Adjacent Segment Degeneration after Cervical Disc Surgery: Comparison of One-Level Cervical Disc Arthroplasty versus Anterior Cervical Interbody Fusion: 7-Year Radiological Follow-Up

Abstract

Introduction Cervical disc arthroplasty and anterior cervical interbody fusion provide the same clinical result in the surgical treatment of degenerative disc disease. The main theoretical advantage of motion preservation is its preventive effect on the adjacent disc degeneration. The aim of our study was to compare the radiological results at the 7-year follow-up after disc replacement and after fusion. Patients and Methods Since January 2006 to December 2007, 17 patients underwent one-level cervical disc arthroplasty (group A), and 17 patients were operated with one-level interbody fusion (group B). ROM of the adjacent segment, dimensions of the adjacent intervertebral disc space, ROM and alignment of the whole cervical spine, and presence of heterotopic ossification were evaluated preoperatively and at 7-year follow-up. All the measurements were done by independent radiologist on the digital anteroposterior, lateral, and flexion/extension X-rays. Results The adjacent disc height decreased in both groups, but the decrease was more significant in the fusion group. Mean disc height was 4.13 mm (preoperative) and 4.03 mm (postoperative) in group A, and 4.02 mm (preoperative) and 3.83 mm (postoperative) in group B. The sagittal ROM of the adjacent segment was higher in the arthroplasty group (group A: 10.89 degrees, group B: 9.5 degrees). The cervical lordosis was significantly higher in the fusion group (group A: 11.81 degrees, group B: 18.59 degrees, p < 0.05). In the arthroplasty group, the mean ROM of the operated level was 11.4 degrees preoperatively and 11.12 degrees postoperatively ( p > 0.05). A total of 64.7% of the patients had any sign of heterotopic ossification. Conclusion The segment of the prosthesis ultimately showed preservation of the preoperative motion. The decrease of the intervertebral disc height, and the ROM (flexion/extension) in the adjacent segments was more significant in the fusion group, so the disc degeneration process seems to be faster after fusion than arthroplasty. The restoration of the lordosis is more effective with fusion than arthroplasty. The early experience is promising but long-term follow-up studies are required to prove the theoretical advantages of the arthroplasty in the prevention of the adjacent segment degeneration.