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Implant Motion at Greater than 1-Year Follow-up in Multilevel Cervical Disc Arthroplasty Constructs

Introduction Cervical fusion alters the biomechanics of the cervical spine with adjacent levels compensating for the lost motion. If multiple levels are fused, then the compensatory motion is even greater at the nonfused levels. This may be associated with the development of symptomatic adjacent segment disease. In addition, through motion preservation, postoperative morbidity associated with multilevel surgery is reduced—a single transverse anterior incision can be used, less pain is associated with posterior approach, and no collar or motion restrictions. Multilevel cervical disc arthroplasty is therefore an alternative to fusion to preserve motion and reduce the incidence of recurrence of symptomatic disease. Materials and Methods Lateral flexion and extension radiographs were analyzed for motion at the level of the disc arthroplasty using the posterior vertebral body angle. The difference between the posterior vertebral body angle in flexion and extension was taken. We classified any disc that had less than 2 degrees change in angle not to be exhibiting motion. Results Postoperative radiographs of 100 patients (59 two level, 34 three level, 7 four level) who had undergone anterior cervical decompression and cervical arthroplasty at two, three, or four levels with at least 1 year radiographic follow-up were reviewed. Radiographic data were available for 239 discs: 77% (n = 185) of discs maintained motion of greater than 2 degrees. Average follow-up in this group was 94 (range, 52-291) weeks. In the group of 54 discs that exhibited less than 2 degrees, motion average follow-up was 110 (range, 54-291) weeks. In seven two-level constructs and in one three-level construct, all replaced levels showed less than 2 degrees of motion. Conclusion Multilevel cervical disc arthroplasty provides a viable option for maintaining motion at operated levels beyond 1 year and therefore may reduce the potential for symptomatic adjacent segment disease. Disclosure of Interest None declared