Britney Spears' new pet terrier is nursing a broken leg after the singer's young sons reportedly injured the dog. The pop star's kids, Jayden James and Sean Preston, were playing rough with the little dog, London, when he yelped in pain, according to U.S. reports. A source tells the National Enquirer, "When Britney first got the puppy, she showed him to the boys. "Sean chased the little dog until Britney finally had to stop him because the dog ran under the bed and wouldn't come out." But the boys' rough play continued - according to the Enquirer, they often threw little London around. And now the pooch is sporting a cast on his rear leg after one recent incident left him in agony. The source adds, "Britney found London under the crib whimpering and crying. "The poor puppy was taken to the vet when Britney's cousin Alli Sims noticed that he wasn't walking right or running as fast."