Flexion Resistance Research Articles

Clinical presentation of anterior pelvic tilt and trunk muscle endurance among patients with femoroacetabular impingement syndrome: a cross-sectional study.

Femoroacetabular impingement syndrome (FAIS) significantly affects the physical function and quality of life of the young and middle-aged population. Pelvic tilt and trunk muscle endurance are physical features poorly studied in FAIS. This study aimed to compare the anterior pelvic tilt and anterior, lateral, and posterior trunk muscles endurance between people with FAIS and healthy individuals, within FAIS sub types and between the symptomatic and asymptomatic hip in people with FAIS. Cross-sectional study. Participants were recruited and screened for potential eligibility at the Rehabilitation, Sports Medicine, and Physiotherapy Unit between April 2021 and February 2022. Sixty-nine patients with FAIS and 69 controls. A study adhering to STROBE guidelines recruited 138 participants (69 FAIS, 69 controls). The degree of pelvic tilt was measured by the palpation meter (PALM) tool. To assess trunk musculature endurance, isometric trunk tests described by McGill were performed (extension resistance test, flexion resistance test, and side plank test). Cases were classified based on FAIS subtypes. Differences between groups and subgroups were performed using t-tests and ANCOVA, respectively. Significant differences in anterior pelvic tilt were observed between the control and FAIS groups (P<0.001, d=0.72). Participants with FAIS exhibited greater pelvic tilt (MD=1.57, 95% CI=0.83 to 2.3). Trunk muscle endurance showed statistically significant differences (P<0.001, d=0.72) for posterior muscles. In comparisons between symptomatic and asymptomatic hips, significant differences were found in pelvic tilt (P<0.001, d=0.26) and lateral trunk muscle endurance (P<0.001, d=0.43). FAIS subtypes demonstrated significant differences in lateral trunk muscle endurance (P=0.002, η<inf>p</inf>2=0.209). This study found that patients with FAIS present large anterior pelvic tilt and lower posterior trunk muscle endurance. Although anterior pelvic tilt was comparable for all FAIS subtypes, Pincer-type with or without labral tear exhibited lower lateral trunk muscle endurance compared with Cam-type with or without labral tear. In addition, the symptomatic hip of FAIS patients showed lower lateral trunk muscle endurance compared to the asymptomatic hip. Incorporating rehabilitation strategies that address pelvic tilt and trunk muscle strengthening in individuals with FAIS might be considered as a potential means to improve these physical impairments, pending careful evaluation of their effectiveness.

Impact of plantar flexion resistive moment of dynamic ankle foot orthosis on measures of center of pressure and clinical gait outcomes in individuals with post-stroke hemiparesis

BackgroundAn ankle-foot orthosis (AFO) with plantar flexion resistance (PFR) can improve the first rocker function during gait, but the incremental changes in the resistive moment on balance and gait have not been well identified. ObjectivesTo investigate the effect of changing the PFR moment of dynamic AFO (DAFO) on measures of the center of pressure (COP) and clinical gait outcomes in individuals with post-stroke hemiparesis. MethodIn this randomized repeated measure study of 36 stroke individuals, the customized DAFO using foot drop ankle units set in three PFR situations (low, medium, and high) was evaluated. The balance parameters for COP measures were investigated by HUMAC® Balance & Tilt System. Gait parameters and ankle kinematics were recorded using the 3D motion analysis through force platform and optoelectronic system. The comparison was made using a parametric ANOVA test and the P value was set at 0.05 for statistical significance. ResultsSignificant differences were observed for COP average velocity (1.30 ± 0.64, 1.10 ± 0.05, and 1.37 ± 0.43), COP path length (43.3 ± 4.6, 33.4 ± 4.3, and 36.3 ± 5.4), walking velocity (11.0 ± 3.1, 13.2 ± 4.4, and 9.9 ± 3.5), and cadence (31.5 ± 2.0, 33.0 ± 3.1, and 29.0 ± 1.6) respectively for low, medium and high PFR settings (P < 0.05). Except for the COP path length and cadence, posthoc multiple comparisons revealed significant differences between low and medium (P < 0.05) and medium and high (P < 0.05) PFR grades. PFR with medium resistance demonstrated near-normal maximal peak ankle dorsiflexion (mean deviation of 8 degrees, P < 0.05). ConclusionMedium PFR grade should be encouraged since it can enhance balance parameters like path length and average velocity of COP, increase cadence and average velocity during gait, and improve maximal peak ankle dorsiflexion.

