A system for registering a patient's body part in a medical workspace of a medical navigation system is provided, wherein the body part is supported by at least one support device. The system includes a medical navigation system including a processor and memory, a reference device coupled to the at least one support device, a tracking device communicatively coupled to the medical navigation system and operative to determine a position of the reference device; an x-ray or fluoroscopic apparatus for capturing x-ray or fluoroscopic images of the body part; and logic stored in memory and executable by the processor. The logic includes logic that eliminates an effect of image artefacts on registration of the body part, wherein the artefacts are caused by the at least one support device.