In a 6-quart pressure cooker over high heat, frequently stir butter, onions, and garlic until onions are limp, about 3 minutes. Add rice and stir often until it is opaque, about 3 minutes longer. Add broth, wine, and 2 cups water. Stir occasionally until mixture boils, about 4 minutes.
Seal cooker. Following manufacturer's instructions, bring to maximum pressure (15 lb.); adjust heat to stabilize cooking rate. Cook 6 minutes. Release pressure quickly, running cold water over pan.
Open pan. Stir in crab, parmesan cheese, and sage. Add salt to taste.