The Role of Trabecular, Ligamentous-Intervertebral Disk and Facet Joints Systems: A Finite Element Analysis in the L4-S1 Vertebrae.

STUDY DESIGN: Descriptive. OBJECTIVES: Trabecular bone in the vertebrae is critical for the distribution of load and stress throughout the neuroaxis, as well as the intervertebral disk, ligamentous complex, and facet joints. The objective was to assess the stress and strain distribution of the L4-S1 spine segment by a finite element analysis. METHODS: A lumbosacral spine model was built based on a CT-Scan. Trabecular-to-cortical bone distribution, ligaments, intervertebral disk, and facet joints with cartilage were included. A perpendicular force was applied over the L4 upper terminal plate of 300 N, 460 N and 600 N in neutral, plus 5 Nm and 7.5 Nm for flexion and extension movements. Maximum principal stress and total deformation were the main studied variables. RESULTS: Trabecular bone confers resistance to axial loads on the vertebrae by elastic capacity and stress distribution. MPS and TD showed axial stress attenuation in the nucleus pulposus and longitudinal ligaments, as well as load distribution capacity. Facet joints and discontinuous ligaments showed greater TD values in flexion moments but greater MPS values in extension, conferring stability to the lumbosacral junction and axial load distribution. CONCLUSION: We propose 3 anatomical systems for axial load distribution and stress attenuation in the lumbosacral junction. Trabecular bone distributes loads, while the ligamentous-intervertebral disk transmits and attenuate axial stress. Facet joints and discontinuous ligaments act as stabilizers for flexion and extension postures. Overall, the relationship between trabecular bone, ligamentous-intervertebral disk complex and facet joints is necessary for an efficient load distribution and segmental axial stress reduction.This slide can be retrieved from the Global Spine Congress 2023.

Biomechanical behavior of an alveolar graft under maxillary therapies.

Cleft lip and palate is a congenital defect that affects the oral cavity. Depending on its severity, alveolar graft surgery and maxillary orthopedic therapies must be carried out as a part of the treatment. It is widely accepted that the therapies should be performed before grafting. Nevertheless, some authors have suggested that mechanical stimuli such as those from the maxillary therapies could improve the success rate of the graft. The aim of this study is to computationally determine the effect of maxillary therapies loads on the biomechanical response of an alveolar graft with different degrees of ossification. We also explore how the transverse width of the cleft affects the graft behavior and compare results with a non-cleft skull. Results suggest that stresses increase within the graft as it ossifies and are greater if maxillary expansion therapy is applied. This has consequences in the bone remodeling processes that are necessary for the graft osseointegration. Maxillary orthopedic therapies after graft surgery could be considered as a part of the treatment since they seem to act as a positive extra stimulus that can benefit the graft.

Metodología alternativa para elaborar modelos geométricos de anatomía dental / Alternative methodology to elaborate geometrical models of dental anatomy

Se pretende proponer una metodología alternativa para elaborar modelos geométricos de anatomías dentales para estructuras de dientes incisivos y caninos, y crear modelos CAD apropiados para un posterior estudio por método. Se describe la metodología aplicándola a la construcción de un Incisivo maxilar lateral izquierdo, donde posteriormente se analiza, a modo de ejemplo, el comportamiento del elemento creado bajo una carga de 200 N; esta carga genera un desplazamiento de 27 pm y un esfuerzo Von Mises máximo de 92.588 MPa.

The aim of this article is to propose an alternative methodology to elaborate geometrical models of dental anatomy for incisors and canines structures, and to create appropriate CAD models for a further numerical method study. The methodology is described applying it to the construction of a maxillary left lateral incisor. Then the crated element is analyzed, as an example, under a load of 200 N. This load generates a displacement of 27 pm and a maximum Von Mises stress of 92.588 MPa.