand or be it a work hook a moving right is a actually a motorized wrist so for example if you have a transradial higher level transradial level amputation you no longer have as much supination and pronation as you normally would have had so you can use a motorized unit to to simulate that the the two devices standing off of the motor are actually electrodes or the two little leads those are placed on antagonistic muscle groups opposite contractions so again in the instance or the example of a trans radio level amputation you have forearm flexors and for our extensors the forearm flexors typically would be used to close the hand and the form extensors would be used to open the hand and then in the middle there there's a there's a battery that's pictured those are the basic components of a mild electric system so greater exploration and hand function has led to the development of multi articulating individual individually powered digits this concept obviously wasn't revolutionary as we had discussed earlier it was obvious that we needed more dexterity than the basic dynamic tripod of most of the early hands the problem is the hands were doing really amazing things and had all these this great individual digit manipulation but we couldn't control it and in many ways we still can't today which brings us to dr. Kagan who developed a targeted muscle reinnervation so in our higher level amputees perhaps in a shoulder disarticulation amputation or an inter scapular thoracic level amputation where the entire shoulder girdle is missing trying to utilize those really fancy hands can be quite difficult with crude motions gross body motions with a cable or even just using an a pectoralis muscle which is not very intuitive to fire your PEC to elicit an EMG signal to bend your elbow and to bend your hand patients want to think about bending their elbow and then the elbow bends well how do you do that so TMR is very complex and yet very simple so I'll explain it so in the case of a shoulder disarticulation or inter scapula thoracic amputation the nerves that serve biceps which is no longer there right and this would be the sort of the host muscle or the targeted muscle is no longer there the entire extremity is gone but the muscle that serves it in this case musculocutaneous which would serve biceps to flex the elbow is there it's safely nested in your brachial plexus so so you can reroute or redirect or reinnervation tree innervated to an existing muscle group so you could redirect it to pectoralis major for example and when you think about bending your elbow now your pectoralis fires we can pull off EMG signals from that and reroute that to a motorized elbow so now you're thinking about bending your elbow and you really are it's pretty cool stuff so it's interesting how history tends to repeat itself similar to the apparent deficit after World War two at the time the state of upper extremity technology following our most recent military campaign in the Middle East there had been a similar sentiment and so as a result there have been millions of DARPA dollars invested into oftentimes private sector projects the grant criteria for these for these DARPA grants has very specific inclusionary criteria and the most notable of which being creating a device with multiple degrees of freedom of motion current prosthetic devices have very limited degrees of freedom of motion flexion at the elbow may be wrist rotation and the transverse plane and may be hand opening and closing and as we all know the normal human upper extremity has many more degrees of freedom of motion than that and to conclude as a final control mechanism was I think you can see that the the technology is there it's how do we control it and that's where a lot of the science is being focused on right now is there are projects where we can essentially oh that are working towards essentially connecting the prosthesis directly to the central nervous system to the brain here at UCSF for example we have the C NEP the Center for neural engineering and prosthesis which is a UC Berkeley UCSF a joint project to create prosthetic extremities at this point for spinal cord injury patients but I think the long-term intent is to also incorporate that into the prosthetic community other groups are working hard at work at implanting small electrodes in the periphery to allow for very fine point dexterity of a prosthetic hand because they're putting isolated electrodes in the muscle groups that would function the hand at a very fine level and with that I think we have concluded our talk so thank you very much for listening [Applause] [Music] you

Channel: University of California Television (UCTV)

Views: 3,135

Rating: 4.7894735 out of 5

Keywords: Prosthetics, joint replacement, socket technology

Id: vLc3fl1xuVc

Length: 58min 28sec (3508 seconds)

Published: Tue Apr 17 2018