No fighting. Just roll once, roll twice.
Category: ANPPN Activites of No Particular Prosthetic Need
Torque values for prosthetic arms and lifting weights when considering forearm osseointegration [estimation]
Currently, socket technology appears to have a technical competitor, at least in theory, and that is "osseointegration".
There, the prosthetic terminal device - hand, hook - is mounted on a bolt that sticks through the stump's skin and resides inside the stump's bone. With sockets, a liner, embracing type of socket, straps or vacuum type principle is used to keep a socket in place, that is attached to the remaining components of the prosthetic limb.
Some drawbacks of osseointegration include that the bolt has to be implanted surgically over a series of several operations, that the skin will provide a chronic wound that carries the permanent risk of infection, that the bolt or stump's bone are relatively brittle and thus can and will break as they broke in the past, that many repairs then involve surgery rather than just a prosthetic technician, as well as temperature sensitivity particularly to cold temperatures. Also, most health insurances might not cover the procedure nor its complications or after care, so one requires some 80'000 USD for the operation, then more money for all the rest, essentially pointing to a privately paid 150'000 to 300'000 USD expense with no guarantee of function.
The advertising promotes bolt implants or "osseointegration" by suggesting that sockets are a main problem of discomfort and hygienic problems. Comparing between both systems, it would be honest to say that one needs to clean equipment and skin frequently anyway. With the efforts one must provide to clean an osseointegration wound many times a day using special disinfecting solutions, one can also keep a prosthetic socket and liner clean. In other words, who cannot keep a socket clean also might be a candidate for implant infections.
That aside, I cannot see how my normal life (outside wearing a prosthetic arm) could survive with a hard bolt sticking out of my otherwise (mostly) soft body surface (other people actually complain about any hard metal type material anywhere around, so, no bolts due to intimacy reasons to begin with).
Furthermore, I have relatively bad circulation on my stump, in such a way that it needs compression all the time anyway. And with that, I am (in fact) better off with wearing tight sockets rather than no sockets - for simple reasons of circulation and associated stump and phantom pain.
When one considers the metric performances that one would wish to achieve with an arm, or more interestingly here, a prosthetic arm, one might want to take actual facts into account. Such as: what type of forces (in terms of numbers and figures) might we be looking at.
Upper extremities and prosthetic options are getting it from left and right these days. So what are we going to believe? As I am currently suffering from post traumatic instability in my left wrist and elbow (the "healthy" arm), working the hard parts of life with my prosthetic arm become a real very day issue. Now, negotiating single grams is not an option any more.
For the most part, osseointegrated bolts may be nice to wave a prosthetic arm around the office. But it appears that the fun ends there. Since a considerable while now, some outspoken members of the osseointegrated community had been invited several times by me to provide videos demonstrating how they lift some usefully heavy 25 kg bags or more or such, but no such demonstration so far has been provided so far. In fact, we even lack a side by side comparison in how osseointegrating an arm stump will in any way improve ADL (activities of daily living). So the ratio of C (cost) over V (number of videos that provide proof of superior force and ADL function) C/V is indefinitely high for the osseointegration of arms application.
Because, it is about overuse. Suspecting also that the world's most proverbially notorious osseointegrated patient admits to suffering from overuse of his other extremity himself already points to a serious flaw in just how much (read: how little) an osseointegrated bolt will accept in terms of (ab)use. So the C/V ratio is estimated to be so high for good reason: there is no actual function that osseointegration gives "back". Furthermore, even pulling a regular Becker hand's cables might just be too much for these bolts which is an assumption from other backchatter, pointing at failure risk levels around 5 kg just from that. So much for the anecdotal bits.
Real life has numbers and costs attached to it.
After all and in the long run, there is just one thing that we could keep in mind for being the real reason why we would like to wear prosthetic arms (if not for additional reasons): to prevent overuse of the other arm by any means conceivable. Not to dance for the public, to expose one's armpit or wave around passive weights with the goal of wearing some arm without real function. And to work towards overuse prevention, extensive mechanical vibrations, serious blows and hits, strong pulls and torques, high repetitions and high loads, simple but reliable function, and tight control options are what a prosthetic arm needs to be primarily built for. Not shee shee froo froo pantsy boy demonstrations like "I can hold a water bottle" or "I can hold a tooth brush" but lifting a table, moving a shelf. moving 20 filled up box moving containers, scrubbing a toilet or shower, wood working, actually getting some real stuff done.
To provide minimal symmetry for posture demanding tasks such as typing, choosing a bionic or other myoelectric arm is an error! The correct answer is to wear a light weight and vibration insensitive arm with either a hook or a hand, that may be equipped with a pencil. My favorites here are my passive arm or the hook.
To provide reliable support for garden tools, high pressure cleaning or vacuum cleaning, ironing or other manually tasking work, the Becker hand or a hook proved to be best.
Personally, I have ripped out wrists from their prosthetic socket mount, I have ripped off 1,5 mm steel cables due to poor mount points, and I have irreversibly damaged prosthetic wrists or prosthetic hands built by lesser able companies. Now, I wear my own customized body powered arm, I use a Puppchen wrist, I wear Alpha gel liners, and I routinely pull and lift weights of up to 25-30 kg, occasionally up to 40 kg. And that is not considering sports.
So, figures now.
Of course one can spend all day theoretically analyzing grip options and comparing different options or, just do it.
It is intriguing to see recent surges of apparent ADL (activity of daily living) demonstrated with so-called "bionic hands" (including Otto Bock Michelangelo hand, iLimb by TouchBionics and BeBionic by RSL Steeper). For the most part, these are not a demonstration of a need to wear any of these hands.
There are people that realize that not all advertising really means the offered solution works. Hand transplants - as useful or useless as some of the new 'bionic' hand gadgets - are known to fail and some people take a while before they verbally and publicly admit that body powered hooks are not as bad after all. As Jeff Kepner said in a video interview - with a hook you know what to expect. The difference still is that 'bionic' hands can be put aside - whereas hand transplants cannot.
Stories like that makes you consider however just how much can be done without ANY prosthetic or transplanted hand. Just to get a feel for the functionality and to fully feel with the extremity.
Videos are at least somewhat non-negotiable, and therein lies their beauty. Conversely you will hate me for the simplicity of (at least some of) these. So below is a demo of actual ADL using the arm stump only. Any of these may be also carried out with a prosthetic arm, but in many instances they work a lot better with 'just' the stump. Old orthopedic surgeons used to say "the best prosthetic arm is the stump itself" and it seems that the extra time my surgeon spent on my arm to fix it up proper and neat was time well spent. I find that the stump he left we with is in fact useful - long enough and sensitive.
"Bionic" prostheses Activities of Daily Living and Sports ANPPN Activites of No Particular Prosthetic Need Household Prosthetics Specifications and comparisons Tricks and techniques Tricks one handed Tricks with stump