Moment Rotation Research Articles

Deformation and Fracture Mechanisms of Thick Hard Roofs in Upward Mining Coalfaces: A Mechanical Model and Its Validation

The safety and efficiency of underground coal mining are threatened by thick hard roofs characterized by large overhang areas, problematic spontaneous caving, and high dynamic load upon their breakage. In this study, a mechanical model of the bearing capacity of thick hard roofs in upward mining coalfaces associated with mining activities is built based on bending theories for beams with single generalized displacement and the elastic foundation beam theory. Using this method, we analyze the deformation and fracture mechanisms of a thick hard roof during upward mining. We further derive the mechanical equations of rotational angle, bending moment, shear force, and deflection of the free overhang and coal-bearing zone in the thick hard roof and an equation for calculating the limiting span. The mechanical behaviors of the thick hard roof bearing state are analyzed under different parameters. The results show that the foundation coefficient, roof thickness, and angle of upward mining have little influence on the roof bending moment but are positively correlated to the limiting span. Roof load and overhang length have a significant influence on the roof bending moment. They are negatively and positively correlated with the limiting span, respectively. Finally, a case study is performed on the Ш601 upward mining coalface in the Zhuzhuang Coal Mine. The distribution characteristics of the bending moment of the thick hard roof at different extraction stages are analyzed. At each stage, the limiting spans of the thick hard roof upon breaking were calculated as 13.18, 18.82, and 22.50 m, respectively, being close to the on-site measured periodic weighting lengths of 13.33, 19.33 m, and 22.67 m. This close fit proves the feasibility and accuracy of the developed mechanical model. The present study offers theoretical guidance for estimating the weighting length of thick hard roofs in coalfaces and for engineering technology control in similar scenarios.

Evaluation of a time-varying cut-off frequency low-pass filter for assessing knee joint moments and ACL injury risk

ABSTRACT Conventional low-pass filtering of 3D motion capture signals prior to estimating knee joint moments and ACL injury risk has known limitations. This study aimed to evaluate the fractional Fourier filter (FrFF), which employs a time-varying cut-off frequency, for assessing peak knee moments during common ACL injury risk screening tasks. Ground reaction force and motion data were collected from 23 team sport athletes performing 45° unanticipated sidesteps and drop jumps. Peak knee abduction, internal rotation and non-sagittal moments were estimated using inverse dynamics after five different low-pass filter approaches were applied (FrFF vs. four variations of a fourth-order Butterworth filter). The FrFF produced peak knee moments larger than “matched” (i.e. force and motion cut-off frequencies were equivalent) and closer to “unmatched” (i.e. force and motion cut-offs were different) Butterworth filter approaches and removed problems with representing foot-to-ground impact peaks. Participants with larger peak moments were identified as “at risk” of injury irrespective of filter approach, but the FrFF identified “at risk” classifications conventional approaches did not. Preliminary evidence suggests that the FrFF displays enhanced sensitivity to movement strategies that induce high knee loads. This was most evident for sidestepping, with more research warranted to optimise the FrFF for drop jumps.

Determination of the moment–rotation relation of continuous timber–concrete composite floors based on the component method

Timber–concrete composite (TCC) combines the advantages of timber and reinforced concrete construction. In multi-storey buildings, the design of TCC floors is often governed by the deformation serviceability requirements. One way to improve deformation serviceability is through the design of continuous floor systems. However, the current practice of TCC slab systems is often limited to load-carrying as single-span beams. This paper presents an analytical model based on the component method for determining the moment–rotation relation of continuous TCC slabs in the range with negative bending moments. The investigations involve the development of load–displacement curves for the individual force-transmitting components, including timber and reinforced concrete, followed by their assembly into a component model. The model has been verified using finite element calculations and the results demonstrate that the moment–rotation relation of continuous TCC systems can be accurately captured. As the variability of the material properties strongly influences the stiffness of the joint and therefore the deformation and stresses in the TCC slab, a probabilistic analysis of the material parameters was performed using the Monte Carlo method. The probabilistic investigations show that the variability of the input parameters has a significant impact on the joint stiffness, with notable scattering observed in the moment–rotation relation, especially in the range of the cracking phase of the concrete. The results from the probabilistic investigations enable initial statements about the joint stiffness of continuous timber–concrete composite slabs in ranges with negative bending moments.

