Torsion Instability Research Articles

Compressive bearing capacity of steel dual-angle with cruciform welding filler plates based on failure modes

The bearing capacity of steel dual-angle with cruciform welding filler plates (i.e., DACWP) under axial compression is the primary purpose of this paper. Six DACWP specimens were prepared with different width-thickness ratios (i.e., 15.63, 12.50, 10.42) and slenderness ratios (i.e., 45, 75). Axial compression tests were carried out to analyze the failure mode, load-displacement curve, and load-strain history of the specimens. Subsequently, a finite element model was established and calibrated by test results, providing further insights into the influence of the slenderness ratio and width-thickness ratio on the bearing capacity of DACWP. Finally, a calculation method of bearing capacity based on different failure modes was proposed. The results show that, with a constant width-thickness ratio, the DACWP transits from torsion failure to bending failure with the increase of slenderness ratio. Particularly, the transition slenderness ratio of failure is found to be proportional to the slenderness ratio and the width-thickness ratio. In the case of torsion instability, the slenderness ratio has little effect on the bearing capacity, while the width-thickness ratio exhibits an opposite effect. Specifically, the bearing capacity of DACWP decreases with the increase of slenderness ratio and width-thickness ratio. The calculation formula proposed in this paper can be used to calculate the bearing capacity of DACWP.

Increased tibial tuberosity torsion has the greatest predictive value in patients with patellofemoral instability compared to other commonly assessed parameters.

The multifactorial nature of patellofemoral instability requires a comprehensive assessment of the affected patients. While an association between tibial tuberosity (TT) torsion and patellofemoral instability is known, its specific effect has not yet been investigated. This study investigated the effect of TT torsion on patellofemoral instability. This retrospective cohort study compared patients who underwent surgical intervention for patellofemoral instability and asymptomatic controls. TT torsion was measured in addition to other commonly assessed risk factors for patellofemoral instability using standardised computed tomography (CT) data of the lower extremities. The diagnostic performances of the assessed parameters were evaluated using receiver operating characteristic curveanalysis and odds ratios (ORs) were calculated. The patellofemoral instability group consisted of 79 knees, compared to 72 knees in the asymptomatic control group. Both groups differed significantly in all assessed parameters (p < 0.001), except for tibial torsion (n.s.). Among all parameters, TT torsion presented the best diagnostic performance for predicting patellar instability with an area under the curve of 0.95 (95% confidence interval [CI], 0.91-0.98; p < 0.001). A cut-off value of 17.7° yielded a 0.87 sensitivity and 0.89 specificity to predict patellar instability (OR, 55.2; 95% CI, 20.5-148.6; p < 0.001). Amongthe evaluated risk factors, TT torsion had the highest predictive value for patellofemoral instability. Patients with TT torsions ≥ 17.7° showed a 55-fold increased probability of patellofemoral instability. Therefore, TT torsion should be included in the assessment of patients with patellofemoral instability. Level III.

Failure behavior of steel dual-angle with cruciform welding filler plates under compression

This paper focuses on the failure behavior of steel dual-angle with cruciform welding filler plates (DA-CWP) under compression. A total of three DA-CWP specimens were fabricated and tested under axial compression, where different slenderness ratios (i.e., 45, 60, 75) were considered for comparison. The failure performance was experimentally investigated from different perspectives, such as failure mode, ultimate capacity and strain development. Subsequently, numerical simulation was performed to further reveal the effect of slenderness ratio and filler plate type on the failure behavior of DA-CWP. Finally, A theoretical method to distinguish the compressive failure mode of DA-CWP was proposed, and the bending-torsion transition slenderness ratio calculated by theoretical method was compared with the one from simulation for verification. The results demonstrate that the failure mode of DA-CWP changes from torsion to bending as the slenderness ratio increases, gradually decreasing its ultimate capacity. Due to the lower torsion stiffness of steel dual-angle with alternate plates (DA-AP), the torsion instability is more prone to occur for DA-AP, resulting in larger deformations of DA-AP compared to DA-CWP under identical compression. The theoretical method proposed in this study provides a good prediction for the bending-torsion transition slenderness ratio of DA-CWP under axial compression, which can provide reference for ultimate capacity design.

Outcomes of late-stages infantile Blount's disease managed by acute single stage: medial hemi-plateau elevation and metaphyseal osteotomy. Eight case series.

