Adjacent Segment Disease in Cervical Disc Arthroplasty
The rate, risk factors and consequence of adjacent level disease (ALD) in cervical disc arthroplasty (CDA) remains unclear. The purpose of this study is to determine the rate, risk factors and clinical outcome of ALD in CDA.
Methods: Retrospective review of 166 patients with a minimum five-year follow-up of a CDA was performed. Multi-level surgeries, including hybrid procedures, were included. Multiple implant types were included. The two inter-vertebral discs (IVD) cranial of the CDA were monitored for radiologic degeneration. No funding was attained for this study and the authors declare no conflict of interest.
Results: The rate of ALD in CDA was 28.3%, with most affecting the immediately adjacent IVD (27.4% and 7.6% respectively p=0.000). Age (p=0.209) and sex (p=0.201) did not relate to ALD, nor did preoperative degeneration (p=0.117) or spondylolisthesis (p=0.315) adjacent to the CDA. The number of operated levels (p=0.890), number of fused levels (p=0.354), implant alignment (0.255), ROM (p=0.569) and implant induced spondylolisthesis (p=0.402) did not affect the rate of ALD. However, fusion of the most cranial implant significantly increased the rate of ALD (p=0.032). The visual analogue pain scale (VAS) was significantly worse in those patients with ALD (VAS neck 2.7 versus 1.5 p=0.029; VAS arm 0.9 versus 2.3 p=0.002). The five-year functional outcomes were worse in those who developed ALD (NDI 20.1 versus 12.3 p=0.011). No patients required a reoperation during the course of this study.
Conclusion: ALD is common after CDA and worsens the patient’s functional outcome, but not their need for revision surgery within five years. Fusion of the most cranial implant is a major risk for developing ALD, whereas the initial implant alignment and function do not construe a risk.