This study is being undertaken to compare the clinical outcomes of patients that have unilateral posterolateral lumbar interbody fusion using a traditional open approach versus the MiLIF procedure based on the MiCOR Precision Bone Allograft, specialized Atavi instrumentation, and minimally invasive visualization capabilities.

This is a prospective, multi-center, non-randomized cohort design clinical study to evaluate the clinical outcomes of patients that have a minimally invasive lumbar interbody fusion (MiLIF) through the Atavi system compared to traditional unilateral open lumbar interbody fusion through a midline incision. the study will involve up to approximately 12 investigational sites and enroll up to 126 patients.

Inclusion Criteria:

• Patient is between 18 and 75 years of age

• Patient is scheduled for an elective spinal lumbar interbody single level fusion

• Patient is a candidate for posterior unilateral lumbar fusion through a midline incision

• Indication for surgery and dominant symptom of chronic low back and/or leg pain

• Diagnosis of one or more of the following:

  • Primary symptomatic degenerative disc disease confirmed with appropriate imaging studies and/or positive lumbar discography
  • Spondylolisthesis Grade I/II

• The affected motion segment reside in L2-S1 and are adjacent segments

• Patient, or authorized representative, signs a written Informed Consent form to participate in the study, prior to any study mandated determinations or procedure.

Exclusion Criteria:

• Patient has a known fracture in the lumbar spine
• Patient has systemic infection or evidence of any surgical site infection (superficial or organ space)
• Patient has compromised immune system or autoimmune disease (WBC<4000 or >20,000)
• Patient has uncontrolled diabetes
• Patient has a known malignancy
• Prior lumbar fusion attempt; prior laminectomy and/or discectomy are allowed
• Known medical or anatomical condition that would preclude a posterior lumbar fusion using metallic instrumentation (e.g., severe osteopenia)
• Patient with a planned placement of an electric bone stimulator
• Patient with a planned placement of indwelling epidural catheter for a long term pain management
• Patient is pregnant or wishes to become pregnant during the length of the study participation
• Patient is currently in litigation
• Patient is not likely to comply with the follow-up evaluation schedule
• Patient is participating in a clinical trial of another investigational drug or device.

Patients with chronic low back and/or leg pain who are candiates for elective lumbar interbody fusion through a postierior unilateral approach, that present to either group of surgeons, will be screened for inclusion in the study. If the patient meets all of the eligibility criteria, they wil be enrolled into the study and have either the MiLIF or open procedure depending on the surgoen they present to (i.e., what group their surgeon agreed to participate in).