Search Results (119)

Mandibular angle fractures pose a significant clinical challenge in maxillofacial surgery, and conventional fixation systems often show merely adequate biomechanical performance. This study presents a new mini-plate geometric configuration and outlines its rigorous verification and a preliminary validation procedure. The proposed ‘U’-shaped grade 4 titanium mini-plate with self-tapping screws was developed specifically for the stable fixation of mandibular angle fractures. A three-dimensional mandible model incorporating an angular fracture gap exceeding 1 mm was constructed and analyzed using SolidWorks. Finite Element Analysis (FEA) was employed as a verification tool to evaluate stress, strain, and displacement distributions in the mandibular ramus, plate, and screws under bilateral masticatory muscle loading, with material integrity assessed against yield-strength thresholds using von Mises’ stress theory. Rapid and functional prototypes were subsequently fabricated to physically validate the proposed mini-plate. The maximum stress across the entire model was 446.8 MPa, localized at the middle lower screw, while the maximum stress at the designed plate was 110 MPa, which remains well within the safe limits and is approximately 60.7% lower than the reported maximum stress values for conventional fixation systems. The new mini-plate exhibited robust biomechanical performance, offering a more favorable mechanical environment conducive to bone healing. Full article

Sacroiliac joint (SIJ) disruption alters posterior pelvic ring stability and can produce abnormal sacral stress redistribution; the symmetry of sacral load transfer following different fixation strategies remains controversial. This study compared sacral stress patterns under unilateral and bilateral SIJ instability for three fixation constructs using a three-dimensional finite element (FE) model. A lumbosacral–pelvic FE model was reconstructed from computed tomography data of a healthy adult and validated against previously published pelvic biomechanical data. SIJ instability was simulated by reducing the friction coefficient to represent ligamentous failure. Three fixation constructs were analyzed: anterior plate combined with posterior screw fixation (Model 1), spinopelvic fixation (Model 2), and hybrid fixation (Model 3). A 750 N axial compressive load was applied to simulate static standing. Peak sacral von Mises stress, stress amplification factors (SAFs), and left–right asymmetry ratios were computed and compared with the intact reference. Model 1 produced the highest sacral stress amplification (SAF = 3.46 under unilateral instability; peak stress 265.40 MPa). Model 2 reduced peak sacral stress (125.66 MPa under bilateral instability; SAF = 1.64), but values remained above the intact-model baseline. Model 3 yielded sacral stress closest to the intact condition under bilateral instability (81.64 MPa; SAF = 1.06), with near-symmetric load distribution in the bilateral injury configuration. Fixation topology strongly influenced sacral load transfer: hybrid fixation (Model 3) produced sacral stress magnitudes closest to the intact model, particularly under bilateral instability, whereas spinopelvic fixation (Model 2) showed more consistent left–right symmetry under unilateral injury. No single construct was superior across all symmetry-related outcomes. Hybrid stabilization may provide a biomechanically balanced approach to highly unstable posterior pelvic ring injuries under the simulated static axial-loading conditions. Full article

Background/Objectives: Patient-specific subperiosteal implants are increasingly used to treat severely atrophic ridges due to advances in digital planning and additive manufacturing. This study aimed to evaluate the effects of material type and implant configuration on stress distribution in subperiosteal implant systems and to compare their overall biomechanical performance using a multi-criteria decision framework. Methods: A three-dimensional model of a severely atrophic maxilla was reconstructed to simulate four clinical scenarios combining two configurations (one-piece and two-piece) and two materials (titanium and 60% carbon fiber-reinforced polyetheretherketone). Finite element analysis was conducted to assess stress distribution within the implant body, fixation screws, prosthetic framework, and surrounding bone under vertical and oblique loading conditions. Maximum and minimum principal stresses were evaluated in bone, whereas von Mises stresses were calculated for implant components. The resulting biomechanical indicators were subsequently integrated using an entropy weight–TOPSIS multi-criteria decision analysis. Results: Principal stresses in the surrounding bone showed minimal variation between titanium and 60% carbon fiber-reinforced polyetheretherketone across all configurations. Implant configuration had a more pronounced effect on implant body stress. Under oblique loading, the two-piece configuration demonstrated substantially higher implant stresses than the one-piece design, whereas under vertical loading, lower implant stresses were observed in the two-piece configuration. The multi-criteria analysis ranked the one-piece titanium model highest under oblique loading and the two-piece titanium model highest under vertical loading. Conclusions: Implant configuration and loading direction influenced biomechanical behavior more than material selection in patient-specific subperiosteal implants. Full article