The effects of the quality of recycled aggregates on the mechanical properties of roller compacted concrete

This study investigates the performance of roller compacted concrete (RCC) made with recycled aggregates derived from crushed demolished concrete with various proportions of natural. The experimental study examines substituting various proportions of natural aggregate (3/8, 8/15, and 15/20) with recycled aggregate. The replacement rates range from 0% to 100% in increments of 25%. Eleven different mixtures have been made by changing the amount of recycled aggregate used, with and without pre-wetting, before being added to concrete. Additionally, 5% of the cement content was substituted with silica fume and slag in each composition. An experiment test was done to see how recycled aggregate-based BCRs' performance changed with the incorporation rate on fresh and hardened concrete's mechanical and physical properties. Physical parameters, including volume masse, vebe time consistency, and mechanical properties such as compression resistance, flexion resistance, and ultrasonic pulse speed, were measured over time. The results found were compared to the control mix made with 100% natural aggregates. Those results show that as the replacement rate increases, the water absorption rate increases with a decrease in mechanical strength. In addition, the pre-wetting treatment did not significantly impact mechanical strength. This can be explained by the characteristics of the recycled aggregate, such as high absorption, low resistance to wear, and low density, which were caused by the residual paste adhered to the recycled aggregate.

IMU- and TENS-based work and power calculation methods in hip flexion resistance training

Purpose: The study is the first part of a series presenting the primary results of multijoint hip flexion resistance training biomechanical investigation. The series evaluates the exercise in the context of possible implementation in hip flexors shortening and hypertension. The described exercise was designed to use muscle hypertrophy as a solution for pelvis stabilizing muscles’ imbalance. This study aims to evaluate the work performed and power generated during hip flexion resistance training using two established methods and investigate the potential of IMU sensors as a cost-effective tool for measuring individual performance and progress in non-laboratory settings. Methods: The study was conducted with the use of training equipment constructed according to patent P.435615 allowing for the application of downward directed force to feet while performing hip flexion. Thirteen healthy students (7 females and 6 males, body-height 176.00 ± 12.54 cm, body-mass 73.69 ± 18.08 kg, age: 21.77 ± 1.09 years) took part in the training session using three different additional loads (0, 2.5, and 5 kg). Techniques applied in the study included optical kinematics capture, strain gauges, and inertial sensors. Results: The average work of (TENS/IMU) were 56.57 ± 12.00 / 58.13 ± 13.07 - 76.54 ± 13.88 / 74.40 ± 13.93 J and an average power of 23.22 ± 6.43 / 23.65 ± 7.12 - 31.51 ± 9.42 / 31.62 ± 10.60 W were calculated for the additional load of 0 kg and 5 kg respectively. The correlation between values calculated with two tested methods was high both for power (R= .85 P&lt; .001) and work (R= .86 P&lt; .001). Conclusions: Referenced data indicate a good correlation between the two methods but prove the need for further improvement of IMU-based method precision. It also allowed to determine a potential baseline of 15kg additional load for 1RM tests maximal value.

Design and Evaluation of Hybrid Passive Spring Damper Ankle Foot Orthosis for Gait Performance in Drop Foot Patients: A Feasibility Study.

Passive and hybrid passive Ankle foot orthoses (AFOs) are the prevalent prescription in drop foot patients to prevent toe dragging during the swing phase. While, these AFOs have some limitations like inability to overcome foot slap, limitation in forward propulsion and inappropriate power generate at the push off. The aim of this study was to design a novel spring damper and evaluate the immediate effects of this AFO on improving the ankle kinetic and kinematic in drop foot patients. This AFO was generated from carbon composite frame and foot section with posterior hinge and spring damper actuator that controlled plantar flexion resistance at the early stance, freely dorsi flexion movement with the ability to store energy during mid-stance movement as well as restore this energy at the pre swing phase. This AFO was assessed on ten drop foot patients who used Posterior Leaf Spring AFO conditions and walked at their self-comfortable walking speed. Then the ankle kinetic and kinematic data in two conditions of with PLS (Posterior Leaf Spring) AFO, and novel spring damper AFO were assessed. Results showed a significant improve in the immediate effect of the kinetic and kinematic parameters. In conclusion, spring damper AFO improved all ankle angles in entire gait cycle as well as the ankle moments and power. Therefore, this AFO should be consider as a selective AFO in drop foot patients.

