A Novel Semi-Cannulated Screw with Cement Augmentation for Revision Lateral Mass Fixation: A Cyclic Loading Biomechanical Study

Abstract

Dongbin Qu, Division of Spine Surgery, Department of Orthopaedics, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510000, P. R. China. Email: nfyy_qu@126.com Canyang Huang, Division of Spine Surgery, Department of Orthopaedics, Quanzhou First Hospital Affiliated to Fujian Medical University, Quanzhou, Fujian 362000, P. R. China. Email: huangcy0595@sina.com Purpose: This study biomechanically compared a novel semi-cannulated lateral mass screw with cement augmentation against conventional solid screws for stabilizing loosened cervical lateral masses under cyclic loading.

Methods: Eight fresh human cervical specimens underwent μCT scanning for BMD assessment. Each specimen received both screw types: on the augmentation side, semi-cannulated screws were initially loosened via pull-out testing then reinserted with cement; on the (contralateral) primary side, conventional solid screws were placed Awithout augmentation. After cyclic loading, vertical displacement, toggling angle, and rotation center distance (ORC) at the screw-bone interface were measured, followed by final pull-out force tests.

Results: The mean BMD of the lateral masses was 305.05 ± 48.33 mg/cm³. Following cyclic loading, the augmentation side exhibited a significantly higher pull-out force than its initial state (P < 0.01), though not statistically greater than the primary side. Under cyclic loading, the augmentation side demonstrated significantly superior stability: vertical displacement increased by only 6.25%, compared to a 70.69% increase on the primary side (P < 0.05). The toggling angle decreased by 2.36% on the augmentation side, versus a significant 79.92% increase on the primary side (P < 0.05). The ORC increased by 2.13% on the augmentation side, markedly lower than the 38.03% increase on the primary side.

Conclusion: The novel semi-cannulated lateral mass screw with cement augmentation demonstrated superior dynamic stability and significantly improved fixation strength after cyclic loading compared to conventional solid screws, offering a promising revision strategy for cervical spines with screw loosening or osteoporosis.