Radiological and Clinical Efficacy of a Hybrid Spinal Implant ("Topping Off"): a Mono-center, Prospective Clinical Trial

Inclusion Criteria: * Informed consent * Legal capacity * Age ≥ 18 years * Indication for monosegmental lumbar spine fusion (PLIF or "topping-off ") L2-S1 with osteochondrosis Modic grades I-III or spondylolisthesis Meyerding grades I-III. * Radiologic signs of degeneration in the adjacent segment of the intended fusion without signs of instability Exclusion Criteria: * Motor deficit * Cauda equina syndrome * Previous surgical intervention of the lumbar spine * Relevant peripheral neuropathy * Acute denervation subsequent to a radiculopathy * Scoliosis with Cobb angle greater than 25° * Spondylolisthesis \> Meyerding grade III * Radiologic signs of degeneration in the adjacent segment of the intended fusion with signs of instability (for definition, see inclusion criteria) * No radiologic signs of degeneration in the adjacent segment of the intended fusion (for definition, see inclusion criteria) * Radiologic signs of degeneration in the adjacent segment of the intended fusion with \>Fujiwara grade II or \>Pfirrmann grade IV * Signs of instability in any lumbar spine segment other than that undergoing fusion * General contraindication for elective lumbar spine surgery * Pathologic fracture * Osteoporosis with pathologic fracture * Active systemic infection * Rheumatic disease * Disease of bone metabolism (e.g. Paget's Disease) * Bone metastasis * Local infection focus lumbar spine * Seizure disorder * Chronic ischemia Fontaine classification IIb-IV * Severe heart insufficiency (NYHA III-IV) * Blood coagulation disorder or blood thinning therapy * Cortisone intake more than one month in the last 12 months before randomization * Simultaneous participation in another clinical trial in the 30 days before randomization * Known allergy or intolerance to the implants * Dependency on investigator * Lack of familiarity with the German language * Placement in an institution by governmental or juridical advice * Absent legal capacity * Pregnancy