Biomechanical Testing that Compares Four Anterior Cervical Fixation Models with the Effect of Posterior Fixation Augmentation

Anterior cervical discectomy and fusion (ACDF) and cervical vertebrectomy with interbody fusion (CVIF) are commonly performed spine procedures that rely on anterior plate fixation for stability. This biomechanical study evaluated the effects of screw length, plate length, and posterior fixation augmentation on the stability of anterior cervical fixation constructs under worst-case conditions. Using osteopenic-grade polyurethane foam blocks, four construct configurations representing discectomy and corpectomy models were tested with varying anterior plate lengths (22 mm, 34 mm), screw lengths (14 mm, 16 mm), and the addition of posterior fixation. Static and fatigue testing were per-formed using methods adapted from ASTM F1717, with fatigue run-out defined at 1.2 million cycles to simulate the fusion period. Static testing demonstrated the lowest yield load in constructs using a short plate with shorter screws. Fatigue testing showed that increasing screw length from 14 to 16 mm increased maximum fatigue load by 1.6-fold, while the addition of posterior fixation increased fatigue capacity by 3.6-fold. Increasing plate length resulted in a modest reduction in fatigue performance. These findings indicate that posterior fixation provides the greatest improvement in construct fatigue resistance, while increased screw length offers a less invasive means of enhancing stability, informing surgical strategies for high-risk ACDF and CVIF cases.