Comparison of Radiographic Fusion Rate and Clinical Outcome of ALIF and XLIF Performed With Either Recombinant Human Bone Morphogenetic Protein-2 or ViviGen®

Inclusion criteria: Patients who have an indication for a monosegmental ALIF procedure on the L5/S1 segment or a monosegmental XLIF procedure on L4/5 (both ALIF and XLIF procedure with or without an additional pedicular stabilisation), e.g., treating conditions such as spondylosis, spondylolisthesis and degenerative disc disorders with back and/or leg pain * Patients must be 18 - 70 years of age * Patients must have understood and signed the study information and the informed consent form * Patients are willing and able to complete scheduled follow-up evaluations / questionnaires as described in the Informed Consent Exclusion criteria: * Patients under 18 years and over 70 years of age * Patients with tumour / spine trauma / known bone disease / Parkinson's disease and similar CNS disorders / diseases or injuries of the peripheral nerves * Other procedures or segment than mentioned in the inclusion citeriaAdditional planed spine surgeries after index surgery * Current smoking * Pregnant or breastfeeding patients (or patient planning a pregnancy within one year after surgery) * Insufficient language skills in German * Inability to give informed consent * Refusal to participate in the study, unsigned study consent * Participation in another interventional study within the 30 days preceding and during the present study