JOIN USA neighbour had to smash through the woman's front door and throw a garbage bin at the animal to stop the brutal attack, which left the victim with horrifying injuries in the town of Portland, west of Melbourne.
"The neighbour actually came straight in and beat the dog away with a bin. That's probably saved her life," paramedic Justin Nunan told the AAP newswire.
"She sustained really quite severe injuries to her arm and face," he added.
"We have no understanding of why the dog attacked, it was completely unprovoked."
The 67-year-old was airlifted to Melbourne for surgery to reattach nerves and restore circulation to her right arm, which suffered major muscle and skin damage, emergency services said. If unsuccessful, the woman could lose the limb.
She also sustained major injuries to her left arm. "She was fully aware and conscious and very distressed," Nunan said.
The male pit bull-staffordshire cross, a family pet, was destroyed by council rangers at the scene.