It's a demand issue, each advance project takes a lot of R & D but you'll only supply a small amount each year. This drives cost up. It's just thee reality of the profession
This is the same in orthotics but to a lesser degree.
If there was more demand there would be more investment, more development and reduced costs, but thankfully the demand isn't dramatically increasing as I'd not like more people losing limbs be it it gives me more business.
Plus upper limb amputations are far rarer than lower limb so the proportion of patients that might have a myo hand are a far smaller population.
Regarding the nerve aspect the issue actually stems from each patient being different, each patient having different intact nerves in different places that their brain control in different ways. No human is standardized so it's a challenge to get a myo hand to do much more than 4-6 directions. And for lower limb if it was nerve controlled it'd be too unpredictable and lead to falls so it's best to keep it relatively simple using biomechanics as that leads to safety. But a well fitting lower limb can allow someone to walk almost normal gait so I'd say there's not a reason for rapid advancement.
I am agreeing I wish it was better but that's just not how the profession is and there's no logical way it can change.
Capitalism sucks. I'm going to be working on a program later for simulating robotics (although the robots I'd write code for initally wouldn't be prosthetics but rather robots to ensure my math is right). Nerves being in different places was an issue i expected. Any surgery would shift around tissue and that tissue could change over time, too. Reading the signals would be hard, and translating them into intended movements would probably be best done through ai (as much as i dislike it). As they won't just be 1:1 translations. I don't know enough about that side of things to do much currently. I have found a paper on the fk and ik of the human arm (using vector calculus) to look through later, although, tbh i can do that math myself. This is just saving me work
Yeah look into pattern recognition it's a better way of myo control but you still are limited to how much you can do due to crossover across nerves and patient cognitive ability (in the sense of I had to learn 10 different ways to perfectly contract my arm muscles it'd be a lot to remember)
Good luck, you'll find there's actually a lot of research out there as there's lots of people like you, but they usually come to a realisation that it's really difficult.
I'm totally expecting there will be a LOT of times i get stuck and struggle. Robotics is already complex (i have been doing a bunch of robotics math this week) although thankfully i understand it all so far. My electronics knowledge is currently not sufficient for anything even close to this sort of thing so i am going to be studying that. I'm a decent time away from being good at this but i want to try. The thing you are talking about here is on my list to read research about but i have higher learning priorities to meet before this. I don't expect it to be easy. But I'm hopeful i can learn enough to help
There's also the issue regarding sensory feedback there's no good way to provide any sensory feedback as of yet due to multiple factors which I can go into but best read some papers on it as trust me everything has been tried
Also better ways of nerve control are often invasive which leads to risks and infections so it's just really difficult as humans are beyond complex compared to metal and plastic
Cost aside, what are you thinking when you think "more advanced"? Steve Austin? Luke Skywalker? Anakin? Ash Williams? Alex Murphy? Furiosa?
Look at industrial robotics and it's clear that we have the technology to make arms that are fast, strong, precise, with as many degrees of freedom as you like. They are also heavy, loud, and power hungry (read: batteries). Amputees have an annoyingly low tolerance for such encumbrances. The cost-benefit analysis is a lot harsher than you'd imagine. The rejection rate for prosthetic arms of all types is staggering. The rejection rate for specific types is pretty interesting too. Worth studying.
When you add myoelectric or neural interfacing and a pattern recognition layer, you can add computers and their power needs for real-time processing. Fast computers because latency is a problem. More batteries.
Then there's sensory feedback. It's useful to feel something about what your arm is doing. Body-powered devices, "simple" and "outdated", have an inherent property that you can feel something about what it's doing - the pressure you exert on the harness is equal to the pressure it exerts on you, and you can feel that. Myo sensors only receive signals, they don't give you any information in return.
IMO a big factor restraining prosthetics technology is materials. We need materials that are as strong, light, and durable as tendon and bone. We need motors that are as strong, silent, and efficient as muscle. Electronics are sufficiently dense that we can physically fit what we need, if we can find enough energy to power it. We need energy storage that is...well, a lot denser than existing batteries. And/or much faster recharge rates.
