Axial vs. angular dynamization of anterior cervical fusion implants.

Aim of our study was to compare anterior cervical fusion with fusion augmented with dynamic implants and with the first generation-plate. Methods. Patients with radiculopathy and/or myelopathy were included in a prospective cohort study. Clinical outcome was assessed according to the Nurick, Odom, and SF 36 scales. Rotation and translation of screws, and quality of fusion (Tribus) were assessed at the 6-week and 4-year follow-up examinations. Neurodecompression was performed in 81 patients (one-level N = 45, two-level N = 26 and multi-level N = 10) in the period from January 2001 to September 2003. 50 male and 31 female patients were divided into three groups, depending upon type of fusion: 1. Augmented with dynamic implants (N = 33), 2. Augmented with H-plate (N = 33), and 3. Non-augmented (N = 15), one-level. There were no significant differences in clinical outcomes between the groups. Dynamization was detected in both augmented groups: axial in the dynamic implant group (mean translation +/- SD = 2.67 +/- 0.79 mm), and angular in the H-plate group (angle of rotation 7.2 degrees +/- 3.04 degrees). Six-week fusion was significantly better in the dynamic implants and non-augmented groups, as compared with the H-plate group. Two patients in the H-plate group developed pseudoarthrosis, 7 patients in the dynamic implant group had supradjacent segment heterotopic ossification and two of these additional ankylosis. Three patients in the non-augmented group had dislodgement of the bone graft with transient dysphagia in one of them. Our results suggest that selection of implants is not crucial for clinical outcome. Subsidence is allowed with both fixation systems. Fusion is faster and more effective in the axially dynamized group.