Effect of flexion-resist and extension-assist knee orthosis on electromyographic activities of quadriceps during lateral stepping.

Knee orthoses can potentially reduce muscular activities of the quadriceps. The aim of this study was to investigate the effect of a custom flexion-resist and extension-assist knee orthosis on electromyographic activities of quadriceps during lateral stepping (step-up and step-down). Flexion resistance and extension assistance mechanisms were set by a pair of linear springs built into the orthotic knee joints. Electromyography (EMG) signals were collected from rectus femoris (RF), vastus medialis obliquus (VMO), and vastus lateralis (VL) during lateral step-up and lateral step-down activities in 7 healthy young adults. Peak normalized root mean square (RMS) EMG signals of each muscle, as well as VMO:VL ratio, were compared between orthotic and nonorthotic conditions using the Wilcoxon signed-rank test. The knee orthosis significantly reduced the normalized RMS EMG signals of the RF and VL during lateral stepping ( p < 0.05). No significant difference was found in the VMO. The VMO:VL ratio significantly ( p < 0.05) increased under orthotic condition. The experiments demonstrated that the knee orthosis reduces the peak normalized RMS EMG signals of RF and VL, and alter the VMO:VL ratio of quadriceps in healthy young adults. Therefore, this study suggests that the flexion-resist and extension-assist knee orthosis may be effective in reducing muscular activities of RF and VL, which may alleviate patellofemoral loading. Future studies should delve into the effects of the knee orthosis in individuals with patellofemoral pain.

Serratus anterior dysfunction examination: wall push-up or shoulder flexion resistance test?

BackgroundWall push-up is the most common examination used for the diagnosis of scapular winging secondary to serratus anterior dysfunction. The wall push-up test (WPUT) however may not be able to differentiate causes of scapulothoracic abnormal motion (STAM) or winging. We introduce a novel physical examination maneuver, the shoulder flexion resistance test (SFRT), and we propose that this test is more specific and accurate in determining serratus anterior dysfunction as the cause of STAM.MethodsFifty patients with STAM are included in this study. All patients underwent clinical scapular examination using both WPUT and SFRT. The SFRT is performed by resisting shoulder flexion while the elbow is fully extended at 30°, 60°, and 100°. All patients additionally received preoperative electromyography. All patients underwent exploration and intraoperative stimulation of the distal serratus anterior to characterize color, thickness, and contractility at the time of their arthroscopic pectoralis minor release and scapulopexy or tendon transfer if the serratus was paralyzed. The preoperative clinical examination findings were then correlated with intraoperative findings.ResultsAbnormal distal serratus anterior was seen intraoperatively in 5/50 patients (10%) with marked alterations in color, thickness, and contractility. All (n = 50) patients had positive WPUT manifested by increased winging of the scapula off the chest wall (STAM) with 45 false positive tests. The WPUT was 100% (95% confidence interval [CI] 47.82%-100%) sensitive but 0% (95% CI 0%-7.87%) specific for lower serratus anterior deficiency. The SFRT was 100% sensitive (95% CI 47.82%-100%) and 100% specific (95% CI 92.13%-100%) for serratus anterior dysfunction as the cause of STAM. Using area under the curve (AUC) of receiver operating characteristic (ROC) curves for WPUT and SFRT tests, WPUT had clinically insignificant accuracy (AUC 0.5) compared to the excellent accuracy (AUC 1.0) of SFRT.ConclusionSFRT is specific and accurate in determining serratus anterior dysfunction as a cause of STAM. Based on this study, the SFRT should replace the WPUT as the physical exam of choice to determine dysfunction of the serratus anterior muscle and guide operative management of STAM.