This study aimed to evaluate the clinical and radiological outcomes of surgical intervention involving acute medial hemi-plateau elevation and metaphyseal osteotomy with internal fixation and growth modulation for late-stages Blount's disease. A retrospective analysis was conducted on consecutive patients with late-stages infantile tibia vara between 2014 and 2020. Inclusion criteria consisted of children aged 8 years and older with Blount's disease with Langenskiold stage IV, V or VI, tibia vara more than 30*, medial plateau depression angle (MPDA) exceeding 25* and knee instability with a minimum follow-up period of 3 years. Patients with Limb length discrepancy greater than 5 cm were excluded. Data collection included assessments of age, weight, disease stage, clinical tibiofemoral angle (TFA), mechanical medial proximal tibial angle (mMPTA), MPDA, tibial torsion and knee instability. Functional outcomes were evaluated using modified Pediatric Outcome Data Collection Instruments (PODCI) scores. The study included 5 children with 8 affected limbs. Among them, three children with five limbs had recurrent deformities after previous surgeries. All cases showed significant improvements in TFAs, mMPTA, tibial torsion, knee instability and modified PODCI scores. Complications included 4 cases of superficial infections, 1 intra-articular fracture, 2 minor screw breakage and 2 on-table under correction. Surgical intervention involving acute Single-stage medial hemi-plateau elevation and metaphyseal osteotomy leads to satisfactory outcomes in late-stages Blount's disease among older children. It is crucial to achieve proper correction of all deformity components during surgery, with epiphysiodesis on the lateral side to prevent further recurrence. Continuous follow-up until skeletal maturity is essential for optimal results.

Effect of Co- and Counterswirl Air on Swirl Airblast Atomization

For swirl-stabilized gas turbine combustor, liquid fuel distribution in the near field dictates local equivalence ratio, volumetric heat release, and heat transfer to the chamber wall, and hence its understanding is essential. The effect of inlet air aerodynamics on spray characteristics in a primary zone of a simulated gas turbine burner is studied using a phase Doppler particle analyzer, high-speed Mie scatter imaging, and an orthogonal decomposition method. By employing intense coswirl air, the luminous spray region shifts upstream to the burner exit, where lower mass flux can be observed in the central region and higher mass flux in the outer region of the spray due to the recirculation zone formation. Based on the size velocity joint probability distribution functions (JPDFs) and the individual droplet transport with acquisition time, we conclude that the recirculation zone entraps the smaller droplets and transports them from the downstream to the upstream spray region. Compared to coswirl, counterswirl air exhibits torsion instability, intensifies the concentration of drops in the central region, and improves secondary atomization. Finally, five distribution functions are curve-fitted to the experimental data to capture the atomization process accurately.

Modelling and analysis of fatigue physiological parameters of all tissues of football athletes under cervical vertebral stress based on biomechanical analysis

In the field of biomechanics, the study of cervical vertebrae injury has attracted much attention in recent years. Using the knowledge of biomechanics can help us to judge the stability of cervical spine after injury and understand its influencing factors. Through clinical observation on the curative effect of cervical spondylosis, the biomechanical effect and clinical value of treating cervical spondylosis and restoring the physiological curvature of cervical spine were preliminarily discussed. The results showed that the X-ray findings of 50 football athletes with cervical spondylosis in lateral position of cervical hyperextension and hyperflexion, left and right oblique position were analysed. Changes in cervical curvature, cervical rotation, vertebral angular displacement, and intervertebral slip were increased by an average of 20% under different physiological conditions. Studies have shown that football athletes' cervical curvature is straightened and the intervertebral activity is significantly reduced and redistributed. At the same time, the small joints and uncinate joints of the lower cervical vertebrae have a torsion instability state, which forms cervical instability and accelerates cervical degeneration.

Analysis of torsional instability and reliability of marine flexible pipelines

During the installation of marine flexible pipelines, components, such as flexible risers, umbilicals, and cables, subject to wave motion and ship yaw can cause torque on such pipelines. In addition, marine flexible pipelines are subjected to low tension at the touch down zone (TDZ), which could result in the torsion instability phenomenon of flexible pipeline in the TDZ, thus forming a loop. Moreover, when the tension on a marine flexible pipeline increases, the radius of the loop decreases and kinks can form, which could result in damage or fracture of the flexible pipeline, affecting its normal operation. In this study, the formation mechanism of a flexible pipeline loop is thoroughly analyzed considering the end torsion, tension, and environmental loads. The bending failure response surface function of the flexible pipeline is constructed considering the randomness of design parameters, e.g., elastic modulus, diameter, and density, and the probability of torsional instability of flexible pipeline is analyzed using both the first-order second moment and Monte Carlo simulation methods, both of which could give almost the same level of accuracy, while the first-order second moment method is computationally less expensive.

