Occipital condyles

The occipital condyles are undersurface protuberances of the occipital bone in vertebrates, which function in articulation with the superior facets of the atlas vertebra. The condyles are oval or reniform (kidney-shaped) in shape, and their anterior extremities, directed forward and medialward, are closer together than their posterior, and encroach on the basilar portion of the bone; the posterior extremities extend back to the level of the middle of the foramen magnum. The articular surfaces of the condyles are convex from before backward and from side to side, and look downward and lateralward. To their margins are attached the capsules of the atlanto-occipital joints, and on the medial side of each is a rough impression or tubercle for the alar ligament. At the base of either condyle the bone is tunnelled by a short canal, the hypoglossal canal. Fracture of an occipital condyle may occur in isolation, or as part of a more extended basilar skull fracture. Isolated condyle fracture is a type of craniocervical injury. The classification of Anderson and Montesano distinguishes three types of occipital condyle fracture: Type I: Isotated impaction fracture of the occipital condyle, due to compression by the atlas or dens. This injury is usually stable; significant displacement of fragments is rare. Type II: Occipital basilar skull fracture extending into the condyle, resulting from direct trauma. The craniocervical junction usually stays stable, but neurologic injury may occur from the blow to the head. Type III: Isolated avulsion of the condyle with displacement towards the alar ligament, due to forced rotation / lateral bending. This injury tends to be unstable and may co-occur with atlanto-occipital subluxation or dislocation. Neurological injury may occur and range from minor to instantly fatal. Minimally displaced fractures are treated conservatively. Surgery may become necessary if there is significant compression of the brainstem, spinal cord, the lower cranial nerves or cervical arteries. Bilateral condyle fractures (e.