The effects of ankle-foot orthoses with plantar flexion stop and plantar flexion resistance using rocker-sole shoes on stroke gait: A randomized-controlled trial.

Objectives This study aims to evaluate the effect of two ankle-foot orthoses (AFOs), AFO with plantar flexion stop (AFO-PlfS), and AFO with plantar flexion resistance (AFO-PlfR), while wearing standard shoes and rocker-sole shoes. Patients and methods Between November 2017 and July 2018, in this randomized-controlled study, a total of 20 stroke patients (8 males, 12 females; mean age: 48.1 years; range, 33 to 65 years) in chronic phase were randomized to AFO groups (AFO-PlfS group, n=10 and AFO-PlfR group, n=10). Each group received the allocated AFO along with two kinds of shoes (standard shoe and rocker shoe) for a two-week adaptation. Two effects were separately evaluated: The orthotic effect and rocker shoe effect were defined as the evaluation of using an AFO wearing standard shoe compared to only standard shoe, and evaluation of using an AFO wearing rocker shoe compared to an AFO wearing standard shoe, respectively. The gait of each group was measured by three-dimensional motion analysis. Results A significant orthotic effect was found in both AFO groups in spatiotemporal parameters and maximum ankle dorsiflexion in the single-support phase. Additionally, the AFO-PlfR group showed a significant improvement in the parameters related to the first rocker of gait, but not for AFO-PlfS group concerning the orthotic effect. The rocker shoe effect was found in significant reduction of peak ankle plantar flexor moment and power ankle generation during preswing for both AFO groups. Conclusion According to the orthotic effect, an AFO-PlfR can create better function in the improvement of parameters related to the first rocker. Although a rocker shoe can facilitate rollover for weight progression in the third rocker of gait, it cannot make a strong push-off function in stroke survivors.

High Compliance Pneumatic Actuators to Promote Finger Extension in Stroke Survivors.

Compliant pneumatic systems are well suited for wearable robotic applications. The actuators are lightweight, conformable to irregular shapes, and tolerant of uncontrolled degrees of freedom. These attributes are especially desirable for hand exoskeletons given their space and mass constraints. Creating active digit extension with these exoskeletons is especially critical for clinical populations such as stroke survivors who often have great difficulty opening their paretic hand. To achieve active digit extension with a soft actuator, we have created pneumatic chambers that lie along the palmar surface of the digits. These chambers can directly extend the digits when pressurized. We present a characterization of the extension force and passive flexion resistance generated by these pneumatic chambers across a range of joint angles as a function of cross-sectional shape, dimension, and wall thickness. The chambers were fabricated out of DragonSkin 20 using custom molds and were tested on a custom jig. Extension forces created at the end of the chamber (where fingertip contact would occur) exceeded 3.00 N at relatively low pressure (48.3 kPa). A rectangular cross-section generated higher extension force than a semi-obround cross-sectional shape. Extension force was significantly higher (p < 0.05) for actuators with the highest wall thickness compared to those with the thinnest walls. In comparison to previously used polyurethane actuators, the DragonSkin actuators had a much higher extension force for a similar passive bending resistance. Passive bending resistance of the chamber (simulating finger flexion) did not vary significantly with actuator shape, wall thickness, width, or depth. The flexion resistance, however, could be significantly reduced by applying a vacuum. These results provide guidance in designing pneumatic actuators for assisting finger extension and resisting unwanted flexion in the fingers.

Mechanical properties of an aluminium-carbon fiber composite for aircraft wing spar applications

