So, I'm on a bioengineering course, and we've been divided into groups. Each of the groups has been assigned a research project, and my group has one involving 3D printing and prostheses.
It's really interesting and, as a science nerd whose maternal grandfather was a transfemoral amputee, it feels amazing to be alive at a time of such great advancement.
However, I am also Bucky Barnes trash and get distracted easily, so this is not going to be a post about our research. There are plenty of actual science posts out there that can tell you this if you are interested, and do it a lot better than me. This is a post about me trying to answer the question that occurred to me in my first research session- what the hell did HYDRA attach to Bucky, and how did they do it? After all, in this case, the Metal Arm of Death and Badassery is basically just a super-advanced (and somewhat lethal) prosthesis. And although most attempts to work out What The Hell Is Up With The Metal Arm Of Death And Badassery focus on the techier side of things, I'm going to be different and look at this from the prosthetics angle.
First of all, what kind of prosthesis even is it? Obviously not a normal one, but there are four main types here in our reality- transtibial, transfemoral, transradial and transhumeral. Now, the first two do not apply here as these refer to the legs, so it's down to the last two. To work out which it is, we need to ascertain how much of his original left arm is actually still attached.
We know from flashbacks in TWS that the entire left forearm was ripped off in the fall, leaving what is probably an intact (albeit almost certainly damaged) humerus. This means that, in real life and with people who aren't HYDRA, only a transradial replacement would be required. However, when the metal arm is blasted off in Civil War, we see no blood, just sparks. This tells us that HYDRA must have amputated the remainder of the arm and replaced the entire limb with crazy-advanced cybernetics (which is a logical decision, given their aims), and so the Metal Arm of Death and Badassery is (or was) best described as transfemoral (meaning that the replacement consists of an uper and lower arm, including a prosthetic elbow joint). Probably not an exact fit, of course, but pretty close.
Now for Part Two: what is it? Since it appears to be operated in exactly the same way as the right arm, with no cables, it definitely isn't body-powered. I therefore thought it might be myoelectric. In the real world, this refers to prostheses that use electrical signals from the remainder of the limb to operate. However, not only is there probably very little of the original left arm there, but myoelectric prostheses cannot get wet or dirty. Given that HYDRA set out to create the Most Awesome Assassin Ever (or something), there's no way they would have attached something with so many handicaps. It's perfectly serviceable in the real world under ordinary circumstances, but this is science fiction and these are not ordinary circumstances. These are super-soldier assassinating circumstances. Besides, given that Bucky follows Steve into a large body of water with no obvious loss of function, we know it can't be myoelectric.
Or can it? It's definitely more advanced hardware than we have right now anyway, and HYDRA did have access to an Asgardian power source. Perhaps in thirty years or so our real-world bioengineers will come up with a myoelectric limb that can withstand water or dirt. It's theoretically possible. In this case, however, I'm going into Sci-Fi Weirdness mode. I'll guess at some kind of integration with the nervous system. Since cybernetics have not actually come up in my research (which was supposed to be on 3D printing), I cannot speak on this. Maybe there's a better explanation combined with that area of technology. Someday I'll probably do some research and make a Part Two of this post focusing on the cybernetics angle rather than the prosthetics angle. It'll probably be more logical.
And finally, how is it attached? We're going to assume it's surgically attached, and over the course of my research I only found one method like this. Osseointegration is the natural fusion of bone and a titanium implant. Titanium is strong, lightweight and generally pretty awesome - if I was a HYDRA scientist trying to engineer a Metal Arm of Death and Badassery I'd probably use some kind of titanium alloy. (Because this is Marvel, I'd probably try and get some vibranium in there too, but that is not important right now.)
However, if we accept the hypothesis that there is nothing left of Bucky's original humerus, this is almost certainly not the method HYDRA used. If we do not accept that hypothesis, osseointegration is still an impossibility. This is for the simple reason that titanium is a hell of a lot stronger than our pathetic calcium phosphate skeletons. This means that anyone with an osseointegrated prosthesis can't put too much strain on it in case the bone shatters. The Winter Soldier uses the Metal Arm of Death and Badassery as a brake and to rip car steering wheels out. I think that's the definition of What Not To Do With Your Osseointegrated Prosthesis.
I did, however, once see a very interesting post on Tumblr that posited that, in order to anchor the Metal Arm of Death and Badassery, a significant amount of muscle and tendons would have had to have been replaced with metal as well. There were images and everything. Sadly, I do not know how to find this post, but it seems like the most likely explanation.
And finally, a short coda. Remember how Bucky's first real non-murdery scene in Civil War is of him handling soft fruit without squishing it, implying at least a rudimentary level of sensation? That isn't science fiction. That's science fact. During the course of my research, I learned about a guy with a bionic hand with sensors (or electrodes; my memory is fuzzy and this really isn't my area of expertise) that allowed him to distinguish a wide variety of textures and pressure. Pretty awesome, right?
All in all, perhaps it's better not to overthink this. On the other hand, maybe I've cleared something up. At the very least, I've proved one thing: HYDRA had better bioengineers in the nineteen-forties than we do today. If this were real life, I would be deeply concerned.
