This paper presents an optical see-through augmented reality (OST-AR)-guided robotic system for spine procedures, integrating cone-beam CT (CBCT)-derived 3D spine models with live ultrasound for enhanced needle trajectory planning. The system enables in situ visualization of spinal structures, combining global anatomical context from CBCT with local real-time ultrasound feedback. A phantom user study with 16 participants evaluated facet joint injection and lumbar puncture procedures under AR vs. conventional screen visualization conditions, demonstrating the feasibility of AR-guided medical robotics for precise needle placement.