Objective: The aim of this article is to solve the problem of wing spar flexibility of an aluminium drone aircraft. A 200 × 30 [mm × mm] aluminium sample weighing 32 g was collected corresponding to a density of 0.53 g/cm3, a bending load of 0.77 [kN] and a deflection of 45.54 mm. The goal is to increase flexion resistance and lightness. Methods: The following procedure was used to prepare the composite: a mold made up of two glass plates 250 mm long and 50 mm wide, gel-coated to prevent sticking. The mold was placed in a bag using vacuum bag technology by means of a refrigerator compressor. The bag was then heated at 80 °C for seven hours to prepare composites of acceptable quality and viscosity avoiding air bubbles and ensuring desired thickness. The first sample was prepared by inserting aluminium powder between four layers of glass fiber. In the second sample, the inserted layer was replaced by date pit powder. The third sample was prepared by placing four layers of glass fiber and two layers of carbon fiber in the lower layer and the upper layer. It was observed that aluminium powder inclusion resulted in better mechanical properties in comparison to date pit powder. Findings: However, the mechanical characteristics of the third sample were much better than those of the other samples. Based on these observations, the first and third samples were mixed to make the fourth sample in which four layers of glass fiber between each layer were used, placing the aluminium powder plus two layers of carbon fiber in the lower and upper layers with the aim of achieving the desired mechanical properties. The latter sample exhibited high strength and better curvature, high rigidity and corrosion resistance with the possibility of creating structures that are more integrated. These properties make the aluminium powder –carbon fiber based composite suitable for a drone aircraft wing spar. The obtained composite material prepared from glass fiber, aluminium powder, carbon fiber composed of four layers of glass fiber and aluminium powder between each layer and carbon fiber in the bottom layer and top layer exhibited has high strength, better bending, high stiffness and corrosion resistance with the possibility of creating more integrated structures. The prepared sample may outstand aluminium -based aircraft wing spar. Keywords Wing spar, bending, composite materials, aluminium­carbon fiber

Vantagens custo-efetivas da utilização de ureteroscópios flexíveis descartáveis em comparação com o uso de ureteroscópios flexíveis reprocessáveis

Objective: To analyze the cost-effectiveness of using disposable flexible ureteroscopes versus using reprocessable flexible ureteroscopes. Methods: Integrative literature review conducted in the SciELO, LILACS and MEDLINE databases, using the descriptors ureteroscopy, flexion resistance, marketing, cost-benefit analysis, and sterilization, whose object deals with the cost-effective advantages of using the flexible ureteroscope disposable. Results: Thirty-five articles were found and four were used in the study. In addition, characteristics of seven models of flexible ureteroscopes commercialized in Brazil, that are currently better known, were presented. The results were based on a joint analysis of the selected articles and characteristics of the flexible models presented, and discussed in two categories: the evolution of flexible ureteroscopes; and marketing mix - flexible single-use ureteroscopes. Conclusion: Despite the scarcity of research that deepens the costs of using a flexible single-use ureteroscope when compared to a reprocessable one, the benefits arising from the innovations added to these devices are notorious, giving a positive return both to the professional who uses it and to the patient, making it necessary to further analyze the possibility of migration from the “culture” of using flexible reprocessable ureteroscopes to disposable ones

Composites based on nylon 6/clinoptilolite by ultrasound-assisted extrusion for enhanced flame retardant and mechanical properties

Safe, lightweight, high-strength and sustainable materials are required for automotive parts and electrical components. In this paper, a polymeric composite based on nylon 6 and clinoptilolite (green fire retardant) was obtained by ultrasound-assisted extrusion. The materials were analyzed by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and cone calorimetry. From the FT-IR results, the presence of elements corresponding to the composition of the clinoptilolite that was used as an additive and nylon 6 was observed. TGA analysis showed that thermal stability improved, and in DSC analysis, we observed a slight increase in the crystallinity of the clinoptilolite polymer compounds, which was reflected in the flame retardation tests and by the mechanical properties. Significant improvement in the stiffness mechanical properties of nylon 6 with increasing clinoptilolite content was observed. For clinoptilolite contents of 1, 5 and 10% weight, the Young’s modulus increased by 3352.79, 3675.53 and 4327.06 MPa, respectively, compared to that of nylon 6, with a value of 2997.45 MPa. Meanwhile, the flexion resistance of nylon 6 increased from 84.75 to 95.05, 99.9 and 105.4 N/mm2 for the compounds obtained. The homogeneous distribution of clinoptilolite in the polymeric matrix due to processing by ultrasonic-assisted melt extrusion prevents the formation of stress concentration points. Flame retardant properties were studied with cone calorimetry, and a reduction in the peak heat release rate (HRR) was observed.

