Danny Boyle’s new film 127 Hours recreates the nightmarish events that led up to Aron Ralston (portrayed with immense charm by James Franco)  cutting off his own arm in a mountain rock climbing accident. Ralston was trapped for 127 hours in a canyon in Utah when a falling boulder pinned his right arm to the canyon wall. Facing certain death, Ralston decided to do the unimaginable: he cut thru his forearm using a dull pocket knife in order to set himself free. He survived and became an international hero, a symbol of man’s can do spirit, a human being with an almost superhuman will to live, inspiring.

It’s a rousing a tale, but not one that is particularly cinematic or filled with any surprises. How much drama and action can you generate when the story is limited to one cramped location and everyone watching the film most certainly know its outcome? Boyle does his best by using lots of flashbacks, dream sequences, technical wizardry and a pounding techno soundtrack.

For the most part it works. The movie is not boring. It has its moments of heartbreak, humor and some very trippy imagery. But the real reason most people will be buying tickets to see 127 Hours is not for its artistry, but for its money shot: the arm cutting sequence. And they will not be let down. Ralston amputating his arm is done in graphic detail, it’s genuinely shocking, and Boyle uses visual effects and sound to make the scene borderline unbearable. The snapping of bones, Ralston’s screams, a special effect in which the viewer sees the knife doing its work from a perspective inside the arm, combine to make the amputation a gore classic.

While the movie strains to make deep spiritual and philosophic points, most of its highmindedness is lost in the sheer audacity of the arm cutting scene. And there ain’t no doubt that people will be talking about it. As much as the film explores Ralston’s soulsearching while being trapped, most of us are on the edge of our seats waiting for the money shot. With that in mind, Boyle, who also wrote the screenplay, tries to pump up emotions using the dream sequences and flashbacks, none of which really amount to much. But they are flashy. The cinematography by Enrique Chediak and Anthony Dod Mantle is stunning and Bollywood music genius A.R. Rahman’s pulsating score gives the movie a heartbeat. But all the razzle dazzle is dwarfed by a cheap penknife puncturing and tearing at human skin. Flesh and blood is the ultimate special effect.

This is a much better film than torture porn like Saw, but despite its good intention, 127 Hours achieves its biggest thrills through the same formula as many graphic horror films: showing us the most disgusting thing possible. And Boyle is such a talented director he manages to show it to us in newly visceral ways. When bones snap, they snap in superamped Dolby surround sound, with a searing bright flash of subliminal light jumping from the screen. In an effort to give the audience a sense of Ralston’s ordeal,  Boyle has chosen to subject his audience to its own endurance test, to try to give them a real sense of what it felt like to be Ralston in that moment of self-surgery.

Tonight’s screening of 127 Hours at the Austin Film Festival had the hardy film freak audience gasping, hiding their eyes and squirming in their seats. Ralston was in that cave for 127 hours and as much as Boyle tries to compress all of that suffering, soulsearching and fear into 95 minutes, the movie only really comes alive in those few minutes when it literally cuts to the bone.

127 Hours opens November 5 in the USA.