Biomechanical stability of a bioabsorbable self-retaining polylactic acid/nano-sized β-tricalcium phosphate cervical spine interbody fusion device in single-level anterior cervical discectomy and fusion sheep models

Lu Cao,¹ Ping-Guo Duan,¹ Xi-Lei Li,¹ Feng-Lai Yuan,³ Ming-Dong Zhao,² Wu Che,¹ Hui-Ren Wang,¹ Jian Dong<sup>1

1</sup>Department of Orthopedic Surgery, Zhongshan Hospital, State Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai, China; ²Department of Orthopedic Surgery, Jinshan Hospital, Fudan University, Shanghai, China; ³Affiliated Third Hospital of Nantong University, Wuxi, China

Purpose: The aim of this study was to investigate the biomechanical stability provided by a novel, polylactic acid/nano-sized, β-tricalcium phosphate, bioabsorbable, self-retaining cervical fusion cage (BCFC).
Methods: Quasistatic nonconstraining torques (maximum 1.5 NM) induced flexion, extension, lateral bending (±1.5 NM), and axial rotation (±1.5 NM) on 32 sheep cervical spines (C2–C5). The motion segment C3–C4 was first tested intact; the following groups were tested after complete discectomy: autologous tricortical iliac crest bone graft, Medtronic–Wego polyetheretherketone (PEEK) cage, Solis PEEK cage, and BCFC. The autologous bone graft group was tested with an anterior plate. The mean range of motion (ROM) was calculated from the load-displacement curves.
Results: BCFC significantly decreased ROM in lateral bending and axial rotation compared to other implants, and no significant difference in ROM between two types of PEEK cages and BCFC could be observed in flexion and extension. Anterior cervical plate (ACP) significantly decreased ROM in flexion and extension, but no significant difference in ROM between BCFC and bone graft plus ACP could be determined in lateral bending and axial rotation.
Conclusion: The BCFC device showed better stability to autologous tricortical iliac crest bone graft and PEEK cages in single-level anterior cervical discectomy and fusion models and thus may be a potential alternative to the current PEEK cages.

Keywords: biomechanics, cervical spine, cages, bioabsorbable, sheep