Knee Swing Phase Flexion Resistance Affects Several Key Features of Leg Swing Important to Safe Transfemoral Prosthetic Gait.

We systematically investigate in-vivo the effect of increasing prosthetic knee flexion damping on key features of the swing phase of individuals with transfemoral amputation during walking. Five experienced prosthesis users walked using a prototype device in a motion capture laboratory. A range of interchangeable hydraulic rotary dampers was used to progressively modify swing phase flexion resistance in isolation. Toe clearance (TC; vertical distance toe to floor), effective leg length (ELL; distance hip to toe), and knee flexion angle during swing phase were computed, alongside the sensitivities of vertical toe position to angular displacements at the hip, knee and ankle. Key features of these profiles were compared across 5 damping conditions. With higher damping, knee extension occurred earlier in swing phase, promoting greater symmetry. However, with implications for toe catch, minimum TC reduced, and minimum TC and maximum ELL occurred earlier; temporally closer to mid-swing, when the limb must pass the stance limb. Further, TC became less sensitive to changes in hip flexion, suggesting a lesser ability to control toe clearance without employing proximal or contralateralcompensations.Thereisatrade-offbetweenkeyfeaturesrelated to gait safety when selecting an appropriate resistance for a mechanical prosthetic knee. In addition to highlighting broader implications surrounding swing phase damping selection for the optimization of mechanical knees, this work reveals design considerations that may be of utility in the formulation of control strategies for computerized devices.

PHYSICAL-MECHANICAL CHARACTERIZATION OF THE WOOD OF Plathymenia reticulata BENTH (VINEYARD-OF-FIELD) NATIVE SPECIES OF THE CERRADO OF THE STATE OF TOCANTINS

Physical-Mechanical Characterization of the Wood of Plathymenia reticulata Benth (Vinhático-do-campo) Species of the Cerrado Biome of the State of Tocantins. The objective of this work was to determine the physical and mechanical properties of Plathymenia reticulata Benth (vinhático-do-campo) wood to indicate its potential use. The wood used in the production of the specimens came from the municipality of Dueré – TO native forest. The basic density, wood retractability, and anisotropy coefficient were obtained from physical tests, and the values of axial compression and static flexion resistance from the mechanical tests. The values obtained showed that the Plathymenia reticulata Benth wood fits the C40 resistance classification for hardwoods, determined by the Brazilian Standard (NBR7190). The average value of the basic density found was 0.64 g cm-3, classified as a medium density wood and the values of tangential, radial and volumetric retractability were 6.11%, 3.06%, 9.39 %, respectively. As for its mechanical characteristics, it presented average values of compressive strength parallel to the fibers, resistance to static flexion, and elastic modulus equal to 58.8MPa, 128.2 MPa, and 12760.0MPa, respectively. The vinhático-do-campo wood can be classified as stable wood and its physical characteristics suggest a normal quality. The species can be applied in light and heavy construction.

Coffee Husk as Feldspar Substitute in the Manufacture of Enameled Ceramic Tile

This study researches the effect of adding coffee husk (CH) and coffee husk ash (CHA) as partial feldspar substitutes to the manufacture of enameled ceramic tiles. Clays and other paste additives were characterized using XRD and XRF. The designed prototypes were pressed, dried, and fired at 1,120 °C. The physical (drying and firing shrinkage, apparent density, water absorption) and mechanical (flexion resistance) properties were evaluated and compared with standard fired specimens. Although the physical and mechanical properties of the specimens with 5 and 10 % CH and CHA make them suitable for the manufacture of BIIb ceramic tiles, it was concluded that CH and CHA under the working conditions do not replace feldspar in the preparation of enameled ceramic tiles due to surface quality defects.