Background/Objectives: Due to the inherent rotational instability of the proximal fragment in unstable basicervical intertrochanteric (IT) fractures, the biomechanical effect of lag screw position may differ from that observed in typical unstable IT fractures. This study aimed to evaluate the influence of lag screw positioning on proximal fragment displacement and stress distribution after cephalomedullary nailing (CMN) in unstable basicervical IT fractures using finite element analysis. Methods: Twelve finite element models of unstable basicervical IT fractures fixed with a CM nail were constructed with lag screws placed in four anteroposterior (AP) positions (superior 5 mm, center, inferior 5 mm, and inferior 10 mm) and three axial positions (anterior, center, and posterior). The positional change of the proximal fragment and stress concentration on the nail construct were measured. Results: In this computational model, proximal fragment displacement and stress concentration, including peak von Mises stress and mean stress over a region of interest, increased as the lag screw was positioned more inferiorly on the AP view and more posteriorly on the axial view. Conversely, a relatively superior-anterior lag screw position was associated with the lowest proximal fragment displacement and reduced stress concentration on the nail construct and around the lag screw tip. Conclusions: Within the limitations of this finite element analysis using a single femoral model and axial loading condition, a relatively superior-anterior lag screw position was associated with more favorable biomechanical behavior compared with more inferior or posterior positions. These findings should be interpreted as hypothesis-generating biomechanical observations rather than direct clinical guidance. Full article

Surgical fixation techniques for bone fracture healing are well established and effective; however, opportunities remain to improve both functional outcomes and the patient experience. The Biofiligree^® concept integrates medicine, engineering, and design by reimagining conventional osteosynthesis plates as both therapeutic and aesthetic devices. Inspired by traditional Portuguese filigree, these plates allow patient participation through personalized geometries, patterns, or engravings and may later be transformed into wearable jewellery after removal, preserving them as symbolic artefacts of recovery. This study introduces and biomechanically evaluates a novel calcaneal fixation plate incorporating the biofiligree geometry concept. A biofiligree plate was designed for calcaneus fracture fixation and manufactured in stainless steel 306L. Experimental testing was conducted on synthetic composite calcaneus bone models to simulate anatomical conditions and compare the new design with a standard commercial plate. The biofiligree plate, 2 mm thick, was fixed using five screws and two percutaneous screws positioned at 45° to compress the fracture line. Results demonstrated comparable biomechanical performance between both systems, with similar strain distributions and fracture stabilization. The biofiligree plate showed stresses around 430 MPa and fracture displacement below 0.7 mm. Fixation stiffness values were 1445 N/mm for intact calcaneus, 1065 N/mm for the commercial plate, and 725 N/mm for the biofiligree plate, indicating adequate support for bone healing. Full article

Reliable and energy-efficient capacity control in high-pressure single-rotor screw compressors requires precise regulation of adjustable ring mechanisms operating under combined gas and thermal loading. Thermo-mechanical deformation, friction-induced torque demand, and stress concentration near discharge windows significantly influence structural integrity, clearance stability, and actuation performance. This study presents an integrated thermo-structural and analytical investigation of a regulating ring system with a hydraulic wedge-groove drive concept. Three groups of geometric variants (nine configurations total) were analyzed using coupled Steady-State Thermal and Static Structural finite element modeling in ANSYS 19.2. Thermal asymmetry between suction (22 °C) and discharge (120 °C) regions produced peak thermally induced deformation of 0.17–0.18 mm, consuming up to 60–70% of nominal operating clearance. Neglecting thermal effects underestimated peak thermally induced structural deformation of the regulating ring by 12–15%. Among the configurations, variant 2b provided the most balanced response, reducing peak equivalent stress by 12–15% and required actuation torque by 8–11%. An analytical model for friction torque and driving force was derived based on distributed contact pressure. The results reveal quadratic sensitivity of torque to contact radius and strong dependence on groove geometry. The proposed framework supports reliable clearance design and efficient actuation in heavy-duty rotating machinery. Full article

