Risk Factors for Cervical Sagittal Malalignment after Cervical Laminoplasty

Abstract

Objective: Objective: To investigate the risk factors for cervical sagittal malalignment after cervical laminoplasty. Methods: The study included 41 patients who were treated with cervical lamino- plasty from February 2006 to January 2010. The average follow-up period was 30.5 (range, 23-59 months). We divided the enrolled patients into three groups (Group A: C2 and C7 ligament preser- vation, Group B: C2 or C7 ligament preservation, Group C: Both C2 and C7 ligament excised). The patients’ preoperative and postoperative clinical results were retrospectively reviewed using the Japanese Orthopedic Association (JOA) score for functional outcome. Radiography was performed before surgery and at the final follow-up, and the C2-7 Cobb angle, sagittal vertical axis (SVA) C2-7, range of motion (ROM), C2 tilt, C1-2 lordosis, and T1 tilt were measured to evaluate cervical align- ment. Results: Change in SVA C2-7, C2-7 lordosis, C1-2 lordosis, C2 tilt, and ROM showed statisti- cally significant differences in groups B and C, but no statistically significant difference in group A for all these radiographic parameters. There was no statistically significant difference between preoperative and postoperative clinical outcome measurements for each group, as assessed by JOA scores (p=0.999, 0.095, and 0.111, respectively). In ANOVA, change in SVA C2-7 showed a statisti- cally significant difference (p=0.037) between the groups. The post-hoc analysis revealed a statisti- cally significant difference between groups A and B (p=0.044) and between groups A and C (p= 0.011). Conclusion: We investigated SVA C2-7 as a factor of cervical sagittal alignment, and found that as the involvement of C2 and C7 ligamentous structures increased, SVA C2-7 also increased.