A medical system includes parts used in a method for detachably establishing a spatial orientation between a body implant and an aiming device. A positioning arm being connected to the aiming device and an adaptor device being connected to or integrally formed with a bone stabilizing plate are hooked into each other. This is accomplished by means of an engaging element of the positioning arm, which engaging element is designed such that it may be coupled with an attachment element of the adaptor device. Further, there is provided a snapping mechanism which is designed to automatically engage in an interlocking element of the adaptor device, when the positioning arm, when hooked into the adaptor device, is rotated relative to the adaptor device towards a final angular position.