Found at the base of the occipital bone on the lower back portion of the skull, the occipital condyle is one of two kidney-shaped convex surfaces that articulate with the superior facets of the atlas bone. Each condyle is located to either side of the foramen magnum, the hole in the skull base through which the spinal cord enters the cranium. The shape of the occipital condyle allows for nodding and very slight lateral movements of the head.
To understand the function of the occipital condyle is helpful to know the anatomy of the atlas bone. Named for the Greek Titan Atlas because of its role in supporting the skull, the atlas bone is also known as C1 and is the uppermost of the cervical vertebrae. It is hollow, as the spinal cord passes through it, and features two bony structures that protrude laterally, one on either side. These structures are referred to as the lateral masses and are largely responsible for supporting the weight of the head on the neck.
The superior facets, each of which articulates with a corresponding occipital condyle on the occipital bone, are found on the lateral masses. These facets are concave or cup-like surfaces that fit with the rounded surfaces of the condyle, and their corresponding shapes allow the skull and atlas bone to slide back and forth against each other, making moving the head possible. Specifically, the joints found at each occipital condyle are the atlanto-occipital joints, condyloid or oval-shaped joints that allow flexion and extension, or nodding, of the head, and some lateral flexion, or bending side to side.
Fractures of the occipital condyle are not uncommon and are often the result of trauma to the neck. Such fractures are linear, appearing as a crack in the occipital bone, or compressed, with part of the surface of the condyle being pushed inward. Linear fractures are generally less severe, and recommended treatment typically involves wearing a neck brace or halo, which keeps the weight of the head off the vertebrae. This gives the bone a chance to heal as well as lessens the risk of spinal cord damage from contact with fractured bone.
Compressed fractures are more likely to put pressure on nearby tissues. Therefore, surgery may be required to repair the damage to the area without endangering the spinal cord. Mild compressed fractures may be treated like linear fractures, however, and allowed to heal passively with the assistance of a neck brace.