Mix egg, mayonnaise, green onions, Old Bay and hot sauce in a small bowl until mayo is completely incorporated, then set aside.
Lightly break up crabmeat in a medium bowl. Add milk; toss gently to coat. Add crushed saltines; toss gently to combine. Add egg mixture; gently toss, once again, to combine. Using a 1/3-cup measuring cup, scoop up a portion of crab, forming the mixture into a very compact cake. Repeat to make 8 cakes (can be covered with plastic wrap and refrigerated up to 8 hours ahead).
About 10 minutes before serving, heat oil in a 12-inch skillet over medium to medium-high heat. Carefully add crab cakes; sautee turning once, until golden brown, about 3 minutes per side. Transfer to a paper towel-lined plate. Serve immediately with lemon wedges.