Comparison of Curvature Between the Zero-P Spacer and Traditional Cage and Plate After 3-Level Anterior Cervical Discectomy and Fusion Mid-term Results

Study Design: A retrospective study. Objective: To compare clinical and radiologic outcomes of 3-level anterior cervical discectomy and fusion between a zero-profile (Zero-P) spacer and a traditional plate in cases of symptomatic cervical spine spondylosis. Summary of Background Data: Anterior cervical decompression and fusion is indicated for patients with anterior compression or stenosis of the spinal cord. The Zero-P spacers have been used for anterior cervical interbody fusion of 1 or 2 segments. However, there is a paucity of published clinical data regarding the exact impact of the device on cervical curvature of 3-level fixation. Methods: Clinical and radiologic data of 71 patients undergoing 3-level anterior cervical discectomy and fusion from January 2010 to January 2012 were collected. Zero-P spacer was implanted in 33 patients, and in 38 cases stabilization was accomplished using an anterior cervical plate and intervertebral cage. Patients were followed for a mean of 30.8 months (range, 24-36 mo) after surgery. Fusion rates, changes in cervical lordosis, and degeneration of adjacent segments were analyzed. Dysphagia was assessed using the Bazaz score, and clinical outcomes were analyzed using the Neck Disability Index and Japanese Orthopedic Association scoring system. Results: Neurological outcomes did not differ significantly between groups. Significantly less dysphagia was seen at 2-and 6month follow-up in patients with the Zero-P implant (P < 0.05); however, there was significant less cervical lordosis and the lordosis across the fusion in patients with the Zero-P implant (both P < 0.05). Degenerative changes in the adjacent segments occurred in 4 patients in the Zero-P group and 6 patients in the standard-plate group (P = 0.742); however, no revision surgery was done. Conclusions: Clinical results for the Zero-P spacer were satisfactory. The device is superior to the traditional plate in preventing postoperative dysphagia; however, it is inferior at restoring cervical lordosis. It may not provide better sagittal cervical alignment reconstruction in 3-level fixation. Prospective randomized trials with more patients and longer follow-up periods are required to confirm these observations.