Influence of Prophylactic Ankle Bracing on Knee Joint Moments and Ground Reaction Forces during Side-step Cutting Tasks

OBJECTIVES Prophylactic ankle bracing is widely used to prevent ankle sprains, but its effects on knee joint mechanics, particularly regarding ACL injury risk, are less understood. This study aimed to investigate the influence of ankle bracing on knee joint kinetics and ground reaction forces (GRFs) during a 90° side-step cutting task.METHODS Thirty physically active participants (15 males, 15 females) performed cutting trials under braced and unbraced conditions. Knee flexion, abduction, and internal rotation moments, along with mediolateral, anteroposterior, and vertical GRFs, were measured using a motion analysis system and a force plate. Paired t tests were conducted to compare the knee joint moments and GRFs between the two conditions.RESULTS The results showed that while ankle bracing did not significantly affect GRFs, it significantly increased knee internal rotation moment (<i>p</i> = 0.003). No significant differences were observed in knee flexion or abduction moments.CONCLUSIONS Ankle bracing, though beneficial for ankle stability, may elevate the risk of ACL injuries during dynamic activities like cutting by increasing knee internal rotation moments. Clinicians and coaches should weigh the benefits of ankle bracing against potential risks to knee health and consider alternative injury prevention strategies focused on neuromuscular control and strength training.

Kinetic and kinematic strategies integrating the trunk and lower limbs for a powerful soccer kick in amateur players

ABSTRACT This study investigated the kinematic (KmS) and kinetic (KnS) strategies integrating the trunk and lower limbs to achieve maximal kicking performance. Although strategies consisting of individual joint movements or moments are known, strategies combining joint movements or moments of the trunk and lower limbs have been less studied. Fifty adult amateur soccer players were assessed. Peak joint angles and moments of the trunk, the hip of the supporting limb, the hip and knee of the kicking limb, and the velocities of the foot and ball were recorded. Canonical Correlation Analysis evaluated relationships between sets of variables. A combination of greater hip extension and knee flexion of the kicking limb, as a KmS, correlated with better kick performance (Rc = 0.60, p = 0.004). Furthermore, a combination of larger moments of trunk flexion and rotation, internal rotation of the supporting hip, hip flexion, and knee extension of the kicking limb, as a KnS, were associated with better performance (Rc = 0.74, p < 0.001). The explained variance was 43% for the KmS and 59% for the KnS. In amateur players, the KmS for better kick performance involved greater hip and knee movement of the kicking limb, while the KnS involved greater moments at the trunk and both lower limbs.

Gait analysis and clinical outcomes of anterior and lateral approach total hip arthroplasty: A prospective randomized study

Objectives: This study compared the lateral and direct anterior approaches (DAAs) for total hip arthroplasty (THA) regarding gait analysis and post-operative outcomes. Methods: Patients undergoing THA for osteonecrosis or primary osteoarthritis were randomized to either the lateral or DAA. Standardized surgical procedures and implants were used. Gait analysis, including temporal distance parameters, kinetics, and kinematics, was conducted at 6 weeks, 3 months, and 18 months. Results: Thirty-four patients (16 lateral, 18 anterior) participated, with comparable demographics. At 6 weeks, the anterior approach group had significantly higher Harris hip scores, improved gait speed, greater hip extension and external rotation moments, higher peak hip abduction angle, and reduced peak hip extension angle. The lateral approach (LA) group showed decreased hip abduction and internal rotation moments. By 3 and 18 months, outcomes were similar between groups. Conclusion: The anterior approach facilitates faster rehabilitation at 6 weeks, but outcomes converge with the LA by 3 and 18 months postoperatively.

