Adding to this, much like on a bat, dragon wings are ***generally*** attached at where the arm would normal be, but since they already have arms, they go above it. Connecting to the back would not allow them the leverage they'd need for take off when you think about the connects the muscle tissue would make to the pecs; the primary muscles in the upper body capable of flight.

Connections*

Jason simp you just got an anatomy lesson by a master do u feel special