Subsidence of cervical cages is a common problem. For the study, a new polyacrylmethacrylate cage was designed and prospectively implanted in patients with a mono- or bilevel cervical pathology. As control, a commercially available PEEK-cage was used, patients were randomized using minimization randomization, controlling for age and bone mineral densitiy. The investigators hypothesize that the newly developed cage has similar clinical and radiological qualities compared to the PEEK-cage, but at a much more favourable cost-performance ratio.

Inclusion Criteria:

• virgin spines
• no emergency operation
• age above 18
• sufficient knowledge of the German language
• indication for anterior cervical discectomy and fusion
• absence of concomitant spinal disease

Exclusion Criteria:

• prior cervical surgery
• indications other than ACDF
• concomitant neoplastic, metabolic, severe general or infectious disease