A novel four parameter formula for the rotational spectra of even-even nuclei

In this article, the authors presents a novel four parameter formula based on developing an expression for the moment of inertia in terms of Bohr-Mottelson Geometric Collective Model (GCM). The formula provides an excellent agreement with the experimental data for all nuclei under consideration. Some key quantities will also be derived such as the rotational frequency, the kinematic and dynamical moment of inertia, and their variation with spin will be investigated. A comparison between our proposed four parameter model with both the variable moment of inertia model, and the recently proposed β-stretching model is also presented. Various ΔI=1 and ΔI=2 energy staggering indices will be presented and compared to the experimental counterpart in the paper.

Effectiveness of Injury Prevention Program Using a Global Systems Approach on High-Risk Movement Mechanics for Noncontact ACL Injury.

Injury prevention training using a global systems approach was designed to develop integrated trunk-lower extremity neuromuscular control using whole-body, rotational forces about the vertical Z-axis during simulated sports movements. Compared with traditional hip-focused exercises, injury prevention training using a global systems approach could improve kinetic and kinematic measures related to anterior cruciate ligament injury. Controlled laboratory study. Level 3. A total of 39 male and female athletes received 6 weeks of either global systems approach (n = 20), or hip-focused strengthening, balance, and plyometrics training (n = 19) exercises. Before and after the training program, participants performed a single-leg vertical drop jump task on their dominant leg. Peak vertical ground-reaction forces (GRFs), peak knee abduction, internal rotation moments, peak hip flexion, hip adduction, knee flexion, knee abduction, contralateral pelvic drop, and lateral trunk flexion angles were assessed. Biomechanical data were compared between the 2 groups using a random-intercept linear mixed-models analysis. A significant group × time interaction effect was found for vertical GRFs (P = 0.01; change difference relative to baseline: 4.5%), knee abduction moment (P = 0.01; 14.8%), hip adduction (P < 0.01; 16.7%), knee abduction (P < 0.01; 13.8%), contralateral pelvic drop (P < 0.01; change difference: 26.6%), and lateral trunk flexion (P = 0.04; 20.37%) angles, favoring the global systems approach group after 6 weeks of training. Participants who trained using the global systems approach had significantly decreased lateral trunk flexion, hip adduction, knee abduction and contralateral pelvic drop angles, peak vertical GRFs, and peak knee abduction moment during a single-leg vertical drop jump compared with participants who trained with hip-focused exercises. Incorporating additional external resistance at the proximal trunk results in improved biomechanics compared with conventional hip-focused exercises.

Is the Frequency of a Targeted Neuromuscular Training Program a Factor in Modifying Knee Joint Loading During Typical Netball Landing Tasks?

Unplanned sidestep cutting and forward single-leg jump-landing contribute to non-contact anterior cruciate ligament (ACL) injuries in netball. Neuromuscular training programs (NMTPs) have shown promising results in reducing injury risk in certain populations when compliance is high. Compliance is easier to achieve when NMTPs are effective yet require minimal time for completion. Once- and thrice-weekly intervention groups would be equally effective in reducing knee abduction and internal rotation moments during forward single-leg jump landing and unplanned sidestep cutting. Randomized controlled trial. Level 3. External peak knee abduction and peak knee internal rotation moments during unplanned sidestep cutting and forward single-leg jump-landing were assessed pre- and post-intervention for 17 elite-level female netballers assigned randomly to either a once-weekly or thrice-weekly group. Regular netball training continued throughout the intervention, which lasted 6 weeks (30 minutes/session). One-way analysis of covariance (α = 0.05) was utilized to compare post-intervention peak knee abduction and peak knee internal rotation moments between groups, controlling for pre-intervention knee moments during the forward single-leg jump-landing and unplanned sidestep cut. Paired t tests were used to examine within-group changes in knee moments pre- versus post-intervention. For unplanned sidestep cuts on the right leg, both groups differed significantly, with the once-weekly group displaying a decrease in peak knee internal rotation moments [F(1,14) = 5.23; P = 0.04] whereas the thrice-weekly group did not. No other significant group interactions were found. A condensed NMTP with targeted exercises, performed once-weekly as part of regular training, shows potential to reduce peak knee internal rotation moments that are injurious to the ACL during unplanned sidestep cutting in adult female netballers. A once-weekly targeted NMTP would pose minimal disruption to a high-performing athlete's training schedule and likely increase compliance to ensure the success of the NMTP.

