Mid- or High-flex Rods Versus Low-flex Rods of SpineShape System IV for Treatment of Degenerative Lumbar Spine Diseases

Inclusion Criteria: * degenerative symptoms in 1 to 2 segments in the lumbar spine L1-S1 * signed informed consent of participant * confirmation of the participant that the attendance of follow-up visits are intended * Body-Mass-Index \< 32 * Pedicle screw axis distance \< 30mm * one or more of the following indications: * (dynamic) stenosis in the spinal canal * neuroforaminal stenosis * facet joint syndrome / spondylarthrosis * discopathy (recurrent disc hernia) * degenerative spondylolisthesis (Meyerding \<1) * instability (hypermobility with antelishtesis, hypomobility with retrolisthesis if decompressed) Exclusion Criteria: * missing bone structure, e.g. due to congenital anomalies or sever anatomical deformities that make anchoring of the implant impossible * damaged structural tissue, e.g. due to a bone fracture * application to the thoracic or cervical spine * pronounced idiopathic scoliosis * spondylolisthesis \> Meyerding grad 1 * isthmic spondolylysis * bone tumor * osteochondrosis modic type I, II or III * osteoporosis, which could impair screw anchoring * history with third party implants * patients with an active local or systemic infection * known allergy to titatnium alloys * skeleton in growth (epiphyseal joints not closed) * severe muscular neuronal or vascular disease * immunosuppresive therapy * long-term therapy with cortisone * heavy smokers (regular consumption of more than six cigarettes per day), drug addicts and alcoholics * chronic p…