Anterior cervical interbody fusion with the Zero-P spacer: mid-term results of two-level fusion.

PURPOSE: Our aim was to compare the safety and efficacy of anterior cervical discectomy and fusion (ACDF) using the Zero-P spacer versus the plate method in patients with cervical spine spondylosis. METHODS: Clinical and radiologic data from 69 patients undergoing two-level ACDF from January 2009 to May 2011 were collected prospectively. The Zero-P spacer was implanted in 37 patients (group A) and the anterior cervical plate and interbody cage in 32 (group B). Patients were followed for at least 3 years after surgery. Clinical outcomes were analyzed using the Neck Disability Index and Japanese Orthopaedic Association (JOA) scoring. The thickness of the prevertebral soft tissue at the fused levels was measured on the lateral cervical spine radiographs and dysphagia was assessed using the Bazaz score. Fusion rate, change in cervical lordosis, and adjacent segment degeneration were analyzed. RESULTS: Neurologic outcomes were statistically equivalent between the two groups. The incidence of postoperative dysphagia was significantly lower in group A than in group B at 2 and 6 months (p < 0.05). At the final follow-up, there were no significant differences in the C2-C7 Cobb angles between the two groups (p > 0.05). Also, degenerative changes in adjacent segments occurred in five group A patients and seven group B patients (p = 0.361). There were no differences in fusion rate during the radiologic follow-up. CONCLUSIONS: Clinical results with the Zero-P spacer used for two-level ACDF were satisfactory. The device is superior to the traditional plate for preventing postoperative dysphagia and avoiding possible complications associated with a plate. Prospective trials with more patients and longer follow-ups are required to confirm these observations.