Dynamic model and characteristic analysis of a combined algebraic spiral scroll compressor

The combined algebraic spiral (CAS) effectively maximizes the geometric performance of a scroll compressor; however, its dynamic behavior remains inadequately explored. Utilizing the geometric model of the CAS scroll compressor, this study derived the functional relationship between the meshing point and the rotation angle, and calculated the working chamber volume using the discrete Green's theorem method. A dynamic model of the CAS scroll compressor was developed, and the influence of various parameters on its dynamic characteristics was analyzed. The findings indicate that when the polar angle interval is less than 0.01π, the discrete Green's theorem method accurately computes the working chamber volume. Among the gas forces acting on the CAS scroll compressor, the axial gas force is the most significant, followed by the tangential gas force, while the radial gas force is considerably smaller. The tangential gas force predominantly influences the overturning and rotational moments. Notably, when the polar angles of the connection points between the higher-order curve and the starting and ending algebraic spirals are set at 1.5π and 3π, the gas force remains low while maintaining geometric performance. This configuration results in reduced variation in gas force and enhanced dynamic performance. The spiral coefficient and spiral index of the starting algebraic spiral should be set as intermediate values to ensure optimal geometric and dynamic performance of the CAS scroll compressor.

Residual Performance and Biomechanical Asymmetries During Jumping Tasks in Female Athletes at 9 Months After Anterior Cruciate Ligament Reconstruction.

Biomechanics and anterior cruciate ligament injury mechanisms differ in males and females. There is a need for more data on between-limb biomechanical differences after anterior cruciate ligament reconstruction (ACLR) in females. To explore biomechanical asymmetries throughout the kinetic chain during the single-legged (SL) and double-legged (DL) countermovement jump (CMJ) and drop jump (DJ) in female athletes after ACLR. Descriptive laboratory study. Kinematic and kinetic between-limb differences were analyzed during the SL and DL CMJ and DJ in 67 female athletes 9 months after ACLR. Biomechanical and performance asymmetries between limbs during the jumps and isokinetic strength testing were analyzed with statistical parametric mapping. The entire stance phase was used for the paired t tests of the biomechanical variables, with Cohen d effect sizes of significant portions of the stance phase (reported as % of stance) calculated in a point-by-point manner. Decreased vertical ground-reaction force, internal knee abduction moment, knee internal rotation angle, hip external rotation angle, internal ankle eversion, and external rotation moments were seen in the ACLR limb during all 4 vertical jump tests. The greatest number and highest value of differences were found during the DLDJ, with asymmetries having medium to large effect sizes. They tended to appear more frequently in the concentric phase (50% to 100% of stance) during the SLCMJ and DLCMJ and in the eccentric (0% to 49% of stance) and concentric (50% to 100% of stance) phase during the SLDJ and DLDJ. For the SLCMJ, SLDJ, and quadriceps strength, performance asymmetries of >15% were detected but not for change of direction. The findings suggest that return-to-play testing in female athletes should examine the entire stance phase and include assessments of kinetic and kinematic variables throughout the kinetic chain. Greater deficits were highlighted in the DJ than in the CMJ, and greater performance asymmetries were evident in the SL tasks, with greater kinetic and kinematic and compensatory strategies evident in the DL tests. Biomechanical analysis focusing on contralateral compensation strategies and sex-specific interventions are necessary before return to play.

