Biomechanics of intervertebral cervical fusion cages

Background: The cervical anterior transpedicular screw (ATPS) fixation technology can provide adequate stability for cervical three-column injuries. However, its high risk of screw insertion and technical complexity have restricted its widespread clinical application. As an improvement over the ATPS technology, the cervical anterior transpedicular root screw (ATPRS) technology has been introduced to reduce the risk associated with screw insertion. This study aims to use finite element analysis (FEA) to investigate the biomechanical characteristics of a cervical spine model after using the novel ATPRS intervertebral fusion system, providing insights into its application and potential refinement...

BACKGROUND: Intervertebral cages used in clinical applications were often general products with standard specifications, which were challenging to match with the cervical vertebra and prone to cause stress shielding and subsidence. OBJECTIVE: To design and fabricate customized tantalum (Ta) intervertebral fusion cages that meets the biomechanical requirements of the cervical segment. METHODS: The lattice intervertebral cages were customized designed and fabricated by the selective laser melting...

BACKGROUND: Porous cages are considered a promising alternative to high-density cages because their interconnectivity favours bony ingrowth and appropriate stiffness tuning reduces stress shielding and the risk of cage subsidence. METHODS: This study proposes three approaches that combine macroscopic topology optimization and micropore design to establish three new types of porous cages by integrating lattices (gyroid, Schwarz, body-centred cubic) with the optimized cage frame...

OBJECTIVES: The three-dimensional printing titanium (3DPT) cage with excellent biomechanical properties and osseointegration capabilities has been initially used in spinal fusion, while the polyetheretherketone (PEEK) cage, a bioinert material device, has been a widely used for decades with relatively excellent clinical outcomes. This study was performed to investigate the early radiographic and clinical outcomes of 3DPT cage versus PEEK cage in patients undergoing anterior cervical discectomy and fusion (ACDF) and transforaminal lumbar interbody fusion (TLIF)...

Introduction: Anterior cervical discectomy and fusion (ACDF) has been considered as the gold standard surgical treatment for cervical degenerative pathologies. Some surgeons tend to use larger-sized interbody cages during ACDF to restore the index intervertebral disc height, hence, this study evaluated the effect of larger-sized interbody cages on the cervical spine with ACDF under both static and cyclic loading. Method: Twenty pre-operative personalized poro-hyperelastic finite element (FE) models were developed...

STUDY DESIGN: Retrospective cohort study. PURPOSE: To characterize the postoperative outcomes and economic costs of anterior cervical discectomy and fusion (ACDF) procedures using synthetic biomechanical intervertebral cage (BC) and structural allograft (SA) implants. OVERVIEW OF LITERATURE: ACDF is a common spine procedure that typically uses an SA or BC for the cervical fusion. Previous studies that compared the outcomes between the two implants were limited by small sample sizes, short-term postoperative outcomes, and procedures with single-level fusion...

BACKGROUND: Intermediate vertebral collapse is a newly discovered complication of consecutive two-level anterior cervical discectomy and fusion (ACDF). There have been no analytical studies related to the effects of endplate defects on the biomechanics of the intermediate vertebral bone after ACDF. This study aimed to compare the effects of endplate defects on the intermediate vertebral bone biomechanics in the zero-profile (ZP) and cage-and-plate (CP) methods of consecutive 2-level ACDF and to determine whether collapse of the intermediate vertebra is more likely to occur using ZP...

Anterior Cervical Discectomy and Fusion (ACDF) is the most popular and effective procedure for patients with intervertebral disc degeneration, where the degenerated disc is replaced with an interbody implant (widely known as cage). The design of the cage plays a vital role since it has to provide stability for the anterior cervical column without any side-effects. We designed a novel S-type dynamic cage for C4-C5 level, using Polyetheretherketone (PEEK) material considering four different shapes namely: square, circle, rectangle and elliptical, for the central window to occupy bone graft...

In anterior cervical discectomy and fusion (ACDF), an interbody fusion device is an essential implant. An unsuitable interbody fusion device can cause postoperative complications, including subsidence and nonunion. We designed a customized intervertebral fusion device to reduce postoperative complications and validated it by finite element analysis. Herein, we built a non-homogeneous model of the C3-7 cervical spine. Three implant models (customized cage, commercial cage, and bone graft cage) were constructed and placed in the C45 cervical segment after ACDF surgery...

BACKGROUND: Degenerative disc disease is one of the most common ailments severely affecting the quality of life in elderly population. Cervical intervertebral body fusion devices are utilized to provide stability after surgical intervention for cervical pathology. In this study, we design a biomimetic porous spinal cage, and perform mechanical simulations to study its performances following American Society for Testing and Materials International (ASTM) standards before manufacturing to improve design process and decrease cost and consumption of material...