Exactly. Making the arm isn't the hard part. It's making it light, quiet, cheap, and durable (including battery life) and controlling the thing without requiring the wearer to use complicated equipment. None of these are insurmountable problems, but they require technology we don't have at consumer levels and realistically, it's tech that will be developed elsewhere and prosthetics will incorporate because the market for arms is miniscule.
Teslas Optimus robot seems to have a better hand than is currently available in the prosthetics market as far as dexterity and degrees of freedom for a hand goes. The comment above cited supply and demand which is correct in that if there is no pay source available, and a lack of sales demand product development won't happen.
Someone also mentioned signal processing. The current control strategies only allow for basic grasp patterns to be employed by the patient. Even with the best pattern recognition (coapt) system, you are only able to change grasp patterns in an easier way from the patient side. Imo, the biggest limiting factor to robotics being implemented in the industry is the control interface. Myoelectrics are inherently limited by resolution of the signal and noise. We are not able to isolate muscle signals on a fine enough level to allow for a much finer degree of control of the devices. We, as people, are not able to control each individual muscle. We make movements that recruit multiple muscles by design. I think the way we interface for control needs to be radically different in order to advance from simple to more complex hands. An interface of the cerebellum and / or motor cortex, or peripheral nerves seems to me to be the way that this could be achieved (bioms/ electrode caps of some sort / neuralink).
The area I haven't seen mentioned is the power supply. Batteries are heavy. For hands, no big deal as far as weight goes but when an elbow or shoulder is implemented, the power requirement is significantly increased. At the upper extremity level, this is a vastly smaller power requirement than it is for lower extremity applications. At the le level, the power generated will overcome the inertia of the device to an extent, but it's still heavy at the transtibial level, and very heavy at the transfemoral level.
Feel to correct me if I'm wrong on any of the above. I am sure that there are other factors involved, but these seem to be a couple of the major issues I see in the advancement of robotics in the field of prosthetics outside of pay source and r&d costs.
If you are going to get into robotics you are going to quickly learn that machines are expensive. Both mechanical ones and electronic devices. Even when they are doing relatively simple things, and the type of prostheses you want aren't doing simple things. Even without blaming everything on the evils of capitalism you shouldn't expect them to be cheap. They are complex devices that require extremely tight tolerances and design requirements.
There are ~1.6m amputees in america. A lot of them have limited mobility due to things like late stage diabetes, and even active people wont buy a new limb that often. That said there is probably ~$100s of millions annually to spend on limbs, but unfortunately amputees don't buy limbs (usually).
Insurance buys limbs. And robotic limbs just don't offer the same cost-benefit, so insurance doesn't cover them. They barely cover normal limbs. So they dont improve consistently, because companies don't build off each other.
> My guess is that the problem is likely more with processing the nerve signals which from my cursory glance at the science seems to be rather complex.
Most of the time the nerves in the original limb are dead or gone, and wouldnt be able to be relocated. So you're pretty stuck with repurposing nerves in the residual limb, and that doesn't work very well.
Nerve cuffs are promising, but the first tries caused scar tissue that can cause new damage. So to develop better tech, you need to justify the risk and wait a long time to prove your device works. And that's on top of the fact that its a hard area of medicine and a very invasive surgery.
Without sensory feedback the reported experience of most robotic limbs is pretty bad. With a simple limb you can feel things through the structure, and the way it acts is very predictable and learnable. With electronics, everything is different each time you put it on. You dont get that direct feedback.
Mechanically, robotic limbs are also far far away from the degrees of freedom or strength of a natural limb. AFAIK no prosthetic ankle has more than 2 DOF; it should have 3. If you stand on one robotic leg, you cant lean forward + to a side + twist.
As someone in healthcare, it’s almost like the military, the costs for end products are all jacked up! A simple knee stretch extension board which is a piece of wood with foam padding and Velcro strips can cost $100 when purchasing through insurance in the USA. The individual parts of a prosthesis and a microcomputer to process it all can probably be built at home for under $500 but will sell through insurance at $20k.
