Follow-up Comparison of Two Different Types of Anterior Thoracolumbar Instrumentations in Trauma Cases : Z-plate vs. Kaneda Device

Objective : In a variety of thoracolumbar diseases, corpectomy followed by interbody bone graft and anterior instrumentation has allowed direct neural decompression and reconstruction of the weight-bearing column by short segments fusion. In this study, we compared spinal stability of the two different anterior thoracolumbar instruments : Z-plate and Kaneda device representing plate and two-rods type, respectively. Methods : A retrospective review was performed for all the patients with thoracolumbar diseases or traumas treated with anterior corpectomy, autologous iliac bone graft, and fixation with instruments from 1996 to 2000. For the anterior instrumentation, Z-plate or Kaneda device was used for 24 (M:F=5:9, average age=37) and 12 (M:F=9:3, average age=41) patients, respectively. The plain AP and lateral flexion-extension films were taken immediately after surgery and at each follow-up. The sagittal and coronal Cobb’s angles at the operation segments were used to observe the change of initial fixation status. The surgical time length and bleeding amount of the two groups were compared. Intra-operative and post-operative instrumentassociated complications were evaluated. Student t-test was used for statistical analysis and p-value less than 0.05 was considered to be significant. Results : Mean follow-up durations for Z-plate and Kaneda device were 24 and 21 months, respectively. The fusion rate was 91% for Z-plate and 100% for Kaneda device. Two cases of Z-plate group showed instrumentation failure during the followup period, in which additional surgery was necessary. The mean differences of sagittal Cobb’s angles among the AP images immediate after surgery and at follow-up were 7 and 2 degrees for Z-plate and Kaneda device, respectively (p<0.05). The mean differences of coronal Cobb’s angles were 5 and 2 degrees for Z-plate and Kaneda device, respectively (p<0.05). No intra-operative complication has occurred in both groups. There was no difference in surgery time and bleeding amount between two groups. Conclusion : We think that Kaneda device (rod type) is stronger than Z-plate (plate type) to keep the spinal stability after anterior thoracolumbar surgery.