Fixed-Angle Static Versus Variable-Angle Dynamic Plates for Multilevel Anterior Cervical Discectomy and Fusion.

STUDY

DESIGN

Retrospective cohort study.

OBJECTIVE

This study compared multilevel ACDF using fixed-angle static versus dynamic plates. We hypothesized that static plates would better maintain lordosis and fusion construct height, with similar functional outcomes and nonunion rates, compared with dynamic plates.

SUMMARY OF BACKGROUND DATA: Dynamic plates allow for translational collapse, theoretically improving fusion rates; conversely, fixed-angle static plates limit toggle at the screw-plate interface and may better maintain lordosis and construct height. Existing research comparing traditional static plates to dynamic plates has yielded variable results regarding nonunion rates, outcomes, and radiographic parameters.

METHODS

This retrospective cohort study included patients who underwent 2- or 3-level ACDF for degenerative pathology by a single orthopedic surgeon at an academic medical center between April 2017 and July 2022. The plate type was switched from dynamic to fixed-angle static on January 1, 2020. Outcomes included fusion construct lordosis and height loss, per-segment height loss, PROMIS physical function, VAS neck and arm, and nonunion. Nonunion was determined using lateral flexion/extension x-rays and was defined as >2 mm of movement between adjacent spinous processes of the construct. Height loss and lordosis were compared postoperatively using upright lateral x-rays with those at the last clinic visit.

RESULTS

There were 40 patients in the dynamic group and 41 patients in the static group. The dynamic group had a longer time to last radiographic follow-up (P=0.013). At final follow-up, fusion construct height loss (P=0.538) and per-fused segment height loss (P=0.443) were similar across groups, but fusion construct lordosis was significantly greater in the static group (P=0.015). Nonunion rates (P=0.467), 1-year postoperative VAS neck (P=0.806), VAS arm (P=0.369), and PROMIS PF scores (P=0.704), and complication rates were similar across groups.

CONCLUSION

At short-term follow-up, fixed-angle static plates may better maintain lordotic alignment with similar outcome scores, union rates, and complication rates compared with dynamic plates.