This Finite Element Analysis study evaluated the biomechanical responses associated with posterior tooth intrusion using clear aligners in conjunction with buccal and palatal mini-screw anchorage. Three-dimensional finite element models were reconstructed from cone beam computed tomography images obtained from patients without craniofacial anomalies. To assess the differential effects of buccal versus palatal attachment placement in combination with a mini-screw-supported closing coil spring, two configurations of the maxillary arch were created: Model A (right side) and Model B (left side). Biomechanical parameters—including stress distribution, patterns of tooth displacement, and anchorage stability—were systematically assessed using finite element analysis. Analysis of Model A revealed buccal crown inclination and moderate extrusion of the first premolar, whereas the first molar showed limited mesial displacement along with mild buccal tipping and extrusion. In contrast, Model B revealed palatal crown inclination of the first premolar, accompanied by buccal root torque and minor intrusion; the first molar demonstrated enhanced vertical control with palatal root torque. The incorporation of palatal mini-screw anchorage in Model A contributed to diminished stress levels and reduced tooth displacement, suggesting a tendency toward more favorable force distribution and anchorage stability under the simulated conditions. Conversely, Model B experienced increased mechanical loading and more pronounced displacement. Full article

Cervical spondylosis is a common cause of spinal cord dysfunction, and anterior cervical discectomy and fusion (ACDF) is widely employed when conservative treatment fails. Conventional implant systems such as the cervical cage with plate (CCP) and zero-profile stand-alone cage (ZPSC) are commonly used to enhance spinal stability and promote fusion, but they are associated with complications including dysphagia and adjacent segment degeneration. To address these limitations, a novel flexible plate cage system (FPCS) has been developed to optimize biomechanical performance while minimizing surgical risk. In this study, a finite element model of the C3–T1 cervical spine was constructed to simulate ACDF at the C5–C6 level using CCP, ZPSC, and FPCS implants. Under standardized loading conditions, von Mises stress was analyzed in the bone, intervertebral disc, endplates, cage, and screws, using the mean of the top 5% stress values to ensure accuracy. All surgical models showed increased stress compared to the intact reference spine. The ZPSC model exhibited the highest stress in the cage and screws, suggesting a more concentrated load path. The CCP model showed a more evenly distributed stress profile, particularly affecting the inferior adjacent segment. The FPCS model demonstrated moderate cage stress, reduced screw stress, and the highest plate stress, indicating a design that effectively redirects mechanical load from the screw-bone interface toward the anterior plate. This may be related to the unique structural configuration of the FPCS, which secures screws horizontally into the anterior vertebral body without penetrating the endplates. These findings suggest that the FPCS may offer a biomechanically favorable alternative to existing ACDF implants. Full article

Background and Objectives: The management of periprosthetic tibial fractures distal to revision Total Knee Arthroplasty (TKA) presents a biomechanical challenge, often requiring extramedullary locking plates when long stems preclude nailing. While in femoral fractures the gap between the stem and plate is a well-documented stress riser, requiring implant overlap to prevent an inter-implant fracture, this specific biomechanical scenario has not been studied in the tibia, and it remains unclear if the femoral dogma of mandatory overlap applies to the straight, centrically loaded tibial anatomy. This study utilized Finite Element Analysis (FEA) to evaluate stress distribution in the tibial inter-implant gap. Materials and Methods: A comparative FEA was performed using a validated standardized tibia model simulating a healed distal fracture. Two cemented revision TKA constructs (50 mm and 80 mm stems) were modeled. These were paired with medial locking plates of varying lengths (10, 12, and 14 holes) to create different inter-implant distances. Eight distinct configurations, including non-plated controls, were subjected to physiological axial compression and three-point bending. Outcome measures included von Mises stress and total displacement. Results: The analysis revealed no significant stress concentration in the bone within the inter-implant zone across all plated models, regardless of the gap size. Instead, the addition of plates universally reduced bone stress compared to controls, effectively transferring load to the fixation hardware. Peak stresses were consistently observed in the proximal locking screws rather than the bone gap. The longest plates (14 holes) offered superior construct rigidity and stress distribution. Conclusions: Under the conditions evaluated in this preclinical finite element model, the tibia does not exhibit a biomechanical requirement for implant overlap to prevent stress risers. Our findings suggest that extramedullary fixation with the longest available anatomical locking plate represents a biomechanically plausible strategy for these fractures, even if an inter-implant gap remains. Full article

