My heart breaks for you and your mother. This is very close to my own heart also. I have to speak out. I am so fed up with how our medical system runs in this country. If your mother agreed to the surgery and wanted to take a chance, then she should have been allowed to make that decision and not have it dictated to by a doctor. Equally as maddening as this is, Why bother suggesting this to her and then saying, nup sorry she's too weak? Its irresponsible and incredibly insensitive.
You won't be suprised to learn, that your healthcare, my healthcare isn't something we control ourselves, its in the hands of medical professionals via the govt, and they ultimately make the call. Your wishes are disregarded over their opinions. My late father was initially told they would replace his hip, then they decided not to, but to just put pins in his femur, meanwhile a hip replacement would have been a better option and would have given him less pain when the end came.
There is a dangerous mentality here within the medical profession that if you are too old, or terminally ill, you aren't worth performing procedures on and are treated like a second class citizen. They do give up and just shove palliative care down your throat as well as alot of painkillers giving those who are terminally ill a chance to die in a dinky little room under a morphined out cloud.
Palliative Care to some might be good, but its not good enough. Its a shame that healthcare isn't like the US, its not their job to make a moral call, if your 92 and want a hip replacement, you'll get it. Here they will do what they can to avoid it and tell you they are too old to have it (in other words, they decree that a 92 year old is not worth a hip replacement).
Palliative Care in this country is crap compared to the way its practiced and administered in the US and I'm not afraid to say it.
My advice to you, is to possibly seek another professional opinion by a completely different specialist. Someone that is prepared to work with you and your mother.
I wish you all the best