Single-Level Cervical Artificial Disc Replacement Compared with Cage Screw Implants: 2-Year Clinical and Radiological Outcomes Especially Adjacent Level Ossification

STUDY DESIGN: Retrospective single-center, single-surgeon cohort study. PURPOSE: Our goal was to compare the 2-year clinical and radiological results of artificial disc replacement (ADR) and cage screw (CS) implants in patients with cervical degenerative disc disease (DDD). OVERVIEW OF LITERATURE: Anterior cervical discectomy and fusion with CS implants are an acceptable alternative to traditional cage-plate construct due to perceived decreased complications of dysphagia. However, patients may experience adjacent segment disease because of increased motion and intradiscal pressure. ADR is an alternative to restore the physiological kinematics of the operated disc. Few studies directly compare ADR and CS construct for their efficacy. METHODS: Patients who received single-level ADR or CS between January 2008 and December 2018 were included. Data collected was preoperatively, intraoperatively, and postoperatively (6, 12, 24 months). Demographic information, surgical information, complications, follow-up surgery, and outcome ratings (Japanese Orthopaedic Association [JOA], Neck Disability Index [NDI], Visual Analog Scale [VAS] neck and arm, 36-item Short Form Health Survey [SF-36], EuroQoL-5 Dimension [EQ-5D]) were gathered. The radiological assessment included motion segment height, adjacent disc height, lordosis, cervical lordosis, T1 slope, the sagittal vertical axis C2–7, and adjacent level ossification development (ALOD). RESULTS: Fifty-eight patients were included (ADR: 37 and CS: 21). At 6 months, both groups’ JOA, VAS, NDI, SF-36, and EQ-5D scores significantly improved, and the positive trends persisted at 2 years. Noted no significant difference in the enhancement of clinical scores except for the VAS arm (ADR: 5.95 vs. CS: 3.43, p=0.001). Radiological parameters were comparable except for the progression of ALOD of the subjacent disc (ADR: 29.7% vs. CS: 66.9%, p=0.02). No significant difference in adverse events or severe complications seen. CONCLUSIONS: ADR and CS obtain good clinical results for symptomatic single-level cervical DDD. ADR demonstrated a significant advantage over CS in the improvement of VAS arm and reduced progression of ALOD of the adjacent lower disc. No statistically significant difference of dysphonia or dysphagia between the two groups were seen, attributed to their comparable zero profile.