Introduction: Type II odontoid process fractures are common in the adult population, and anterior screw fixation aims to restore C1–C2 complex stability while preserving cervical motion. This study focuses on the numerical analysis of odontoid fractures, evaluating the structural behavior after anterior screw fixation using finite element simulations. Methods: Forty-eight patients (males, females, 74 years old on average) diagnosed with type II odontoid fractures and treated surgically between 2015 and 2023 were included in the study. Various loading conditions (magnitude and direction) were simulated to analyze displacements and stress distributions after screw insertion. Results: Screw fixation significantly fixes fractured vertebrae, but stress and deformation are considerably larger than in unfractured cases. Posterior oblique loads produced the highest stress concentrations, particularly at the base of the odontoid and the screw-bone interface. Male models exhibited greater total deformations and stresses under the same loading conditions, suggesting relevant biomechanical differences based on sex. Conclusions: Anterior odontoid screw fixation provides effective stabilization in type II odontoid fractures, although its performance depends on factors such as load vector and patient-specific anatomical characteristics. These findings support the use of FEM simulation as a valuable tool for personalized surgical analysis. Full article

Background: Mandibular advancement is a commonly performed surgical procedure for the treatment of mandibular retrognathia and Class II dentofacial deformities; however, large advancements impose increased mechanical demands on fixation systems. Despite the availability of various fixation strategies, standard straight plate systems remain widely used worldwide due to their availability, cost-effectiveness, and clinical familiarity. Continuous biomechanical evaluation of these systems is therefore required to optimize stability and performance under demanding conditions. Objectives: The aim of this study was to evaluate the influence of plate design, plate thickness, and fixation architecture on the mechanical stability of mandibular advancement using finite element analysis. Methods: A three-dimensional finite element model simulating a unilateral mandibular osteotomy with a 10 mm gap was generated as mandibular advancement was developed. Fifteen fixation configurations were analyzed, including variations in plate design (simple and reinforced plates with partial or total inferior mesh extension), plate thickness (0.8 mm and 1.0 mm), and fixation architecture using independent plate systems (LN) or integrated fixation systems (FM). A vertical load was applied to the lower central incisor to simulate functional loading. Outcome measures included global equivalent stress considering screws and plate, equivalent stress within the plate, and global deformation of the fixation system. Results: The analyses demonstrated distinct mechanical behaviors among the evaluated configurations. Differences in stress distribution and deformation were observed according to plate design, thickness, and fixation architecture. Reinforced designs, increased plate thickness, and integrated fixation systems showed reduced deformation and more favorable stress distribution when compared with simple plate configurations. Conclusions: Plate design, thickness, and fixation architecture influenced the mechanical stability of mandibular advancement, supporting the importance of biomechanical optimization of standard fixation systems, particularly in large mandibular advancements. Full article

Threaded component fatigue failure is a severe issue in cyclically loaded mechanical systems, and the service life in these systems is controlled primarily by stress concentration at the thread root, especially in loading regimes dominated by bending. Rounded thread profiles such as knuckle threads have been thought to improve fatigue performance, although this is mostly due to the assumption being made on the basis of axial loading, the numerical stress analysis, and/or isolated stress-concentration analyses. This paper presents an experimental study on the fatigue behavior of knuckle-thread and conventional screw-thread specimens manufactured from AISI 1045 steel under rotating bending loading to determine the effects of thread geometry on fatigue life and damage mechanisms. Fatigue testing was conducted at varying stress levels to develop comparative stress–life (S–N) curves, the analytical relation being used in determining the stress-concentration factor, and standard literature techniques have been used in the analysis of fracture-surface in order to investigate the behavior of crack initiation and propagation. Results indicate that knuckle threads exhibit a lower stress concentration factor (K_t ≈ 1.59) than screw threads (K_t ≈ 2.11), resulting in longer fatigue life at the same nominal stress level, particularly in the high-cycle life regime. Fractographic research also indicates that knuckle threads enhance delayed crack initiation and more evenly distributed circumferential crack propagation, but screw threads show highly localized crack initiation and rapid radial propagation of cracks, resulting in earlier unstable fracture. These findings provide new experimental evidence that the improved fatigue performance of knuckle threads during rotating bending is linked to fundamental change in fatigue damage mechanism rather than to stress alleviation alone, thereby offering quantitative supporting guidance in designing fatigue-sensitive threaded components to experience cyclic bending. Full article

