The only time they would hit the ground while growing would be if the elk was eating facing a hill, probably not frequently enough to make them grow differently.
Selective pressure would favor an antler that protected the face but then curved upward to keep another elk's antlers farther away since they fight each other with their noses pointed downward. Another selective issue would be that the bull's display is more obvious when the anlers go up than forward since they often face each other when challenging and an antler point facing toward you would not be as obvious as one that is skylined. And, if the brow tine got too long in the forward direction, it could actually hinder the procurement of food (eating) since they tend more toward grazing than browsing. The growth shape of an antler is genetically determined and may be altered due to nutritional factors or traumatic injuries but an occasional bumping of it on the ground is not likely to cause it to change shape.
