Arcuate foramen: In human anatomy, arcuate foramen, also known as ponticulus posticus (Latin for "little posterior bridge"), refers to a bony bridge on the atlas (C1 vertebra) that covers the groove for the vertebral artery. It is a common anatomical variation and estimated to occur in approximately 3-15% of the population.Anterior atlantooccipital membrane: The anterior atlantooccipital membrane (anterior atlantooccipital ligament) is broad and composed of densely woven fibers, which pass between the anterior margin of the foramen magnum above, and the upper border of the anterior arch of the atlas below.Spinal fractureHerbert screw: The Herbert screw (invented by Timothy Herbert) is a variable pitch cannulated screw typically made from titanium for its stainless properties as the screw is normally intended to remain in the patient indefinitely. It became generally available in 1978.Cervical fractureInterbody fusion cage: An interbody fusion cage (colloquially known as a "spine cage") is a prosthesis used in spinal fusion procedures to maintain foraminal height and decompression. They are cylindrical or square-shaped devices, and usually threaded.Dense artery sign: In medicine, the dense artery sign or hyperdense artery sign is a radiologic sign seen on computer tomography (CT) scans suggestive of early ischemic stroke. In earlier studies of medical imaging in patients with strokes, it was the earliest sign of ischemic stroke in a significant minority of cases.