Tibial Torsion and Patellofemoral Pain and Instability in the Adult Population: Current Concept Review

Tibial torsion is a recognized cause of patellofemoral pain and instability in the paediatric population; however, it is commonly overlooked in the adult population. The aim of this review article is to summarize the current best evidence on tibial torsion for the adult orthopaedic surgeon. The true incidence of tibial torsion in the adult population is unknown, with significant geographical variations making assessment very difficult. CT currently remains the gold standard for quantitatively assessing the level of tibial torsion and allows assessment of any associated femoral and knee joint rotational anomalies. Surgical correction should only be considered after completion of a course of physiotherapy aimed at addressing the associated proximal and gluteal weakness. Tibial torsion greater than 30° is used as the main indicator for tibial de-rotation osteotomy by the majority of authors. In patients with associated abnormal femoral rotation, current evidence would suggest that a single-level correction of the tibia (if considered to be a dominant deformity) is sufficient in the majority of cases. Proximal de-rotational osteotomy has been more commonly reported in the adult population and confers the advantage of allowing simultaneous correction of patella alta or excessive tubercle lateralization. Previous surgery prior to de-rotational osteotomy is common; however, in patients with persistent symptoms surgical correction still provides significant benefit. Tibial torsion persists into adulthood and can play a significant role in patellofemoral pathology. A high index of suspicion is required in order to identify torsion clinically. Surgical correction is effective for both pain and instability, but results are inferior in patients with very high pain levels pre-surgery and multiple previous surgeries.

Stability Analysis of Arteries Under Torsion.

Vascular tortuosity may impede blood flow, occlude the lumen, and ultimately lead to ischemia or even infarction. Mechanical loads like blood pressure, axial force, and also torsion are key factors participating in this complex mechanobiological process. The available studies on arterial torsion instability followed computational or experimental approaches, yet single available theoretical study had modeled the artery as isotropic linear elastic. This paper aim is to validate a theoretical model of arterial torsion instability against experimental data. The artery is modeled as a single-layered, nonlinear, hyperelastic, anisotropic solid, with parameters calibrated from experiment. Linear bifurcation analysis is then performed to predict experimentally measured stability margins. Uncertainties in geometrical parameters and in measured mechanical response were considered. Also, the type of rate (incremental) boundary conditions (RBCs) impact on the results was examined (e.g., dead load, fluid pressure). The predicted critical torque and twist angle followed the experimentally measured trends. The closest prediction errors in the critical torque and twist rate were 22% and 67%, respectively. Using the different RBCs incurred differences of up to 50% difference within the model predictions. The present results suggest that the model may require further improvements. However, it offers an approach that can be used to predict allowable twist levels in surgical procedures (like anastomosis and grafting) and in the design of stents for arteries subjected to high torsion levels (like the femoropopliteal arteries). It may also be instructive in understanding biomechanical processes like arterial tortuosity, kinking, and coiling.

Torsion Instability of Anisotropic Cylindrical Tissues with Growth

Growth shapes soft tissues not only through mass addition or volume expansion but also through deformation instabilities and consequent morphological evolution. In this paper, we probe the torsion instability of an anisotropically growing tube with fiber reinforcement, which mimics many tubular organs in animals or plants. We derive the Stroh formulation for the incremental boundary value problem and numerically solve it using the surface impedance method. A linear stability analysis is conducted to investigate the critical condition for the onset of wrinkling. The thresholds of helical wrinkling are calculated in terms of growth ratio and external load. The effect of fibers on the critical state under axial stretching is examined. It is found that the tangential growth tends to enhance the critical torsion angle but has a weak influence on the critical longitudinal mode of wrinkling, which, however, can be remarkably affected by the axial growth. Our study can help understand the formation of helical morphologies in biological materials and provide cues for engineering desired structures or devices.

Voltage-induced torsion of a fiber-reinforced tubular dielectric elastomer actuator

A fiber-reinforced torsional dielectric elastomer (DE) actuator was conceived by embedding one family of helical fibers into a DE tube in the present work. Due to the constraint of the fibers, the application of an electrical voltage will induce torsional deformation which is coupled with the longitudinal and hoop stretches of the actuator. By employing an energy method, the voltage-induced torsion and snap-through instability of the DE tubular actuator were modeled and analyzed. Based on the formulation, the effects of the fiber stiffness and helical angle as well as externally applied mechanical loads on the voltage-induced torsional deformation were studied in detail. It was found that when snap-through instability occurs, the voltage-induced twist angle jumps from a smaller value in the unbulged state to a larger value in the budged state, and the voltage-induced twist angle can be effectively tuned by varying the fiber stiffness and helical angle. Moreover, the voltage-induced torsion of the actuator in the budged state is almost not affected by externally applied axial force or torque. The revealed results are expected to provide guide for the rational design and utilization of fiber-reinforced torsional DE actuators.

