Subsidence Ratio after Anterior Cervical Interbody Fusion Using an Intraoperative Custom-made Cervical Cage

Objective : The postoperative subsidence of anterior cervical interbody fusion for cervical degenerative diseases gives rise to segmental kyphotic collapse, screw loosening, and chronic neck pain. So, intraoperative custom-made polymethylmethacrylate [PMMA] C-cage has been developed to prevent subsidence following anterior cervical fusion. Methods : A total of patients who underwent anterior cervical interbody fusion with a intraoperative custom - made cervical cage filled with local bone and demineralized bone matrix [group A] were analyzed prospectively from June 2004 to June 2005. These were compared with 40 patients who were treated with iliac bone graft [group B]. We evaluated subsidence ratio, change of segmental angle, distraction length and segmental angle. Statistical analysis was performed using independent sample t-test and Pearson correlation coefficient. Results : Group A had a statistically significant decrease in subsidence ratio [$0.64{\pm}0.43%$, p=0.00]. distraction length [$2.42{\pm}1.25\;mm$, p=0.02], and follow angle change [$1.78{\pm}1.69^{\circ}$, p=0.01] as compared with Group B. However, there was no statistically significant difference in postoperative segmental angle change [p=0.66]. On the analysis of the correlation coefficient, the parameters showed no interrelationships in the group A. On the other hand, subsidence ratio was affected by distraction length in the group B [Pearson correlation=0.448]. Conclusion : This operative technique would be contributed for the reduction of a postoperative subsidence after the anterior cervical interbody fusion procedure for cervical disc disease with moderate to severe osteoporotic condition and segmental loss of lordosis.