NTSB Factual Report

During pushback, the flight attendant stated that she was contacted by the lead flight attendant who asked if the crew rest area was secure. The attendant answered yes and looked to check again and found the door ajar. Fearing a passenger may have gone in she went over and climbed the stairs and checked the rest area. On her way down she believes she misplaced a foot on the narrow stairs and fell down breaking her arm in three places. After a few seconds she got up and contacted the lead attendant who contacted the captain and the aircraft was towed back to the gate.

NTSB Probable Cause

The flight attendant's inadvertent misstep on a ladder and falling during pushback resulting in serious injuries.