Changes in muscular and postural control after proprioceptive focal stimulation with Equistasi® device in middle-moderate Parkinson’s disease

Fractures of the odontoid present frequently in spinal trauma, and Type II odontoid fractures, occurring at the junction of the odontoid process and C2 vertebrae, represent the bulk of all traumatic odontoid fractures. It is currently unclear what soft-tissue stabilizers contribute to upper cervical motion in the setting of a Type II odontoid fracture, and evaluation of how concomitant injury contributes to cervical stability may inform surgical decision-making as well as allow for the creation of future, accurate, biomechanical models of the upper cervical spine. The objective of the current study was to determine the contribution of soft-tissue stabilizers in the upper cervical spine following a Type II odontoid fracture. Eight cadaveric C0-C2 specimens were evaluated using a robotic testing system with motion tracking. The unilateral facet capsule (UFC) and anterior longitudinal ligament (ALL) were serially resected to determine their biomechanical role following odontoid fracture. Range of motion (ROM) and moment at the end of intact specimen replay were the primary outcomes. We determined that fracture of the odontoid significantly increases motion and decreases resistance to intact motion for flexion–extension (FE), axial rotation (AR), and lateral bending (LB). Injury to the UFC increased AR by 3.2° and FE by 3.2°. ALL resection did not significantly increase ROM or decrease end-point moment. The UFC was determined to contribute to 19% of intact flexion resistance and 24% of intact AR resistance. Overall, we determined that Type II fracture of the odontoid is a significant biomechanical destabilizer and that concurrent injury to the UFC further increases upper cervical ROM and decreases resistance to motion in a cadaveric model of traumatic Type II odontoid fractures.

Reconstrução de dentes com retentores intrarradiculares: uma revisão da literatura

Objetivo: Realizar uma revisão da literatura sobre pinos intrarradiculares pré-fabricados de fibra de vidro. Metodologia: Foi realizada uma busca nas bases de dados PubMed e Google Scholar com os seguintes descritores: “Técnica para Retentor Intrarradicular”, “Tratamento” e “Falha de Restauração Dentária”. Resultados: Entre as vantagens dos sistemas intrarradiculares pré-fabricados pode-se destacar o baixo custo, simplicidade da técnica, conservação da estrutura dental remanescente, eliminação da fase laboratorial, e ainda, os pinos de fibra de carbono e vidro apresentam módulo de elasticidade semelhante ao da dentina e flexão similar à do dente o que reduz o risco de fraturas, quando comparados aos núcleos metálicos fundidos. Além disso, os pinos de fibra de vidro apresentam a vantagem de serem mais translúcidos, o que permite uma maior transmissão da luz, tornando-os mais estético. Conclusão: Os pinos de fibra de vidro são considerados, atualmente, a melhor opção para tratamento reabilitador de dentes tratados endodonticamente com extensa perda coronária, uma vez que, apresentam módulo de elasticidade semelhante ao da dentina, resistência à flexão, simplicidade da técnica, menor tempo clínico e apresentam estética superior aos demais pinos intrarradiculares.

Loads distributed in vivo among vertebrae, muscles, spinal ligaments, and intervertebral discs in a passively flexed lumbar spine.

The load distribution among lumbar spinal structures-still an unanswered question-has been in the focus of this hybrid experimental and simulation study. First, the overall passive resistive torque-angle characteristics of healthy subjects' lumbar spines during flexion-extension cycles in the sagittal plane were determined experimentally by use of a custom-made trunk-bending machine. Second, a forward dynamic computer model of the human body that incorporates a detailed lumbar spine was used to (1) simulate the human-machine interaction in accordance with the experiments and (2) validate the modeled properties of the load-bearing structures. Third, the computer model was used to predict the load distribution in the experimental situation among the implemented lumbar spine structures: muscle-tendon units, ligaments, intervertebral discs, and facet joints. Nine female and 10 male volunteers were investigated. Lumbar kinematics were measured with a marker-based infrared device. The lumbar flexion resistance was measured by the trunk-bending machine through strain gauges on the axes of the machine's torque motors. Any lumbar muscle activity was excluded by simultaneous sEMG monitoring. A mathematical model was used to describe the nonlinear flexion characteristics. The subsequent extension branch of a flexion-extension torque-angle characteristic could be significantly distinguished from its flexion branch by the zero-torque lordosis angle shifted to lower values. A side finding was that the model values of ligament and passive muscle stiffnesses, extracted from well-established literature sources, had to be distinctly reduced in order to approach our measured overall lumbar stiffness values. Even after such parameter adjustment, the computer model still predicts too stiff lumbar spines in most cases in comparison with experimental data. A review of literature data reveals a deficient documentation of anatomical and mechanical parameters of spinal ligaments. For instance, rest lengths of ligaments-a very sensitive parameter for simulations-and cross-sectional areas turned out to be documented at best incompletely. Yet by now, our model well reproduces the literature data of measured pressure values within the lumbar disc at level L4/5. Stretch of the lumbar dorsal (passive) muscle and ligament structures as an inescapable response to flexion can fully explain the pressure values in the lumbar disc. Any further external forces like gravity, or any muscle activities, further increase the compressive load on a vertebral disc. The impact of daily or sportive movements on the loads of the spinal structures other than the disc cannot be predicted ad hoc, because, for example, the load distribution itself crucially determines the structures' current lever arms. In summary, compressive loads on the vertebral discs are not the major determinants, and very likely also not the key indicators, of the load scenario in the lumbar spine. All other structures should be considered at least equally relevant in the future. Likewise, load indicators other than disc compression are advisable to turn attention to. Further, lumbar flexion is a self-contained factor of lumbar load. It may be worthwhile, to take more consciously care of trunk flexion during daily activities, for instance, regarding long-term effects like lasting repetitive flexions or sedentary postures.

