gms | German Medical Science

Objective: The aim of most new implants for cervical disc replacement is to maintain or restore function. In the past years there has been a large number of reports on advantages and disadvantages of cervical disc arthroplasty with prostheses. Limitations for the use of prostheses are restricted indications, secondary fusion, possible overdistraction and a number of design specific complications. The new Dynamic Cervical Implant (DCI) aims at combining the advantages of the easy and safe gold standard fusion-technique with those of the motion preservation philosophy. DCI has a limited motion range: it works like a shock absorbing spring and may help to slow down adjacent segment degeneration.

Methods: Between April 2007 and August 2008 26 patients (12 women and 14 men) aged 36 to 73 years were selected for motion preservation with DCI (Paradigm Spine) at either one or two levels (5 patients). Indications were radiculopathies (n=21), axial pain (n=2) or myelopathy (n=3) due to disc herniation or degeneration. Flexion/extension radiographs were obtained before treatment, at dismissal, and at 3, 6, and 12 months after surgery.

Results: Disc surgery was performed at C3/C4 (n=2), C4/5 (n=2), at C5/6 (n=13), and at C6/7 (n=14). In flexion/extension radiographs motion rapidly increased after surgery. However, five of 31 treated levels were fused (seen at 6/12 months). In 4 of 5 fused segments an implant of insufficient size had been used (initial phase trial). Implant sizes were changed and larger sizes are now provided. In one patient subsidence of the implant into the endplate was seen. Still, 87% of the patients rated their clinical result as excellent or good. There were no further implant related complications.

Conclusions: Disc replacement with DCI is a completely new strategy that is positioned in-between anterior cervical fusion and disc prosthesis. Up to now (date of abstract submission) we can only report about initial results in an early patient trial that is continuously followed up. Clinical results are as good as in anterior cervical fusion. Adjacent segment protection must be judged in future follow-ups, especially with regard to the high fusion rate in our early series. We will soon be able to answer the question whether the change of implant footprint has helped to reduce the fusion rate.