Our objective was to identify precise mechanical metrics of the proximal tibia which differentiated OA and normal knees. We developed subject-specific FE models for 14 participants (7 OA, 7 normal) ...who were imaged three times each for assessing precision (repeatability). We assessed various mechanical metrics (minimum principal and von Mises stress and strain as well as structural stiffness) across the proximal tibia for each subject. In vivo precision of these mechanical metrics was assessed using CV%
. We performed parametric and non-parametric statistical analyses and determined Cohen's d effect sizes to explore differences between OA and normal knees. For all FE-based mechanical metrics, average CV%
was less than 6%. Minimum principal stress was, on average, 75% higher in OA versus normal knees while minimum principal strain values did not differ. No difference was observed in structural stiffness. FE modeling could precisely quantify and differentiate mechanical metrics variations in normal and OA knees, in vivo. This study suggests that bone stress patterns may be important for understanding OA pathogenesis at the knee.
Modeling stability post zygomatic fracture reconstruction Arjmand, Hanieh; Fialkov, Jeffrey A.; Whyne, Cari M.
Journal of plastic, reconstructive & aesthetic surgery,
April 2024, 2024-Apr, 2024-04-00, 20240401, Volume:
91
Journal Article
Peer reviewed
Zygomaticomaxillary complex (ZMC) fracture repair is one of the most common surgical procedures performed in craniomaxillofacial trauma management. Miniplates and screws are used to stabilize the ...fractured bone using small local incisions, however, these procedures are not infrequently associated with hardware-related post-operative complications. The amount of fixation hardware utilized varies depending on the fracture pattern and surgical judgment, with three-point fixation being the conventionally accepted treatment. However, limited experimental testing and clinical studies have suggested that ZMC stabilization may be achieved with less than three-point fixation. In this study, we utilized a previously developed finite element modeling approach that allows for detailed bone and muscle representation to study the mechanical behavior of the fractured craniomaxillofacial skeleton (CMFS) under one, two, or three-point fixation of the ZMC. Results suggest that using a miniplate along the infraorbital rim in three-point fixation increases the amount of strain and load transfer to this region, rather than offloading the bone. Two-point (zygomaticomaxillary and zygomaticofrontal) fixation yielded strain patterns most similar to the intact CMFS. One-point (zygomaticofrontal) fixation resulted in higher tensile and compressive strains in the zygomaticofrontal region and the zygomatic arch, along with a higher tensile strain on the zygomatic body. These modeling results provide biomechanical evidence for the concept of over-engineering in the stabilization of facial fractures. Furthermore, they support previous suggestions that less than three-point fixation of ZMC fractures may be adequate to achieve uneventful healing.
Fixation is critical in zygomaticomaxillary complex (ZMC) fractures to avoid malunion; however, controversy exists as to how much hardware is required to achieve adequate stability. Current fixation ...regimens may not represent the minimum stabilization needed for uneventful healing. Craniomaxillofacial (CMF) computational models have shown limited load transmission through the infraorbital rim (IOR), and a previous experimental study of ZMC fractures has suggested that IOR plating does not alter CMF bone strain patterns. This study aimed to measure the impact of stabilization on fracture site displacement under muscle loading, testing the hypothesis that three-point fixation is not critical for ZMC fracture stability. Four ZMC complex fractures were simulated on two cadaveric samples and stabilized with three-point plating. Displacements simulating mouth openings of 20 mm and 30 mm were applied to the mandible using a custom apparatus. Fracture gap displacement under load was measured at multiple points along each fracture line, and bone strain was captured using a combination of uniaxial and rosette gauges. Data capture was repeated with the IOR plate removed (two-point fixation) and with the zygomaticomaxillary plate removed (one-point fixation). Fracture displacement under muscle loading was consistent, with gaps of less than 1 mm in 95% of cases (range 0.05–1.44 mm), reflecting clinical stability. Large variabilities were observed in the strain measurements, which may reflect the complexity of CMFS load patterns and the sensitivity of strain values to gauge placement. This study supports the concept of hardware reduction, suggesting that two-point (or even one-point) fixation may provide sufficient stability for a ZMC fracture under applied muscle loading.
Purpose
The purpose of this paper is to present an analytical approximate solution of the nonlinear mathematical model of the bifilar pendulum.
Design/methodology/approach
First, the equation of ...motion derived based on the classical dynamics law by only an angular oscillation assumption and vertical oscillation is neglected. The energy balance method is applied to solve an established model and an analytical formulation has been obtained for the nonlinear frequency of the bifilar pendulum.
Findings
A comparison of results with those obtained by a numerical solution of the exact model (without any simplifications) shows the precise accuracy even for a large amplitude of oscillation.
Originality/value
The proposed model and solution are relatively simple and can be applied instead to a linear model for achieving accurate results.
