Trapped mountaineer who was forced to choose between cutting arm off or dying describes horrifying situation

This man knows more than a thing or two about being trapped between a rock and a hard place.

In fact, mountaineer Aron Ralston was the muse for Danny Boyle's blockbuster 127 Hours - which is certainly a film that is hard to forget.

Although you might have watched James Franco relive the horrifying ordeal in the 2010 flick, you might not have heard what it was like straight from the horse's mouth. So, take a look at this:

Although Franco might have done the role justice, listening to Ralston recalling how he dealt with the impossible decision of amputating his own arm or accepting death really makes the story hit home.

For those who are unfamiliar, the former mechanical engineer, now 48, had embarked on a solo descent of Bluejohn Canyon in Wayne County, Utah.

He had grown tired of being in the rat race while working for a big corporation and decided to ditch his job in 2002 to pursue his passion of climbing mountains and seeing the world.

Hence why he was out exploring the renowned slot canyon on 26 April, 2003.

While Ralston was making his way through the lower stretches of Bluejohn, a suspended boulder suddenly dislodged while he was climbing down from it.

Aron Ralston was stuck in Bluejohn Canyon for several days. (NBC)

Terrifyingly, it first smashed into his left hand, before pinning his right hand against the canyon wall - meaning he was completely stuck out in the middle of nowhere, with no way of alerting anyone.

For five days, the then-27-year-old slowly worked through his rations of food and water, but eventually had to rely on drinking his own urine to maintain hydration.

Ralston had carved his name, date of birth and presumed date of death into the sandstone canyon wall, as well as videotaping his last goodbyes to his family as no matter which way he tried, he could not free his arm.

Desperate times call for desperate measures

Despite severe dehydration, delirium and exhaustion, he decided on the sixth day that instead of accepting his doomed fate, he was going to take drastic action to save himself.

Ralston explained that he realised that his mangled arm had begun to decompose, so he realised it was now or never.

He had a couple of blades on him which he had been chipping away at the hefty 360kg boulder with, when his knife suddenly brushed the tip of his thumb - which led him to have a life-saving 'epiphany'.

In an interview with TLC recounting his miraculous escape, Ralston explained: "It ripped part of the skin off of my thumb, kind of like the way an old blister will rip away.

"And so that made me curious, and I started prodding around and I stuck the knife down in and at my thumb at that spot. It slid in like I was just sliding it into a pad of warm butter.

He revisited the exact spot where he nearly died on his 28th birthday. (TLC)

"It went in - I couldn't feel it of course - but it went in about a half inch and then this this hissing sound of gas, the decomposition gases releasing from inside my arm where they'd been building up, as my arm was decomposing over those five days.

"And that threw me into a panic, it scared me. It appalled me. It was a gruesome concept that my hand was decaying while still attached to my body and I started yanking my hand, my arm, and I was giving it everything that I had.

"I was twisting myself around trying to slide my arm up and down. It came to me, this epiphany, that I could break the bones because my arm was caught so tightly, that I could torque myself."

Brutal escape plan

Thanks to his engineering background, he knew that if he was able to snap his bones, he might be able to slip free.

Ralston continued: "I slammed my body against the opposite wall, I grabbed the back side of the boulder and even got my feet up to where I was standing halfway up the wall.

"Grabbing the backside of the rock and pumping my body over it until finally that bottom bone snapped.

"This 'pow' sound went kind of echoing through the canyon, and I don't even know if I started feeling excited at that point, but I just knew the next thing that I had to do was break the other bone.

"So I grabbed the bottom side of the rock and and pushed and tried to sink myself down until I was pushing up, to create the downward leverage on the top bone until it too made the same noise...pow.

James Franco starred in 127 Hours. (Warner Bros)

"It snapped in the same spot, thankfully. Right where my wrist was caught, they both broke right along here just just behind the bones of my wrist."

Although his blades were now bent and dull from days of chipping away at the rock, Ralston then began performing an amputation on his own arm - agonisingly slicing through muscle, an arteries and tendons.

He had fashioned a tourniquet out of the insulated lining of his water bottle.

His smaller knife, which was just two inches long, managed to do the trick - although he did have to use the other side of it to 'grab, twist and rip' through his skin.

Ralston then faced the hardest part yet - cutting through his nerve.

'It felt like fire'

He continued: "I was looking at the the nerve, this little strand of spaghetti running through my arm. I had to take the knife and pry it up - and even just when I touched it, it felt like fire. Or sticking my arm into a pot of liquid metal.

"It burned all the way up my arm and I took it again and lifted it up. I knew it was going to hurt. I plucked it up and did it in a motion and that that fire sensation redoubled and went all the way up to my shoulder.

"But I knew that was the hard part was over. And then boom, I wasn't even attached anymore. I fell down and I was free."

Fighting back tears, Ralston said although it might seem strange, he regards it as 'the happiest moment of his life'.

He added: "There will never be a more powerful experience for me, it was absolutely the greatest feeling to be to be given the chance to get out of here. Looking down the canyon, I knew I had a hell of a trip left.

Ralston went on to become a motivational speaker following his ordeal. (Gretel Daugherty/Getty Images)

"But at least I was not going to die right here. And the power of that, was astonishing."

Incredibly, Ralston then climbed out of the slot after freeing himself, rappelled down a 65ft wall and hiked out of Bluejohn Canyon before running into other mountaineers who alerted authorities.

He had lost a whopping 40lbs during the time he was trapped and 25 percent of his blood volume - but four hours after amputating his arm, the explorer was rescued and rushed to hospital.

Park authorities later enlisted 13 men who were armed with a winch and a hydraulic jack to move the boulder and retrieve Ralston's severed hand and forearm, which were then cremated and given to him.

For the TLC interview, he returned to the scene of the incident with a camera crew on his 28th birthday and scattered the ashes there, saying it was where they belonged.