5-Year Global Study on MAST™ Minimally Invasive Fusion Procedures to Treat Degenerative Lumbar Spine (MASTERS-D2)

In this Prospective, Global (multi center), Post Market Release (PMR) Study, Patients will be submitted to a single or double level instrumented fusion procedure using a PLIF, TLIF, ALIF, OLIF, DLIF or MIDLF technique via a minimally invasive procedure and will receive the same medical treatment as if they would not participate in this study. * The study will be monitored with visits conducted at the start, during and at the closure of the clinical study. * MedDRA coding will be used to classify the Adverse Event. * The study will be conducted according to Medtronic SOPs * Sample size calculation: Assuming that the standard deviation for ODI improvement at 3 months is 20 for both groups (anterolateral and posterior) and there is no difference in the mean ODI improvement at 3 months, with 80% power and 5% alpha level, the sample size for the primary endpoint (DDD patients operated for spondylolisthesis) is as follows in order to claim equivalence between two groups with equivalent margin (-10, 10): * Estimated sample size per group (anterolateral procedures versus posterior procedures): 70 * Estimated total sample size for spondylolisthesis patients: 140 * From the MASTERS-D study it is know that approximately 50% of the patients with degenerative disc disease have spondylolisthesis ≥ grade I. Hence the required total sample size is 140/0.5 = 280. The study is anticipated to enroll 350 patients. * In addition to a final statistical analysis, 3 months and annual interim analyses are anticipated. * The study hypothesis for the primary objective is to verify whether patients operated for spondylolisthesis (≥ grade I) have equivalent mean improvement of ODI at 3 months regardless of the minimally invasive surgical procedure (anterolateral or posterior) used. * The null-hypothesis: Ho: Δ ODI\_Anterolateral ≠ Δ ODI\_posterior * will be tested against the alternative hypothesis: HA: Δ ODI\_Anterolateral = Δ ODI\_posterior Where Δ ODI\_Anterolateral is the average improvement in ODI score (baseline - 3 months) in spondylolisthesis subjects treated with the anterolateral approach and Δ ODI\_posterior is the average improvement in ODI score (baseline - 3 months) in spondylolisthesis subjects treated with the posterior approach.