Analytical models for predicting the moment‒rotation relationships of steel hub joints with bolted steel side plates in single-layer wood reticulated domes

A very popular and efficient pattern of joints adopted for wood reticulated domes is steel hub joints featuring end-bearing and bolt-connected wood members (EBBC joints). This type of joint shows clear semi-rigidity, which affects the rigidity and overall stability of the structures. This study developed analytical models for predicting the moment‒rotation curves of EBBC joints, considering the effect of axial compression. Specifically, two models termed the WR and WEP models, were developed assuming rigid and elastic-plastic constitutive behaviour, respectively, of the wood in the compression zone of the joint. A tri-linear model for the lateral force-slip relationship of bolt connections was derived. A formula for calculating the deformation modulus and predicting the shear failure of wood members under local compression was proposed and verified. The moment–rotation relationship of the joint was established with equilibrium and compatibility conditions. The accuracy of the analytical models was verified by comparison with a series of experimental results as well as the parametric study results obtained using a refined finite element model. It was revealed that both the WR and the WEP models can predict the moment–rotation relationships accurately for joints without axial compression, whereas for the case of non-negligible axial compression loads, the WEP model offers more accurate predictions. The analytical WEP model proposed in the current paper provides a versatile tool for general design practice to predict moment–rotation curves for traditional or novel EBBC joints.

Toward 3D magnetic force microscopy: Simultaneous torsional cantilever excitation to access a second, orthogonal stray field component

Magnetic force microscopy (MFM) is long established as a powerful tool for probing the local stray fields of magnetic nanostructures across a range of temperatures and applied stimuli. A major drawback of the technique, however, is that the detection of stray fields emanating from a sample’s surface rely on a uniaxial vertical cantilever oscillation, and thus are only sensitive to vertically oriented stray field components. The last two decades have shown an ever-increasing literature fascination for exotic topological windings where particular attention to in-plane magnetic moment rotation is highly valuable when identifying and understanding such systems. Here, we present a method of detecting in-plane magnetic stray field components, by utilizing a split-electrode excitation piezo that allows the simultaneous excitation of a cantilever at its fundamental flexural and torsional modes. This allows for the joint acquisition of traditional vertical mode images and a lateral MFM where the tip–cantilever system is only sensitive to stray fields acting perpendicular to the torsional axis of the cantilever.

The influence of knee position during static calibration trials on evaluation of knee loading during gait in individual with medial knee osteoarthritis

Quantitative three-dimensional gait analysis has been used to evaluate the loading at the knee (i.e. external knee adduction moment, EKAM) during level ground walking in individuals with knee osteoarthritis (OA). The magnitude of EKAM can be influenced by some factors, such as knee marker position and foot placement angles in static calibration trials, which may lead to inaccurate functional assessments and intervention planning. This study aimed to clarify the effects of knee position during static calibration trials on the evaluation of knee loading during gait in individuals with medial knee OA. Seventeen individuals with medial knee OA completed three different static standing trials; (1) knee flexed at 0 degrees, (2) knee flexed at 15 degrees, and (3) knee flexed at 30 degrees before walking at their self-selected speed. A sixteen-camera three-dimensional VICON gait analysis system with four AMTI force platforms was used to collect the EKAM, knee adduction angular impulse (KAAI), knee joint center (KJC), and other knee kinematic and kinetic variables during gait. A repeated measures ANOVA was used to investigate the differences between conditions. The 1st peak of EKAM, the 1st peak EKAM arm, KAAI, and knee extension moment were significantly increased at the 15-degree and 30-degree conditions in comparison with the 0-degree condition (P < 0.05). Additionally, the knee flexion moment and knee external rotation moment were significantly reduced at the 15-degree and 30-degree conditions in comparison with the 0-degree condition (P < 0.05). All biomechanical variables were influenced by the localization of the KJC during static calibration trials. The changes in knee position during static trials significantly affected the 1st peak EKAM, KAAI, and other knee kinematics and kinetics variables during gait. Therefore, future studies should consider keeping the participants’ knees in a consistent position during static trials between visits, as the variations in knee position could mask or exaggerate the differences between groups and interventions.

