Design of a Novel Device to Provide Assured Seating of Bone Implanted Fiducial Markers

Abstract

Microstereotactic frames are a subset of stereotactic frames. They are smaller than traditional frames, and they employ small discrete anchors that are screwed into a patient’s bony anatomy, typically the skull. These anchors provide points of attachment for the frame and also serve as markers that provide a bridge between image space and physical space. Both these markers and the anatomy of interest are imaged in a CT or MRI scanner, and their positions are established relative to one another. The microstereotactic frame is then custom made so that, when it is attached to the anchors, it will guide a surgical instrument to an anatomical target. These frames offer advantages over stereotactic frames, including increased targeting accuracy and patient comfort. Firm placement of these anchors is critical as any movement will cause errors in the imaging localization, frame design, or frame attachment. Anchor placement is complicated by the variation in bone density and by the obscuring tissue and bleeding that make visual confirmation of seating very difficult. A novel device called the PosiSeat™ is presented that provides assured seating for bone-implanted anchors.