Long cervical fusions: are multiple segmental plates less likely to fail than a single long plate?

BACKGROUND

Anterior cervical discectomy and fusion (ACDF) is widely performed for cervical pathology, yet multilevel anterior constructs are associated with higher rates of dysphagia, pseudoarthrosis, and mechanical failure-particularly at the caudal segment. These complications may arise from stress concentration and load transfer through long anterior cervical plates. Segmentally separated fixation, utilizing multiple short plates rather than a single long plate, may reduce these risks by limiting exposure, shortening operative time, and distributing mechanical loads more evenly. The purpose of this study was to compare the biomechanical behavior of multilevel ACDF constructs stabilized with multiple segmental plates versus a single long plate.

METHODS

Twelve fresh-frozen human cadaveric cervical spines (C4-C7) underwent ACDF using either a single long plate or multiple segmental plates. Bone quality was quantified via C7 trabecular Hounsfield units on computed tomography (CT), and specimens were randomized by density. Identical constructs were also tested in polyurethane foam cervical models to minimize biological variability. Specimens were mounted to multiaxial test platforms and subjected to fatigue cycling under flexion-extension, lateral bending, and axial rotation. Construct stiffness was recorded at baseline and after 1,500 cycles in each motion plane. Stiffness loss was analyzed with one-way analysis of variance (ANOVA) and normalized to bone density.

RESULTS

Initial construct stiffness did not differ between groups (P=0.86). After cyclic loading, multiple segmental plates demonstrated significantly greater stiffness retention in axial rotation (51%±10% vs. 88%±4% loss; P<0.001) in synthetic models. No significant differences were found for flexion-extension or lateral bending. In cadaveric specimens, normalized stiffness loss was comparable between groups, likely reflecting greater biological variability.

CONCLUSIONS

Segmentally separated anterior fixation for multilevel ACDF preserves rotational stiffness at the caudal segment more effectively than long single-plate constructs in controlled models. This suggests a potential mechanical advantage that may translate to reduced stress concentration and lower failure risk in multilevel anterior cervical reconstructions. Further in-vivo and clinical correlation studies are warranted to validate these biomechanical findings and assess long-term fusion outcomes.