Sturm came charging at his opponent from the very start, and downed Barker twice in the second round, prompting trainer Tony Sims to throw in the towel.
And after the bout it emerged that the 31-year-old Barker, making his first title defence, had dislocated one of his hips as he threw a punch in the opening round.
Sims was devastated at Barker's plight.
"It's a disaster - you'll probably never see him in the ring again," said the trainer.
"His hip went in the first round when he threw a right hand. He came back to the corner and said 'I think it's gone, it's hurting me'.
"In the second round he got clipped with a shot and - I don't know what's happened - it's completely gone on him. I was hoping it would just be a muscle injury but when he went down the next time I threw the towel in because I knew he couldn't move.
"He's had problems with his hips before and they're just not right. He'll have an X-ray at the hospital and we'll see what's happening from there."
Sturm was thrilled with his showing in what was the 20th world title bout of his career.
"That was the second best performance behind my loss to Oscar de la Hoya," said the 34-year-old.
"I wanted to start fast but Darren caught me with a left hook and it was hard. I'm 34 not 44. Every human is different and I feel great.
"I am training like never before and I think I can go on for another 10, 12, 14 fights."
The fight contract included a re-match clause, and Sturm confirmed after the fight that he would be happy to face the British star again - should he be fit enough.
"He had some pain in his leg but hopefully he will be alright and we can have a rematch in London next year. You have to go back, it is the gentleman thing to do after he gave me a shot here."
Elsewhere, Enzo Maccarinelli beat veteran Courtney Fry in the seventh round of their bout at the Liverpool Echo Arena to defend his Commonwealth light heavyweight title.