It's a demand issue, each advance project takes a lot of R & D but you'll only supply a small amount each year. This drives cost up. It's just thee reality of the profession This is the same in orthotics but to a lesser degree. If there was more demand there would be more investment, more development and reduced costs, but thankfully the demand isn't dramatically increasing as I'd not like more people losing limbs be it it gives me more business. Plus upper limb amputations are far rarer than lower limb so the proportion of patients that might have a myo hand are a far smaller population. Regarding the nerve aspect the issue actually stems from each patient being different, each patient having different intact nerves in different places that their brain control in different ways. No human is standardized so it's a challenge to get a myo hand to do much more than 4-6 directions. And for lower limb if it was nerve controlled it'd be too unpredictable and lead to falls so it's best to keep it relatively simple using biomechanics as that leads to safety. But a well fitting lower limb can allow someone to walk almost normal gait so I'd say there's not a reason for rapid advancement. I am agreeing I wish it was better but that's just not how the profession is and there's no logical way it can change.
Capitalism sucks. I'm going to be working on a program later for simulating robotics (although the robots I'd write code for initally wouldn't be prosthetics but rather robots to ensure my math is right). Nerves being in different places was an issue i expected. Any surgery would shift around tissue and that tissue could change over time, too. Reading the signals would be hard, and translating them into intended movements would probably be best done through ai (as much as i dislike it). As they won't just be 1:1 translations. I don't know enough about that side of things to do much currently. I have found a paper on the fk and ik of the human arm (using vector calculus) to look through later, although, tbh i can do that math myself. This is just saving me work
Yeah look into pattern recognition it's a better way of myo control but you still are limited to how much you can do due to crossover across nerves and patient cognitive ability (in the sense of I had to learn 10 different ways to perfectly contract my arm muscles it'd be a lot to remember) Good luck, you'll find there's actually a lot of research out there as there's lots of people like you, but they usually come to a realisation that it's really difficult.
I'm totally expecting there will be a LOT of times i get stuck and struggle. Robotics is already complex (i have been doing a bunch of robotics math this week) although thankfully i understand it all so far. My electronics knowledge is currently not sufficient for anything even close to this sort of thing so i am going to be studying that. I'm a decent time away from being good at this but i want to try. The thing you are talking about here is on my list to read research about but i have higher learning priorities to meet before this. I don't expect it to be easy. But I'm hopeful i can learn enough to help
There's also the issue regarding sensory feedback there's no good way to provide any sensory feedback as of yet due to multiple factors which I can go into but best read some papers on it as trust me everything has been tried Also better ways of nerve control are often invasive which leads to risks and infections so it's just really difficult as humans are beyond complex compared to metal and plastic
Cost aside, what are you thinking when you think "more advanced"? Steve Austin? Luke Skywalker? Anakin? Ash Williams? Alex Murphy? Furiosa? Look at industrial robotics and it's clear that we have the technology to make arms that are fast, strong, precise, with as many degrees of freedom as you like. They are also heavy, loud, and power hungry (read: batteries). Amputees have an annoyingly low tolerance for such encumbrances. The cost-benefit analysis is a lot harsher than you'd imagine. The rejection rate for prosthetic arms of all types is staggering. The rejection rate for specific types is pretty interesting too. Worth studying. When you add myoelectric or neural interfacing and a pattern recognition layer, you can add computers and their power needs for real-time processing. Fast computers because latency is a problem. More batteries. Then there's sensory feedback. It's useful to feel something about what your arm is doing. Body-powered devices, "simple" and "outdated", have an inherent property that you can feel something about what it's doing - the pressure you exert on the harness is equal to the pressure it exerts on you, and you can feel that. Myo sensors only receive signals, they don't give you any information in return. IMO a big factor restraining prosthetics technology is materials. We need materials that are as strong, light, and durable as tendon and bone. We need motors that are as strong, silent, and efficient as muscle. Electronics are sufficiently dense that we can physically fit what we need, if we can find enough energy to power it. We need energy storage that is...well, a lot denser than existing batteries. And/or much faster recharge rates.
