Contraindications described by the [[FDA]] have included: isolated axial [[neck pain]], [[ankylosing spondylitis]] or [[pregnancy]], [[rheumatoid arthritis]], [[autoimmune disease]], [[diffuse idiopathic skeletal hyperostosis]], severe [[spondylosis]] with bridging [[osteophyte]]s or [[ossification of the posterior longitudinal ligament]], [[disc height]] loss > 50%, [[spinal infection]], [[metal allergy]] to components of the [[prosthesis]], severe [[osteoporosis]]/[[osteopenia]], active malignancy, metabolic bone disease, trauma, segmental instability, 3 or more levels requiring treatment, insulin-dependent [[diabetes]] mellitus, human immunodeficiency virus, [[hepatitis]] B/C, morbid [[obesity]], absence of motion (<2 degrees), and posterior facet arthrosis.