PURPOSE: Various factors have been examined in relation to cage subsidence risk, including cage material, cage geometry, bone mineral density, device type, surgical level, bone graft, and patient age. The present study aims to compare and synthesize the literature of both clinical and biomechanical studies to evaluate and present the factors associated with cage subsidence. METHODS: A comprehensive search of the literature from January 2003 to December 2021 was conducted using the PubMed and ScienceDirect databases by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines...

STUDY DESIGN: Pre-clinical biomechanical study of topology-optimization versus standard ring design for bioresorbable poly-ε-caprolactone cervical spine fusion cages delivering BMP-2 using a porcine model. OBJECTIVE: To evaluate range of motion (ROM) and bone fusion, as a function of topology optimization and bone morphogenetic protein-2 (BMP-2) delivery method. SUMMARY OF BACKGROUND DATA: 3D printing technology enables fabrication of topology-optimized cages using bioresorbable materials, offering several advantages including customization, and lower stiffness...

BACKGROUND: This study aimed to compare the biomechanical differences between anterior cervical discectomy and fusion (ACDF) with multiple-level separate plates and conventional long plates by using finite element analysis. METHODS: The following four finite element models were created to simulate various fixations: (1) C4-6 ACDF with multiple plates, (2) C4-6 ACDF with a single plate, (3) C3-6 ACDF with multiple plates, and (4) C3-6 ACDF with a single plate. The maximum Von-mises stress of the cage and fixation, compressive force of the adjacent intervertebral discs and range of motion (ROM) of different segments in the four models were calculated and analyzed...

Background: The traditional titanium mesh cage (TTMC) has become common as a classical instrument for Anterior Cervical Corpectomy and Fusion (ACCF), but a series of complications such as cage subsidence, adjacent segment degeneration (ASD), and implant-related complications by using the TTMC have often been reported in the previous literature. The aim of this study was to assess whether a novel anatomic titanium mesh cage (NTMC) could improve the biomechanical condition after surgery. Methods: The NTMC model consists of two spacers located on both sides of the TTMC which match the anatomic structure between the endplates by measuring patient preoperative cervical computed tomography (CT) data...

The porous interbody fusion cage could provide space and stable mechanical conditions for postoperative intervertebral bone ingrowth. It is considered to be an important implant in anterior cervical discectomy and internal fixation. In this study, two types of unit cells were designed using topology optimization method and introduced to the interbody fusion cage to improve the biomechanical performances of the cage. Topology optimization under two typically loading conditions was first conducted to obtain two unit cells (O-unit cell and D-unit cell) with the same volume fraction...

BACKGROUND: No-profile anterior cervical discectomy and fusion (ACDF) devices are commonplace in spinal surgery. Contained within the intervertebral margins, these devices diminish risks associated with anterior cervical plating, while also marginalizing cage migration and subsidence. However, these devices have been limited in their scope of implant material. Accordingly, a no-profile ACDF (npACDF) device supporting a machined allograft implant body with a connected load-sharing fixation interface was developed...

Introduction: Anterior cervical discectomy and fusion (ACDF) is a widely accepted surgical procedure in the treatment of cervical radiculopathy and myelopathy. A solid interbody fusion is of critical significance in achieving satisfactory outcomes after ACDF. However, the current radiographic techniques to determine the degree of fusion are inaccurate and radiative. Several animal experiments suggested that the mechanical load on the spinal instrumentation could reflect the fusion process and evaluated the stability of implant...

BACKGROUND: The plate-to-disc distance (PDD) is an important factor affecting the degeneration of adjacent segments after anterior cervical discectomy and fusion (ACDF). However, the most suitable PDD is controversial. This study examined the adjacent intervertebral disc stress, bone graft stress, titanium plate stress and screw stress to evaluate the biomechanical effect of different PDD on surgical segment and adjacent segment following C5/C6 ACDF. METHODS: We constructed 10 preoperative finite element models of intact C4-C7 segments and validated them in the present study...

Double traumatic non-contiguous lesions of the subaxial cervical region are a rare event mostly caused by multiple, simultaneous or rapidly consecutive high-energy-impact traumas. The modality of treatment chosen for these lesions must be related to local lower cervical spine biomechanics. We present the case of a 59 year-old patient who suffered a subaxial cervical spine double fracture-dislocation following a complex-dynamic trauma. Radiological imaging displayed a C4-C5 and C7-T1 fracture-dislocation with cord signal intensity abnormalities...

BACKGROUND: The decision to treat multilevel cervical spondylotic myelopathy (MCSM) remains controversial. The purpose of this study is to compare the biomechanical characteristics of the intervertebral discs at the adjacent segments and internal fixation, and to provide scientific experimental evidence for surgical treatment of MCSM. METHODS: An intact C2-C7 cervical spine model was developed and validated. Four additional models were developed from the fusion model, including multilevel anterior cervical discectomy and fusion (mACDF), anterior cervical corpectomy and fusion (ACCF), hybrid decompression and fusion (HDF), and mACDF with cage alone (mACDF-CA)...