Patient Registry to Observe Outcomes Following Implantation of the VariLift Interbody Fusion Device

Inclusion Criteria: * Patient is undergoing a procedure with unilateral or bilateral placement of VariLift * This is the first surgery at the index level * Patient has understood and signed the informed consent * Patient is skeletally mature Exclusion Criteria: * Revision Surgery * Is a Worker's Compensation Case * Infection at the operative site * Sustained trauma with instability * Sustained fracture of the vertebra at any of the lumbar spinal levels * Has a primary diagnosis of degenerative or isthmic spondylolisthesis greater than Grade 1 * Physically or mentally compromised (i.e., being currently treated for a psychiatric disorder, senile dementia, Alzheimer's disease, presence of alcohol or drug abuse) * Has a diagnosed systemic disease that would affect the subject's welfare or overall outcome of the clinical study (i.e., moderate to severe osteoporosis, Paget's disease, renal osteodystrophy, metastasis to vertebrae, adult onset diabetes, active rheumatoid arthritis, etc.) * Is an immunologically suppressed or receiving steroid in excess of usual doses * Is obese (as defined by a Body Mass Index (BMI) of \> 40 kg/m2 (BMI equals (weight in pounds x 703) / (height in inches x height in inches)) * Has disabling and daily narcotic dependency greater than 18 months * Has a known malignancy * Has a known allergy to metal implants