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 osteophytes 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.