Adjacent level disease-background and update based on disc replacement data

The precise etiology of adjacent segment disease following cervical spine surgery is controversial. Theories for development include inevitable changes secondary to the natural progression of the degenerative cascade and changes secondary to altered biomechanics of the fused cervical spine. Motion preserving techniques, such as cervical disc arthroplasties (CDA), have been introduced with the hopes of reducing the rates of adjacent segment pathology. Recently, 7-year data from the investigational device exemption (IDE) studies have been published. The purpose of this review is to provide an update on cervical adjacent segment disease incorporating this emerging data into the analysis.

Although the 7-year data for CDA has confirmed continued success, specifically regarding improved neck pain and reduced re-operation rates, the influence of CDA on reducing rates of adjacent segment pathology remains questionable. Although some studies have found more radiographic adjacent segment disease after anterior cervical discectomy and fusion (ACDF) compared to CDA, an association between these findings and clinical symptoms has not been established. Cervical disc arthroplasty continues to outperform cervical disc fusion regarding some patient specific parameters, however, whether CDA reduces rates of radiographic and clinical adjacent segment pathology remains unknown. Without studies developed specifically to address this question, the answer remains elusive.