Sagittal alignment analysis on using self-locking stand-alone cages in two-level anterior cervical discectomy and fusion

English Keywords:Cevical spondylosis  Anterior cervical discectomy and fusion  Self-locking stand-alone cages  Sagittal alignments

English Abstract:

  【Abstract】 Objectives: To investigate changes of sagittal alignments of using self-locking stand-alone cages in anterior cervical discectomy and fusion(ACDF). Methods: A retrospect research from January 2012 to June 2014 was performed, 160 two-level cervical spondylosis patients undergoing ACDF were enrolled and divided into uni-anchored group(UAG) and bi-anchored group(BAG) according to the anchor type of self-locking stand-alone cage (MC+ and ROI-C). Cervical standing radiographs were taken at pre-operation, 3 days after operation, 3 months after operation and the last follow-up. The sagittal parameters were measured, including height of operation segment(HOS), angle of operation segment(AOS), C2-C7 angle, C2-C7 sagittal vertical axis(C2-C7 SVA) and T1 slope(T1S). Erk method was used to evaluate the fusion status of operation segment. Statistic methods, including independent t-test and paired t-test, were performed to determine the significance of difference between UAG and BAG. Correlation among the radiographic parameters of 160 patients at every check point were sought by Pearson correlation analysis. In addition, the fusion rank of two groups was compared by Mann-Whitney U test and Wilcoxon signed rank test. Results: All cases obtained the follow-up with an average of 13.42±6.01 months(range, 6 to 31 months). At pre-operation, 3 days after operation, 3 months after operation and the last follow-up, positive correlations were presented between AOS and C2-C7 angle, C2-C7 angle and T1S, AOS and T1S, T1S and C2-C7 SVA（P<0.01）. No significant difference was found between C2-C7 SVA and AOS, C2-C7 SVA and C2-C7 angle（P>0.01）. In both groups, HOS, AOS, C2-C7 angle and T1S increased after operation(P<0.05). AOS, C2-C7 angle and T1S of UAG showed a statistic lower value than BAG at 3 months after operation and the last follow-up（P<0.05）. The fusion status of both groups had no significant difference at 3 months after operation and the last follow-up(P>0.05). The fusion rank at the last follow-up was significant lower than that at 3 months after operation(P<0.05). Conclusions: The height and angle of operation segment and cervical curve can be corrected after ACDF by using both self-locking stand-alone cages. ROI-C cage can be considered as a better choice in maintaining AOS and cervical lordosis compared to MC+ cage. The thoracic radiographic sagittal parameters may be altered after ACDF following the loss of cervical curve.