Biomechanical Analysis of an Anterior Cervical Discectomy and Fusion Pseudarthrosis Model Revised With Machined Interfacet Allograft Spacers

Abstract

Study Design: Biomechanics study. Objectives: To evaluate the biomechanical advantage of interfacet allograft spacers in an unstable single-level and 2-level anterior cervical discectomy and fusion (ACDF) pseudoarthrosis model. Methods: Nine single-level and 8 two-level ACDF constructs were tested. Range of motion in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) at 1.5 N m were collected in 4 testing configurations: (1) intact spine, (2) ACDF with interbody graft and plate/screw, (3) ACDF with interbody graft and plate/loosened screws (loose condition), and (4) ACDF with interbody graft and plate/loosened screws supplemented with interfacet allograft spacers (rescue condition). Results: All fixation configurations resulted in statistically significant decreases in range of motion in all bending planes compared with the intact spine ( P < .05). One Level. Performing ACDF with interbody graft and plate on the intact spine reduced FE, LB, and AR 60.0%, 64.9%, and 72.9%, respectively. Loosening the ACDF screws decreased these reductions to 40.9%, 44.6%, and 52.1%. The addition of interfacet allograft spacers to the loose condition increased these reductions to 74.0%, 84.1%, and 82.1%. Two Level. Performing ACDF with interbody graft and plate on the intact spine reduced FE, LB, and AR 72.0%, 71.1%, and 71.2%, respectively. Loosening the ACDF screws decreased these reductions to 55.4%, 55.3%, and 51.3%. The addition of interfacet allograft spacers to the loose condition significantly increased these reductions to 82.6%, 91.2%, and 89.3% ( P < .05). Conclusions: Supplementation of a loose ACDF construct (pseudarthrosis model) with interfacet allograft spacers significantly increases stability and has potential applications in treating cervical pseudarthrosis.

Multilevel, Percutaneous Posterior Cervical Interfacet Distraction and Fusion for Cervical Spondylotic Radiculopathy

“…Kasliwal et al 30 studied symptomatic pseudoarthrosis treated with PCIDF and found high fusion rates and good clinical outcomes. Biomechanical studies have also suggested that PCIDF can augment anterior procedures to improve arthrodesis by increasing stability and limiting cervical segmental motion 31–34 . Kramer et al 21 confirmed this clinically and found that PCIDF was effective in obtaining multilevel circumferential fusion in patients deemed to be at high-risk in developing pseudoarthrosis.…”

The influence of over-distraction on biomechanical response of cervical spine post anterior interbody fusion: a comprehensive finite element study

“…Some surgeons prefer over-distraction and implanting the interbody cages with larger height size. Currently, a universally accepted consensus or standardized definition regarding the specific threshold for distraction displacement that categorizes cervical spine surgery as either “over-distraction” or “normal distraction” in the context of ACDF does not exist ( Kirzner et al, 2018 ; Hah et al, 2020 ; Lawless et al, 2022 ). The classification of over-distraction largely depends on individual surgeons, specific medical institutions, and the relevant clinical guidelines they follow, which are influenced by their collective experience.…”

“…Despite significant advancements in interbody cage materials and structural designs over the past two decades, surgeons continue to face challenges in selecting the appropriate size for interbody cages ( Kwon et al, 2005 ; Chong et al, 2015 ). The task of determining the correct size remains intricate and requires careful consideration of individual patient factors and specific surgical requirements ( Hah et al, 2020 ; Lawless et al, 2022 ). Despite the progress in cage technology, ensuring the optimal fit and function of the interbody cage remains a critical aspect of successful surgical outcomes for patients.…”

“…In ACDF procedures, the process of distraction holds immense significance as it facilitates the separation of vertebral bodies, leading to neural structure decompression and supporting fusion ( Kirzner et al, 2018 ; Lawless et al, 2022 ). Surgeons aim to achieve an optimal intervertebral height to ensure effective fusion and decompression ( Hah et al, 2020 ). However, determining the precise threshold for what qualifies as “over-distraction” can vary substantially due to a multitude of factors.…”

Biomaterials for Interbody Fusion in Bone Tissue Engineering

“…Walsh et al designed an interbody fusion cage (measuring 4.5 mm high, 10 mm wide, and 20 mm long) with a central hole for transplant material injection, which was printed to fit the L4–L5 intervertebral space of sheep, providing support for clinical implantation ( Walsh et al, 2018 ). The design of the fixed device cannot be ignored, and the nailboard system is the most commonly used method applied to fixation ( Hah et al, 2020 ). Fixed device is generally used to maintain the stability of the intervertebral space for a better fusion effect ( Caplan et al, 2020 ).…”