Background/Objectives: Sagittal split ramus osteotomy (SSRO) is a widely used method in the treatment of mandibular deformities. However, high parafunctional forces associated with bruxism can negatively affect stability at the osteotomy site. Botulinum toxin A (BoNT-A), which reduces masseter activity, is considered an additional approach to controlling these forces. Methods: In this comparative finite element study, five different fixation configurations were created on a three-dimensional mandibular model and evaluated under identical boundary conditions using both a 1000 N bruxism-related parafunctional loading and a standardized force-reduction scenario. The stress distributions and displacement amounts on the cortical bone, screws, and plates were examined in each model. Results: The stress distribution was more balanced in the model with double plates, whereas the stress and displacement values were found to be greater for fixations with single plates and only bicortical screws. Under the standardized force-reduction scenario, lower stress and displacement values were observed across all the models. Conclusions: Among the evaluated fixation configurations, the double-plate model demonstrated the most balanced stress distribution. Under the standardized force-reduction scenario, lower stress and displacement values were observed across all the models; these findings reflect the load sensitivity of the fixation constructs and should not be interpreted as evidence of clinical efficacy. Full article

A demountable connection is necessary to enable quick and easy replacement of high-temperature superconducting (HTS) tape samples during cryogenic (77 K) testing, particularly when investigating their application in superconducting fault current limiters (SFCLs). Testing HTS tapes for application in SFCLs involves inducing their transition from the superconducting state to the resistive state, which can result in sample damage. The contact resistance of the HTS tape to the current lead depends on the area and on the uniform pressure. Stress distribution in screwed connections with two, four and six screws was analysed using a solid model to compare them and achieve the uniform contact essential for minimising contact resistance in cryogenic conditions. The analysis indicated a solution that provides the most uniform pressure distribution across the HTS tape surface. This solution was utilised in subsequent calculations of thermal shrinkage, and for the determination of the optimal disc spring stack configuration. It is imperative that the compensating disc springs maintain the requisite pressure of the copper block on the tape across the entire operational temperature range (room to cryogenic). Furthermore, the disc springs must provide adequate stroke to compensate for the thermal shrinkage of a copper block and an aluminium clamp. Full article

Objectives: The aim of this study was to compare the stiffness-related mechanical response and peak von Mises stress distribution of low-profile 2.4 mm mandibular reconstruction systems (a conventional reconstruction plate, a 3D grid-type plate, and a customized plate) in a virtual atrophic mandible model with a 5 cm segmental defect. Materials and Methods: A CT-based three-dimensional mandible model was created and instrumented with three plate configurations (G1–G3). Linear static finite element analyses were performed under a 300-N masticatory load combined with literature-based muscle force vectors. Peak von Mises stresses were recorded for plates and screws, and the locations of maximum stress concentration were identified. Results: Peak plate stress was highest in the conventional reconstruction plate (G1: 695.5 MPa), followed by the 3D grid-type plate (G2: 595.6 MPa), and lowest in the customized plate (G3: 185.2 MPa). The peak screw stress was 692.9 MPa (G1), 898.0 MPa (G2), and 595.6 MPa (G3). The 3D grid-type plate increased construct stiffness but shifted stress concentration toward the mandibular angle and adjacent screws, whereas the customized plate reduced the peak plate stress and limited the extent of the high-stress region across the defect. Conclusions: Within the limitations of a linear static FEA (stiffness/stress distribution rather than failure load or fatigue resistance), the customized plate (G3) demonstrated the most favorable biomechanical performance (lowest peak plate stress). The 3D grid-type plate (G2) reduced peak plate stress compared with the conventional design (G1) but produced the highest peak screw stress. Practical considerations such as manufacturing lead time and resource requirements may favor off-the-shelf plates; however, a formal cost or operative-time analysis was not performed. Full article