Publisher: Elsevier Country of Publication: United States NLM ID: 1250250 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1879-0534 (Electronic) Linking ISSN: 00104825 NLM ISO Abbreviation: Comput Biol Med Subsets: MEDLINE

Finite Element Analysis* , Spinal Fusion*/instrumentation , Spinal Fusion*/methods , Cervical Vertebrae*/surgery , Cervical Vertebrae*/physiopathology , Diskectomy*/instrumentation , Diskectomy*/methods , Prostheses and Implants* , Models, Biological*, Humans ; Biomechanical Phenomena ; Range of Motion, Articular ; Stress, Mechanical ; Male

Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Anterior cervical discectomy and fusion (ACDF) is an established surgical method for restoring neurological function and reconstructing cervical curvature. However, a limited number of studies have investigated the biomechanical changes after ACDF involving multiple surgical segments. Therefore, this study aimed to investigate the effect of surgical devices, number of surgical segments and motions on the strain and stress distribution of the implants. A validated finite element cervical spine model (C2-C7) was used to develop four postoperative models involving zero-profile (ZP) devices or cage and plate (CP) constructs across two- and three-segment ACDF. We analyzed postoperative range of motion (ROM) and implant strain-stress characteristics. ZP devices yielded higher ROM values on fused segments compared to CP devices. The ZP group exhibited higher maximum strain values and predicted effective strain area (Pesa) on bone graft surfaces compared to the CP group. Similarly, maximum and average stress values were greater in the ZP group, with minimal influence from the number of surgical segments on strain and stress distributions. Two-way ANOVA showed that the type of surgical device significantly affected stress values across multiple moment sizes during extension and flexion, while the number of surgical segments was significant only under specific conditions, such as extension at 1.0 Nm and 1.5 Nm and flexion at 1.5 Nm. Our study found that increasing the number of surgical segments had little impact on implant biomechanics. ZP devices significantly increased strain and stress values on bone grafts, with higher stress and larger Pesa area at the graft-endplate interface, promoting bone growth in fused segments. In contrast, CP devices showed lower stress and strain values, warranting caution in multi-segment surgeries.
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