Application of hazardous serpentine rocks’ extraction wastes in composites with glass waste and clay-sand mix to produce environmentally clean construction materials

The objective of this research is to develop new ceramic materials using hazardous serpentine asbestos extraction dust waste (45–70 wt%), clay-sand mix (30–50%) and glass waste (0–5%). The raw materials and ceramics were characterized by XRD, XRF, SEM/EDS and LAMMA analyses. The ceramic bodies were formed by axial pressing, drying and sintering in an electric oven at temperatures of 950°, 1000°, 1050°, 1100°, 1150°, 1200°, 1250° and 1300 °C. The flexion resistance values of the ceramics varied in the range of 2.85–56.97 MPa, the water absorption rate ranged from 0.28 to 17.61% and linear shrinkage, between 5.80 and 11.66%. These values of the mechanical properties were achieved due to the chemical interaction of the raw materials and syntheses of mainly glass formations with inclusions of enstatite and forsterite. Using the present findings at the industrial level will provide an opportunity to solve a serious ecological problem of serpentine dust wastes contamination, to recover the ecological situation in the areas of serpentine mining and to avoid the accumulation of serpentine wastes.

Effects of Different Combinations of Concentric and Eccentric Resistance Training Programs on Traditional and Alternative Hamstrings-to-Quadriceps Ratios.

Resistance training is often recommended for combined increases in traditional and alternative hamstrings-to-quadriceps (H:Q) ratios in order to reduce knee strength imbalance and associated hamstrings and knee ligament injury risk. The aim of this study was to investigate the effect of different concentric and eccentric resistance training programs on traditional and alternative H:Q ratios. Forty male volunteers were assigned to one of 4 groups: concentric quadriceps and concentric hamstrings (CON/CON, n = 10), eccentric quadriceps and eccentric hamstrings (ECC/ECC, n = 10), concentric quadriceps and eccentric hamstrings (CON/ECC, n = 10), or no training (control (CNTRL), n = 10). Traditional conventional (CR) and functional (FR), alternative rate of torque development (RTD), muscle size (MS), and muscle activation (MA) H:Q ratios were measured before and after six weeks of unilateral nondominant knee extension–flexion resistance training performed on an isokinetic dynamometer. The ECC/ECC training significantly increased FR (pre = 0.75 ± 0.11; post = 0.85 ± 0.15), whereas the lack of training (CNTRL) decreased the RTD H:Q ratio (pre = 1.10 ± 0.67; post = 0.73 ± 0.33). There were no differences between groups for the other traditional and alternative ratios following resistance training protocols. These findings suggest eccentric exercise for quadriceps and hamstrings as the most beneficial training program for inducing increases in the traditional FR. However, different resistance training strategies may be needed to also elicit increases in the alternative RTD, MS, and MA H:Q ratios for fully restoring muscle balance and reducing potential hamstrings and knee ligament injury risk.