A piston assembly is disclosed. In one aspect, the piston assembly includes a rotary piston, wherein the rotary piston comprises a first axis of rotation, a central bore having bore axis and at least two curved first constraint surfaces, and wherein the bore axis substantially corresponds to the first axis of rotation. The piston assembly also includes a substantially hollow-cylindrical bearing ring configured to be at least partially inserted in the central bore. The piston assembly further includes at least one fuse body configured to connect the rotary piston and the bearing ring, and to transmit, at least temporarily, a force in the two opposite axial directions relating to the first axis of rotation between the rotary piston and bearing ring.