Background and Aim: The third molar tooth lies with symptoms such as periodontal problems, caries, crowding, root resorption, cyst and tumor formation of the adjacent second molar. The purpose of ...this study was performed to evaluation of the position of mandibular third molar teeth and its effect on second adjacent molar teeth. Materials and Methods: Panoramic radiography were obtained from 264 patients with mandibular third molar hidden teeth referred to the Birjand School of Dentistry in 2018. The material and direction of their placement and the vertical position of the third molar tooth (based on the PELL & Gregory classification) and its placement angle (based on Winter classification) were determined. Also, the prevalence of distal caries, external root resorption, the amount of displacement, and the amount of inflammatory lesions and the cystic was examined in the adjacent second molar tooth. Data were analyzed using SPSS software (Version 19), and chi-square statistical test, p-values less than 0.05 were considered statistically significant. Results: The data from this study showed that most of the wisdom hidden teeth were in Class B and III of Pell and Gregory classification, had Mesial angle based on Winter classification. In 20.8% of patients with caries, there was 3% root canal resorption and 1.1% displacement of the second molar tooth, while no cases of inflammatory and cystic lesions in the second molar tooth were found due to the hidden third molar tooth. The Mesial and horizontal angles of impacted wisdom teeth were associated with increased risk of caries and root resorption of the second molar. Also, Class Bchr('39')s third molar teeth increased caries in second molar teeth. Conclusion: Most pathological problems were observed in Mesial, horizontal, and class B impaction. According to the observed relationship, it seems that the angle and depth of the hidden third molar should be taken into account considered when deciding whether or not to extract it.
OBJECTIVE To compare strain at the bone-pin and cast-pin interfaces among 3 transfixation pin-cast constructs applied to equine forelimbs. ANIMALS 15 forelimbs from 15 adult horses. PROCEDURES Limbs ...were randomly assigned to 1 of 3 constructs. Centrally threaded positive-profile pins were used for all constructs, and the most distal pin was placed just proximal to the epicondyles of the third metacarpal bone. Construct 1 consisted of two 6.3-mm-diameter pins spaced 4 cm apart at 30° to each other. Construct 2 was the same as construct 1 except the pins were placed 5 cm apart. Construct 3 consisted of four 4.8-mm-diameter pins spaced 2 cm apart and at 10° to one another. An osteotomy was created in the proximal phalanx. Strain gauges were attached to the cast and bone proximal to the pins and adjacent to the osteotomy. Limbs underwent compressive loading until failure. Simplified finite element models of constructs 1 and 3 were created to further evaluate strain and load transfer between the bone and cast. RESULTS Strain did not differ between constructs 1 and 2. Compared with the 2-pin constructs, construct 3 had less strain at the bone-pin interface and more strain at the cast-pin interface, which indicated a greater amount of load was transferred to the cast of the 4-pin construct than the cast of the 2-pin constructs. Finite element modeling supported those findings. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that the 4-pin construct was more effective in unloading the fractured bone than either 2-pin construct.
Cancer stem cells (CSCs) are subpopulation of cells which have been demonstrated in a variety of cancer models and involved in cancer initiation, progression, and development. Indeed, CSCs which seem ...to form a small percentage of tumor cells, display resembling characteristics to natural stem cells such as self-renewal, survival, differentiation, proliferation, and quiescence. Moreover, they have some characteristics that eventually can demonstrate the heterogeneity of cancer cells and tumor progression. On the other hand, another aspect of CSCs that has been recognized as a central concern facing cancer patients is resistance to mainstays of cancer treatment such as chemotherapy and radiation. Owing to these details and the stated stemness capabilities, these immature progenitors of cancerous cells can constantly persist after different therapies and cause tumor regrowth or metastasis. Further, in both normal development and malignancy, cellular metabolism and stemness are intricately linked and CSCs dominant metabolic phenotype changes across tumor entities, patients, and tumor subclones. Hence, CSCs can be determined as one of the factors that correlate to the failure of common therapeutic approaches in cancer treatment. In this context, researchers are searching out new alternative or complementary therapies such as targeted methods to fight against cancer. Molecular docking is one of the computational modeling methods that has a new promise in cancer cell targeting through drug designing and discovering programs. In a simple definition, molecular docking methods are used to determine the metabolic interaction between two molecules and find the best orientation of a ligand to its molecular target with minimal free energy in the formation of a stable complex. As a comprehensive approach, this computational drug design method can be thought more cost-effective and time-saving compare to other conventional methods in cancer treatment. In addition, increasing productivity and quality in pharmaceutical research can be another advantage of this molecular modeling method. Therefore, in recent years, it can be concluded that molecular docking can be considered as one of the novel strategies at the forefront of the cancer battle via targeting cancer stem cell metabolic processes.
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