Mix the beef, pork, breadcrumbs, Parmesan, egg, garlic, 1 teaspoon salt and pepper just until combined and roll into 32 one-inch meatballs.
Heat the oil in a skillet and brown the meatballs in 2 batches for 5 minutes, turning gently.
Place the meatballs, onion, carrots, broth and remaining salt in a 6-quart crockpot and cook covered on low for 5 hours until the meatballs reach 160°F.
Cook the pasta separately for 1 minute less than the package directs and drain it.
Stir the pasta and spinach into the soup and cook on high for 10 minutes until the spinach wilts.