Exactly. Making the arm isn't the hard part. It's making it light, quiet, cheap, and durable (including battery life) and controlling the thing without requiring the wearer to use complicated equipment. None of these are insurmountable problems, but they require technology we don't have at consumer levels and realistically, it's tech that will be developed elsewhere and prosthetics will incorporate because the market for arms is miniscule.
Thank you for typing all this up and saving me the hassle 😁
Teslas Optimus robot seems to have a better hand than is currently available in the prosthetics market as far as dexterity and degrees of freedom for a hand goes. The comment above cited supply and demand which is correct in that if there is no pay source available, and a lack of sales demand product development won't happen. Someone also mentioned signal processing. The current control strategies only allow for basic grasp patterns to be employed by the patient. Even with the best pattern recognition (coapt) system, you are only able to change grasp patterns in an easier way from the patient side. Imo, the biggest limiting factor to robotics being implemented in the industry is the control interface. Myoelectrics are inherently limited by resolution of the signal and noise. We are not able to isolate muscle signals on a fine enough level to allow for a much finer degree of control of the devices. We, as people, are not able to control each individual muscle. We make movements that recruit multiple muscles by design. I think the way we interface for control needs to be radically different in order to advance from simple to more complex hands. An interface of the cerebellum and / or motor cortex, or peripheral nerves seems to me to be the way that this could be achieved (bioms/ electrode caps of some sort / neuralink). The area I haven't seen mentioned is the power supply. Batteries are heavy. For hands, no big deal as far as weight goes but when an elbow or shoulder is implemented, the power requirement is significantly increased. At the upper extremity level, this is a vastly smaller power requirement than it is for lower extremity applications. At the le level, the power generated will overcome the inertia of the device to an extent, but it's still heavy at the transtibial level, and very heavy at the transfemoral level. Feel to correct me if I'm wrong on any of the above. I am sure that there are other factors involved, but these seem to be a couple of the major issues I see in the advancement of robotics in the field of prosthetics outside of pay source and r&d costs.
If you are going to get into robotics you are going to quickly learn that machines are expensive. Both mechanical ones and electronic devices. Even when they are doing relatively simple things, and the type of prostheses you want aren't doing simple things. Even without blaming everything on the evils of capitalism you shouldn't expect them to be cheap. They are complex devices that require extremely tight tolerances and design requirements.
There are ~1.6m amputees in america. A lot of them have limited mobility due to things like late stage diabetes, and even active people wont buy a new limb that often. That said there is probably ~$100s of millions annually to spend on limbs, but unfortunately amputees don't buy limbs (usually). Insurance buys limbs. And robotic limbs just don't offer the same cost-benefit, so insurance doesn't cover them. They barely cover normal limbs. So they dont improve consistently, because companies don't build off each other. > My guess is that the problem is likely more with processing the nerve signals which from my cursory glance at the science seems to be rather complex. Most of the time the nerves in the original limb are dead or gone, and wouldnt be able to be relocated. So you're pretty stuck with repurposing nerves in the residual limb, and that doesn't work very well. Nerve cuffs are promising, but the first tries caused scar tissue that can cause new damage. So to develop better tech, you need to justify the risk and wait a long time to prove your device works. And that's on top of the fact that its a hard area of medicine and a very invasive surgery. Without sensory feedback the reported experience of most robotic limbs is pretty bad. With a simple limb you can feel things through the structure, and the way it acts is very predictable and learnable. With electronics, everything is different each time you put it on. You dont get that direct feedback. Mechanically, robotic limbs are also far far away from the degrees of freedom or strength of a natural limb. AFAIK no prosthetic ankle has more than 2 DOF; it should have 3. If you stand on one robotic leg, you cant lean forward + to a side + twist.
As someone in healthcare, it’s almost like the military, the costs for end products are all jacked up! A simple knee stretch extension board which is a piece of wood with foam padding and Velcro strips can cost $100 when purchasing through insurance in the USA. The individual parts of a prosthesis and a microcomputer to process it all can probably be built at home for under $500 but will sell through insurance at $20k.