Staff Physician Scripps Health La Jolla, California, United States
Introduction: Multilevel ACDF constructs with a single contiguous plate have higher rates of pseudoarthrosis, dysphagia and mechanical failure, compared to single level fusions. The use of low-profile single segment plates in series has been proposed as a means of making anterior fixation more facile, while avoiding the biomechanical limitations of “zero profile” integrated fixation implants.
Methods: We prospectively followed patients undergoing multilevel segmental ACDF from 2018-2021. Pre and post operative demographic/radiographic characteristics and PROMs were recorded. Fusion was assessed through evaluation of bridging bone and interspinous movement (ISM, < 2mm) on flexion/extension x-rays
Results: 66 patients with one-year follow up were included in the analysis. NDI scores improved from an average of 33.9 (17.9) preop to 17.7 (13.0) at 1 year (p < 0.001), and VAS neck pain improved from 5.3 (3.0) to 2.2 (2.1) (p < 0.001). Segmental lordosis at instrumented levels (N=145) increased an average of 4.1º (5.7) from preop to postop (p < 0.001) and reduced by 2.1º (4.2) from postop to 1yr (p < 0.001). The overall rate of fusion at one year was 98.7% by bony bridging and 77.6% by ISM ( < 2mm). There were no alignment measures (pre- to post-op or postop to 1yr) that predicted fusion rates with significance. Of note, no differences in fusion rates were observed based on number of levels fused (2 to 4 levels, p>0.16). Four (6.1%) patients experienced a complication; 3 (4.5%) C5 palsy, 1(1.5%) hematoma. Importantly, no patients required reoperation for pseudoarthrosis or instrumentation failure.
Conclusion : Multilevel segmental ACDF is safe and led to significant improvements in NDI, pain, and radiographic alignment in this cohort. There was an excellent rate of fusion based on bone bridging, but a greater than expected amount interspinous movement (22.4%, >2mm) was observed in asymptomatic patients, suggesting further study may be needed to assess fusion grading in multilevel segmental ACDF. Unlike traditional ACDF, the number of levels treated did not appear to influence rates of pseudoarthrosis in segmental ACDF. Further research is needed to evaluate the potential long-term benefit of segmental plating on adjacent segment degeneration.
