Change of cervical balance following single to multi-level interbody fusion with cage

Postoperative limitation of cervical movement and adjacent disc degeneration are major causes of postoperative neck pain after anterior cervical discectomy and interbody fusion (ACDF). We present a retrospective study of dynamic radiographic change following ACDF with cages. We performed ACDF in 50 patients with cervical degenerative diseases, divided into three groups based on the level of interbody fusion (Group A: one-level; Group B: two-level; Group C: three-level). Preoperative and postoperative flexion-extension X-rays were acquired and cervical range of motion (ROM), lordosis, fusion rate, cage subsidence rate, postoperative neck pain as evaluated by visual analogue scale (VAS) and upper adjacent level segmental movement were evaluated. The average following time was 14.6 months. The mean change in lordotic curve was -2.31 +/- 9.53 degrees for Group A, 5.60 +/- 6.96 degrees for Group B, and 3.23 +/- 7.50 degrees for Group C (p value = 0.03). The mean change in flexion angle was -5.46 +/- 8.69 degrees for Group A, -10.2 +/- 7.38 degrees for Group B, and -13.86 +/- 10.33 degrees for Group C (p value = 0.039). The mean change in total cervical ROM was -3.85 +/- 18.74 degrees for Group A, -12.73 +/- 10.31 degrees for Group B, and -16.95 +/- 10.57 degrees for Group C (p value = 0.02). Follow-up cervical MRI for patients with persistent neck pain showed no evidence of adjacent level degeneration. There were no significant differences between the three groups with respect to postoperative change in cervical extension angle, upper adjacent level segmental movement, neck pain VAS, fusion rate or cage subsidence rate. The further decrease in total cervical ROM and flexion movement after multi-level ACDF was observed. However, a more long-term follow-up was needed to assess the actual aetiologies of upper adjacent level degeneration.