Because there is so much moisture in the turkey burgers, they can be much more fragile before cooking than a beef burger. It's important to use higher fat ground turkey (i.e, ~85% lean). The egg will act as a binder as the burgers cook, but sometimes ground turkey has too much added a water. If your burger mix is too moist to form into patties easily, toss in a handful (¼-⅓ cup) bread crumbs to absorb some of the moisture and allow them to maintain their shape.