Ah! The crabcake school of pattie manufacture!
The Cheasapeake basin has some of the best crab in the world, and so crabcakes are a local favorite.
Crabcakes need some filler to make the meat stick together. If you're ever in the region, ask the locals where to go for the meatiest crabcakes. They will know which of the dozens of local eateries give you bread crumbs with Old Bay seasoning and onions, and which ones give you chunks of backfin.
I have to confess, I put an egg in two pounds of ground round if it's going on the grill. Nothing else. The burgers don't shrink up or crumble so much that way.