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

The purpose of this study is * to evaluate the effectiveness of MAST techniques for anterior/lateral and posterior approaches in Degenerative Disc Disease (DDD) patients with spondylolisthesis (≥ grade I). * To assess how single or double level MAST(Minimal Access Spinal Technologies) fusion procedures PLIF (Posterior Lumbar Interbody Fusion), TLIF (Transforaminal Lumbar Interbody Fusion), DLIF (Direct Lateral Interbody Fusion), OLIF (Oblique Lumbar Interbody Fusion), ALIF (Anterior Lumbar Interbody Fusion), or MIDLF (Midline Lumbar Interbody Fusion) are used in surgical practice and to describe long-term safety and effectiveness in a broad patient population of patients with degenerative lumbar disc disease .

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.