Comparison of Software-assisted Implantation of Elastic Spine Pad (TM) With Respect to Postoperative Change in Neck Disability Index (NDI) With the Conventional Disc Prosthesis Rotaio (TM) After Anterior Cervical Discectomy for Cervical Disc Prolapse

Inclusion Criteria: * Indication for monosegmental anterior cervical discectomy with implantation of a disc prosthesis Exclusion Criteria: * Radiologic signs of extensive bone degeneration in the affected segment * Necessity of implantation of a device smaller in height than 5 mm (as predicted with teh use of the Vertaplan (TM) software * Transversal spine cord lesion * Cervical myelopathy * Preceding surgery on the cervical spine * Traumatic lesions of the cervical spine * Radiographic instability in the affected segment: flexion / extension: shift sagittal plane\> 3.5 mm or 20% and rotation in the sagittal plane \> 20 °, OR in static X-ray examinations: shift in the sagittal plane 3.5 mm or 20% of the vertebral body width and relative sagittal plane angulation \> 11º * signs of instability (Olisthesis) in another segment of the cervical spine * Active systemic infection * diseases of the rheumatic type and all autoimmune diseases * bone metabolic diseases (for example, Paget's disease) * skeletal metastases * infections in the cervical spine * Neurological seizure disorders or other serious neurological disease with risk of falls * Severe heart failure (NYHA III-IV) * Bleeding disorders or clopidogrel / coumarins - treatment * Systemic use of corticosteroids for more than a month in the last 12 months * Pregnancy * Legally incompetent patient * Lactation * Deformity, anomalies, not fully developed skeleton * Local tumor disease * Pre-existing neurologic abnormalities or other shortcomings, such as a Parkinson's disease, diabetic neuropathy, multiple sclerosis, peripheral neuropathy * Drug / drug or alcohol dependence