The Contribution of Different Femur Segments to Overall Femoral Torsion

Background: Femoral torsion is a critical parameter in hip and knee disorders. The unproven assumption is that the femoral neck exclusively contributes to the overall torsion of the femur. Purpose/Hypothesis: The aim of this study was to measure femoral torsion at different levels in patients with abnormally high or low femoral torsion and to compare the results with healthy volunteers. Our hypothesis was that the pattern of torsion distribution among the different femoral levels varies between patients with abnormal torsion and healthy volunteers. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Magnetic resonance images of patients with a history of patellar instability and torsion of the femur ≥25° (11 patients, 16 femurs) and ≤0° (14 patients, 22 femurs) were analyzed. Our controls were 30 healthy volunteers (60 femurs). To assess femoral torsion, 4 lines were drawn: a first line through the center of the femoral head and neck, a second line through the center of the femur at the top of the lesser trochanter, a third line tangent to the posterior aspect of the distal femur just above the attachment of the gastrocnemius, and a fourth line tangent to the posterior condyles. Three investigators performed the measurements; 1 performed the measurements twice. Results: All femur segments showed significantly different torsion among the high-torsion, low-torsion, and control groups. Regarding the pattern of torsion distribution, on average, all levels contributed to the torsion. The ratio between the average neck and shaft torsion shifted toward a higher value in the high-torsion group, mostly because of a lack of external torsion in the shaft, and toward a lower value in the low-torsion group, owing to both a lack of internal torsion of the neck and increased external torsion in the shaft. Conclusion: We established a difference between neck, mid, and distal femoral torsion with reproducible measurements. Our data suggest that all 3 levels of the femur contribute to the total femoral torsion, with a different pattern among patients with high torsion and patellar instability.

Torsion instability of soft solid cylinders

The application of pure torsion to a long and thin cylindrical rod is known to provoke a twisting instability, evolving from an initial kink to a knot. In the torsional parallel-plate rheometry of stubby cylinders, the geometrical constraints impose zero displacement of the axis of the cylinder, preventing the occurrence of such twisting instability. Under these experimental conditions, wrinkles occur on the cylinder's surface at a given critical angle of torsion. Here we investigate this subclass of elastic instability--which we call torsion instability--of soft cylinders subject to a combined finite axial stretch and torsion, by applying the theory of incremental elastic deformation superimposed on finite strains. We formulate the incremental boundary elastic problem in the Stroh differential form, and use the surface impedance method to build a robust numerical procedure for deriving the marginal stability curves. We present the results for a Mooney-Rivlin material and study the influence of the material parameters on the elastic bifurcation.

Total knee replacement with rotational proximal tibial osteotomy for osteoarthritis with severe external tibial torsion and patellar instability

The management of osteoarthritis of the knee associated with patellar instability secondary to external tibial torsion > 45 degrees is challenging. Patellofemoral biomechanics in these patients cannot be achieved by intra-articular correction using standard techniques of total knee replacement. We reviewed seven patients (eight knees) with recurrent patellar dislocation and one with bilateral irreducible lateral dislocation who had undergone simultaneous total knee replacement and internal tibial derotational osteotomy. All had osteoarthritis and severe external tibial torsion. The mean follow-up was for 47.2 months (24 to 120). The mean objective and functional Knee Society scores improved significantly (p = 0.0001) from 29.7 and 41.5 pre-operatively to 71.4 and 73.5 post-operatively, respectively. In all patients the osteotomies healed and patellar stability was restored. Excessive external tibial torsion should be identified and corrected in patients with osteoarthritis and patellar instability. Simultaneous internal rotation osteotomy of the tibia and total knee replacement is a technically demanding but effective treatment for such patients.

Infantile Blount's disease treated by hemiplateau elevation and epiphyseal distraction using a specific external fixator: preliminary report

The treatment of infantile Blount's disease remains controversial. The progressive development of epiphysiodesis of the medial tibial physis induced a complex deformity of the lower limb such as severe genu varum, joint incongruity, torsion instability and leg length discrepancy with major functional consequences. Nine knees on eight children (average age was 7 years and 2 months) were treated by a one-time procedure using a specific external fixator that combined elevation of the medial tibial plateau, axial correction in the valgus, complete sterilization of the upper tibial growth cartilage, leg lengthening anticipation and de-rotation if necessary. Magnetic resonance imaging was useful to describe the deformity and to prepare for surgery. Corrections were progressively obtained through the physis plan by means of short incisions and the use of a specific external fixator. The primary results at an average of 24 months were good with a low rate of complications but final evaluation will be conducted at the end of the children's growth period.