Inclusion Criteria:

The indication studied was degenerative disc disease (DDD) at a single level between C3 and C7 for any combination of disc herniation with radiculopathy, spondylotic radiculopathy, disc herniation with myelopathy, or spondylotic myelopathy.

The following additional inclusion criteria had to be present:

• At least 6 weeks unsuccessful conservative treatment, except in cases of myelopathy requiring immediate treatment (e.g., acute onset of clinically significant signs);
• Requirement for surgical treatment demonstrated by CT, myelography and CT, and/or MRI;
• Skeletally mature (≥ 21 years of age);
• Preoperative Neck Disability Index score of ≥ 30 and at least one clinical sign associated with level to be treated;
• Willing to sign informed consent and comply with protocol.

Exclusion Criteria:

Subjects were excluded if they had any of the following:

• Any of the following at the treated level:

  • Significant cervical anatomical deformity; e.g., ankylosing spondylitis, rheumatoid arthritis, etc.
  • Moderate to advanced spondylosis. Patients who demonstrate advanced degenerative changes. Such advanced changes are characterized by any one or combination of the following: bridging osteophytes, marked reduction or absence of motion, collapse of the intervertebral disc space of greater than 50% of its normal height;
  • Radiographic signs of subluxation greater than 3.5 mm;
  • Angulation of the disc space more than 11 degrees greater than adjacent segments;
  • Significant kyphotic deformity or significant reversal of lordosis;
• Axial neck pain as the solitary symptom;
• Previous cervical spine surgery;
• Metabolic bone disease, such as osteoporosis, defined as a BMD T-score equal to or worse than 2.5. If significant radiolucence is detected, a BMD scan in the spine, wrist, and femoral neck must be obtained.
• Active systemic infection or infection at the operative site;
• Known allergy or to titanium, polyurethane, or ethylene oxide residuals;
• Concomitant conditions requiring steroid treatment;
• Diabetes mellitus requiring daily insulin management;
• Extreme obesity, as defined by NIH Clinical Guidelines Body Mass Index;
• A medical condition that may interfere with the postoperative management program, such as advanced emphysema or Alzheimer’s disease;
• A medical condition that may result in patient death prior to study completion: unstable cardiac disease, active malignancy;
• Pregnant;
• Current or recent alcohol and/or drug abuser requiring intervention;
• Signs of being geographically unstable, such as recent or pending divorce, or high level of job dissatisfaction.