The one drawback to taking Elena from behind, was that Damon couldn't really use compulsion, without his intention being very clear before it occurred. He wanted to hear her, to hear every little whimper and cry, and if he couldn't compel the sounds from her, he would fuck them out of her.
Damon's fingers found his slave's nipple easily, even through her top, twisting his fingers around it gently, but firmly, as he pounded into her. He had no doubt there would be bruises for her after, if he didn't give her any of his blood.