Radiographic Analysis of Cervical and Spinal Alignment in Multilevel ACDF with Lordotic Interbody Device.

BACKGROUND: Restoration and maintenance of cervical lordosis is an important clinical parameter in spine surgery. The purpose of this study was to determine the extent to which a multilevel anterior cervical discectomy and fusion (ACDF: greater than 3 levels) procedure restores cervical lordosis and the affect of increasing lordosis on sagittal vertical axis.

METHODS: We performed a retrospective radiographic analysis of 69 patients who underwent multilevel ACDF by 2 surgeons between 2013 and 2014. We measured the global and segmental sagittal alignment of the cervical spine using the cobb method at 4 time intervals (preop, post op 4wks, 10wks and 6 months) as well as the sagittal vertical axis (SVA) using both a C1-S1 and C7-S1 plumb line methods at 2 time intervals (preop and post op 4wks). Radiographs were measured by three reviewers.

RESULTS: Interrater reliability was good to excellent for all measurements. Cervical lordosis significantly increased from preop 10.26° to 4 weeks postop 19.44° and was maintained up to 6 months 19.34 (p<0.0005). Segmental cervical lordosis was also significantly increased from preop 8.22° to post op at 4 weeks (20.26°) and was maintained at post op 10weeks 20.30° and post op 6 months 19.56° (p<0.0005). C7-S1 SVA and C1-S1 SVA also significantly increased from 12.04mm preop to 27.49mm post op 4 wks (p<0.0005) and -1.93mm preop to 8.67mm post op (p<0.0005) respectively. A change in C2-C7 lordosis positively correlated with a change in C7-SVA and C1-SVA (r=0.37, P<0.005, and r=0.312, p<0.05 respectively).

CONCLUSIONS: Multilevel ACDF significantly increases and maintains both segmental and global cervical lordosis up to 6 months after surgery. Increasing C2-C7 global lordosis is correlated with increasing positive sagittal vertical axis. Level of evidence: IV.