My fascination with artificial arms dates to 1950 or so when the Dick Tracy comic strip featured a villain named Dr. Keenan Plain, whose claim to crime was his rather unorthodox use of an artificial arm. Normally a hand-shaped device on a rod slipped into a receptacle on the wrist. The prosthesis was totally cosmetic as there were no devices to power the hand, and it could perform only the simplest functions, such as holding a cigarette between a pair of plastic fingers.
Dr. Plain had built a flame thrower device that could slip into the forearm when the hand was removed. The nozzle had some action that when struck would result in the flammable material being ejected as a flint scratched to ignite the material. The doctor would stand by a roadside and ignite his flame thrower and would then rob unsuspecting good samaritans who saw the spectacle of a man's arm burning as they approached in their cars.
The artist, Chester Gould*, created some unforgettable (and somewhat clinical) drawings and wrote about such things as a leather bushing and other appurtenances relating to prosthetic hands.
I was about nine or ten at the time and have ever since did casual research on the topic, culminating in surfing the web for articles on the topic.
The other day I was watching Roger Moore in his first James Bond film, Live and Let Die. One of the baddies is Teehee, a rough guy who had lost his entire arm to a crocodile and was now outfitted with an artificial arm. I actually had to watch the film twice as I lost track of the plotline several times during the first viewing due to laughing so hard at the parody of an artificial arm wearer in the Teehee character.
There are several visual cues that aren't consistent with the usual artificial devices. The most obvious is the extra length of the right arm, even to the extent that the arms of the jackets worn were specially tailored to accommodate a prop hook held by a natural hand.
Another obvious mistake is the frequent wrist movements - flexion and extension, yet when the arm is exposed at the end there is no visible means of moving the wrist. The movements are simply by an actor who is gripping a claw inside the jacket sleeve.
The funniest, to me, was when Teehee took Bond's gun and, while held in both flesh and metal hands, proceeded to twist and bend it. Now everyone can try this experiment: get a one or two foot length of 1/2" pipe. Grip it in one hand, then use a pair of vise-grips to grasp the other end of the pipe. Now try to bend it. What did you discover? Right, you just can't do it. Now someone who had two artificial hands _just might_ do this if there was a powerful enough hydraulically-driven gear in the wrist. And even that scenario would require the upper wrists (or arms or shoulder...) to be secured to something stronger than flesh and bone.
(This same principle exposed the total unworkability of the Lee Majors character in The Six Million Dollar Man, who routinely lifted cars using his bionic arm. Imagine putting a hydraulic jack in your left hand, stick it under your car, then start pumping the jack. Your arm and shoulder just aren't strong enough to hold that jack against the weight of the car. Same thing if you strap said jack against your shoulder. Your body just won't live up to the promise (or premise) of the story.)
At the end of the film, it's obvious that TeeHee needs a better tailor as somehow his whole jacket sleeve comes loose during a fight with Bond. Here you see this massive full metal arm that must weigh in at 20 pounds if it weighs an ounce. I'm guessing that a natural arm is about five pounds. That means that Teehee is lugging the equivalent of a bowling ball around all the time, this extra weight hanging from his shoulder by means of a harness. By the way, for actual wearers of upper limb prostheses, the harness is fitted with cables that, through shoulder and chest movement, flex the gripping part of the "hand," usually a bifurcated hook device that is kept closed by a broad rubber band.
All of this use of a prop metal arm got me to remembering a heavy in an earlier film, Charade. The villain in this case, Herman Scobie, was played by George Kennedy. At one point Scobie corners hero Carson Dyle, played by Cary Grant in a stairwell, and needs to tie him up. In order to keep Dyle covered, Scobie transfers the gun from his human left hand to his hook right hand (at least he makes a very believable thrust forward with his left arm to open the hook). Once again the hero, for the sake of the plot, ignores the fact that the claw can't pull the trigger.
Check out the screen shots from both movies in my gallery here.
*I always chuckle when I recall a Mad Magazine sendup of Dick Tracy, "written" by one Chesterfield Oldgold. Chesterfield and Old Gold were popular cigarettes of the day.