'X-Factor' 911 Stagehand 'Cracked Head Open' Before 50 Cent Performance

1/28/2012 5:00 AM PST

50 Cent's performance on "X-Factor" last month was a bloody mess behind the scenes -- with one stagehand smashing his head open after falling off the stage ... this according to the 911 call obtained by TMZ.
The accident occurred just as Fiddy took the stage to perform two songs (below). According to reports, a stair riser crashed down on several stagehands ... striking two on the head and one on the elbow.

As a result of the accident, according to the 911 call, one man fell off the stage and "cracked his head open."

Paramedics responded to the scene, treating the injured just feet away from 50 Cent's performance. All three stagehands were rushed to a nearby hospital for treatment.