Real mountaineer behind 127 Hours movie shares gruesome details of how he amputated his own arm

Warning: This article contains graphic descriptions which some readers may find distressing.

Mountaineer Aron Ralson has opened up about what it was like being forced to amputate his own arm in a bid to get free from a canyon.

In April 2003, Aron Ralston was climbing in Bluejohn Canyon in southeastern Utah, when he accidentally dislodged a boulder and his arm became trapped.

After being stuck there for five days, having made his way through his food and water rations and unable to call for help, then-27-year-old Ralston made an impossible decision to cut himself free.

On the sixth day, Ralston saw the arm trapped by the boulder had begun to decompose and after accidentally slicing the tip of his thumb while trying to chip away at the boulder, he had a sudden realization.

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 continued: "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."

Ralston decided to take drastic action on day six of being trapped (TLC)

Ralston noted hearing the alarming sound 'threw [him] into a panic' and went further than just 'scaring' him.

"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," he continued.

And as he was 'twisting [himself] around trying to slide [his] arm up and down' suddenly it 'came to' him.

"This epiphany, that I could break the bones because my arm was caught so tightly that I could torque myself."

Using his body weight, Ralston slammed himself against the opposite wall of the canyon snapping both the bones with the sound reverberating throughout the valley.

Thankfully, they broke in the same spot close to the engineer’s wrist.

Aron Ralston's story inspired the movie 127 Hours starring James Franco (Samir Hussein/Getty Images)

"I said to myself, here we go Aron – you’re in it now. And then, I took my knife,” he explained.

Using this and handmade tourniquet, he was able to cut through the remaining nerves and muscle.

Ralston describe the sensation of freeing himself like a ‘fire’, which spread throughout his arm but eventually he escaped his ordeal.

He said: "I fell down and I was free…it was the happiest moment of my life. There will never be a more powerful experience for me.” He stated tearfully, during the interview.

The events of that fateful April would later inspire an autobiography and a feature film, 127 Hours, starring James Franco.