Biomechanical evaluation of a short-rod technique for lumbar fixation surgery

Abstract

Objective: The purpose of this study was to analyze the stability and instrument-related complications associated with fixation of the lumbar spine using the Short-Rod (SR) technique.Methods: Using finite element analysis, this study assessed the stability of a bilateral lumbar fixation system when inserting the pedicle screws at angles of 10°, 15°, and 20° to the endplate in the sagittal plane. Using the most stable construct with a screw angle, the model was then assessed with different rod lengths of 25, 30, 35, and 45 mm. The optimal screw inclination angle and rod length were incorporated into the SR model and compared against traditional parallel screw insertion (pedicle screws in parallel to the endplate, PPS) in terms of the stability and risk of instrument-related complications. The following parameters were evaluated using the validated L4–L5 lumbar finite element model: axial stiffness, range of motion (ROM), stress on the endplate and facet joint, von-Mises stress on the contact surface between the screw and rod (CSSR), and screw displacement.Results: The results showed that the SR model with a 15° screw inclination angle and 35 mm rod length was superior in terms of construct stability and risk of complications. Compared to the PPS model, the SR model had lower stiffness, lower ROM, less screw displacement, and lower stress on the facet cartilage, the CSSR, and screws. However, the SR model also suffered more stress on the endplate in flexion and lateral bending.Conclusion: The SR technique with a 15° screw inclination and 35 mm rod length offers good lumbar stability with a low risk of instrument-related complications.

Biomechanical performance of the novel assembled uncovertebral joint fusion cage in single-level anterior cervical discectomy and fusion: A finite element analysis

“…Our results have suggested greater stress in the uncovertebral joint area, which could also explain the increased speed and quality of bone healing with bone grafting in the uncovertebral joint area during the short term. The method of immediate postoperative testing of biomechanical properties was adopted in most studies ( Wu et al, 2019 ; Huang et al, 2022 ; Liu et al, 2022 ; Lv et al, 2022 ; Zhang et al, 2022a ). Considering that osseointegration is a long-term process, a longer dynamic observation of the stress distribution in the region of the uncovertebral joint is necessary.…”

“…Fourth, this study simplifies the musculoskeletal system, and the results under this ideal condition did not fully reflect the actual postoperative situation. Although this study aimed to provide a biomechanical reference for clinics, the manipulation of the muscular–ligamentous system in this finite analysis was based on previous literature ( Fu et al, 2022 ; Huang et al, 2022 ; Shen et al, 2022 ; Zhang et al, 2022b ). Last, linear elastic materials were adopted for the cervical vertebral body and intervertebral disc.…”

Hybrid pedicle screw and modified cortical bone trajectory technique in transforaminal lumbar interbody fusion at L4-L5 segment: finite element analysis

“…BPS-BMCS group offered the superior stability in extension and rotation, but in flexion and lateral bending. Huang et al [ 29 ] demonstrated that the inter-screw angle of 15° between the screw at the cranial and caudal segment resulted in the lowest L4-L5 segmental ROM in flexion, extension, and rotation. In this study, the inter-screw angle was 8° in the BPS-BMCS group and 33° in the BMCS-BPS group.…”

Biomechanical evaluation of a novel intervertebral disc repair technique for large box-shaped ruptures

“…Figure 1 shows the 3-dimensional lumbar model used in this study, which was modified from a model previously developed by the research team (L4-L5) ( Huang et al, 2022 ). Some studies report the non-homogeneous property of vertebrae, but other studies also report the reliability of vertebrae being isotropic ( Hu et al, 2019 ).…”

“…Finite element model (FEM) analysis allows for one input factor such as the force or moment to be altered while keeping other factors constant. This is a convenient and inexpensive method of simulating different physiological conditions and has been widely used for assessing lumbar implants ( Yao et al, 2006 ; Huang et al, 2022 ).…”