Cervical motion segment replacement.

When symptoms bring to light a cervical spine degenerative disc process that requires surgical intervention, a symptom relieving procedure such as decompression, followed by functional restoration, arthroplasty, offers the benefit of prophylaxis of accelerated spondylosis at the operated level. In addition, by altering the biomechanical stress factors at adjacent levels, theoretically it should offer prophylactic benefit at these levels as well. The design requirements for a cervical disc prosthesis, the importance of precision instrumentation, and technique are described. Mechanical testing, animal testing, the study design for the EU clinical study, and the operative technique are discussed. The clinical 1- and 2-year data to date are presented.