I think that distinctions should be made - and finer ones even than just saying: photography shall either be art, and in being that is very free to any artistic approach, or a representation of a (past) reality with should possibly serve some historical purposes later, even if "historical" only means reactions such as "Oh, you still had THOSE sofas back then?"
Its use is way too diversified to put itself into only either one or the other of two categories.
And the photographer as such is too much the personality who creates the image to have himself (herself, too!) pushed into the either/or-corner.
Some feel that photos should only represent a momentary slice of history. Which I think they should if DOCUMENTATION is the given assignment (as in photojournalism, for example). The photographers who work in the refinery where also my husband works must NEVER EVER change anything about their photos, since their photography (lots of it macro-photography of details of the plants) is to show EXACTLY the present state of a piece of refinery equipment. To become "artistic" on that would be criminal! (An example which is self-evident, isn't it?).
When you do portrait or wedding photography and work for clients, it may be their wish to get extra glamorous, extra soft, extra high-key, extra low-key, extra contrasty photos taken (produced) when "reality" was a normal day only, maybe made exceptional by the way the person dressed for the occasion (weddings are yet another very self-evident example for being kind of "extra" and going through a situation that is "special" and not the everyday reality). When out of artistic approach or upon request the photographer makes use of the filters he has in his case and softens the photo, or applies star-filters or whatever else there is, and set up lights and hair lights and one more here, arranges the bride's dress in a way I would never have fallen had she only just stopped and stayed, puts the person around her in a way they would never have been placed had he played "stop-action" with them, then he is already changing realities - in-camera this time. So wedding photography more often than not DOES change reality, produces something that goes BEYOND the exceptionality of the day as such.
And there may be other occasions in people's lives where photography cannot or should not be the either/or-thing. An anniversary where the old person wants to look their very, very best, although at 80 they might no longer do in reality, or the fact that before any film team could ever come into my house I would need to do a MAJOR cleaning and tidying job -that, too, would take me beyond my everyday reality

(too much time spent on too lengthy commentaries on TPF, that is why!!!).
So that said: if you do not want to show that this person (who I assume is in hospital and had been in hospital for quite long so he needed to get his hair cut in his hospital bed) is still so weak he cannot hold up his own head for long enough for his photo to be taken, but if you want to give both this person and the viewers the feeling that "he`s back here with us, he may still be in hospital but he will be back to being his old self" and the arm is disturbing, then take out the arm.
I personally find it disturbing because it does not REALLY look like an arm but like something that I see and think "Huh? What is THAT?"
I shall stop rambling abruptly now ... this has become too long, anyway.
(But, Alex, my own wedding photos ALL and exclusively are "captured reality", not one extra glamorous among them, for the extra glamorous wedding photography seems to be much more widely practised in the States).