"You placed the dog and the 9-year-old child in the confined environment of a caravan and returned to the party in the caravan nearby," he said.
"The scene you found I know will haunt you for the rest of your life and you have developed PTSD as a result of what you saw and experienced."
Frankie suffered 54 injuries and experienced major blood loss after the 54kg dog attacked him.
His mother, Willis, found her son's body after going to check on him. She ran out of the caravan screaming "my baby, my baby" as the alarm was raised, The Sun reports.
The court heard how Willis and Totterdell were drinking in a separate caravan and left the boy alone with the dog.
He was found dead at the scene after suffering serious injuries to his head and neck, including having one of his ears nearly severed.
The animal was put down on May 1 after the attack.
Outside court, Frankie's family described him as a "special young boy" who should never have been left alone.
"As Frankie's family, nothing will ever be enough, no sentence will ever be long enough," his Aunt Danielle Macritchie said.
"Not today, not tomorrow, not ever will we as a family forgive them for leaving our boy in a caravan with a dog he hardly knew.
"Frankie was left alone to die in the most horrific way, beyond anyone's imagination."
His father, Billy Macritchie said his world had "shattered into a million pieces" after his "baby" was lost.
"This should never have happened I wish I could hold you and kiss you forever. You are my whole life and now your (sic) gone.
"Sleep tight my darling boy, my best friend and my everything."