Dynamic Modeling and Behavior of Cylindrical Roller Bearings Considering Roller Skew and the Influence of Eccentric Load

At high speeds, skew and skid may frequently occur for the rollers in cylindrical roller bearings, especially when under eccentric load, as the uneven load distribution along the generatrix of the roller further aggravates this phenomenon. In this paper, a dynamic model of a cylindrical roller bearing was established, taking into account roller skewing and interactions with the cage. Firstly, the interaction between the roller and the raceway was calculated by slicing the roller along its generatrix. Furthermore, the computation of the interaction between the roller and the cage is based on elastic theory, taking into account pocket clearance. Subsequently, the dynamic equations for both rollers and cage were derived. Based on this foundation, an investigation was conducted to reveal how rotational speed, radial loads, and moment loads affect roller slipping, skewing characteristics, and interactions with the cage under uneven load conditions. The findings indicate a direct proportionality between roller slipping and bearing speed while exhibiting an inverse relationship with load magnitude. Additionally, it was observed that both bearing speed and load have a direct influence on roller skewing angle. Moreover, normal interaction force between the roller and cage demonstrates a direct proportionality to bearing speed while inversely correlating with load magnitude.

Neutron stars in f(R,T) theory: slow rotation approximation

In this paper, we study the slowly rotating neutron stars in f(R, T) gravity based on Hartle-Thorne formalism. We first consider the simplest matter-geometry coupled modified gravity, namely f(R, T) = R + 2χ T. We compute the mass, radius, moment of inertia, change in radius, and binding energy due to rotation, eccentricity, quadrupole moment, and the tidal love number. The quantities, which are of the second order in angular velocity, like change in radius and binding energy due to rotation, eccentricity, and quadrupole moment, deviate more from their corresponding general relativistic counterparts in lighter neutron stars than heavier ones. Whereas the moment of inertia, which is of the first order in angular velocity, in f(R, T) = R + 2χ T modified gravity, barely diverges from the general relativistic one. The Equation of state-independent I-Love-Q relation retains in this f(R, T) modified gravity, and it coincides with the general relativistic ones within less than one percent even for the maximum allowed coupling parameters. We also study the slowly rotating neutron star in f(R, T) = R + αR 2 + 2χT up to first order their angular velocity. We calculate the mass, radius, and moment of inertia of neutron stars in this modified gravity. The results show that the impact of the matter-geometric coupling parameter is greater on lighter neutron stars in both of these modified gravity models.

Analysis of the Forces and Moments in Canine Bodily Movement with Different Clear Aligners’ Extraction Space Designs

This study aimed to optimize space closure efficiency by comparing the forces and moments exerted by different designs of clear aligners (CAs) during the movement of maxillary canines into the premolar extraction space. The forces and moments were measured using a multi-axis force/moment transducer on the maxillary right canine. The CAs were fabricated from thermoformed polyethylene terephthalate glycol. The following four edentulous space designs were tested: the edentulous space was left intact (Group 1); the edentulous space was replaced with a premolar pontic (Group 2); the edentulous space was replaced with a half-sized premolar pontic (Group 3); and the edentulous space was replaced with a rectangular column beam (Group 4). The maxillary right canine was moved 0.25 mm distally. All groups experienced buccodistal and intrusive forces; compared with the other groups, Group 1 showed significantly greater intrusive and smaller distal forces, and Group 4 showed significantly greater distal forces. All groups experienced distal tilting, lingual inclination, and mesial rotational moments. These findings suggest that modifying the thickness and extent of the adjacent teeth in the edentulous area of the CA can improve local stiffness, thereby reducing the tipping of the teeth into the edentulous space. This study emphasizes the importance of the CA design in controlling forces and moments for effective orthodontic treatment.

Comparison of knee biomechanical characteristics during gait between patients with knee osteoarthritis and healthy individuals

ObjectiveThis study aim to quantify the differences in knee biomechanics during gait between knee osteoarthritis (KOA) patients and healthy individuals. MethodsTwenty KOA patients (4 males and 16 females, 66.2 ± 7.7 years) and twenty controls (16 males and 4 females, 64.8 ± 5.4 years) were recruited for gait test using the motion capture system and force-platform system. The spatiotemporal parameters, knee kinematics and kinetics, and tibiofemoral contact force (TFCF) were calculated using an improved musculoskeletal model. ResultsKOA patients walked with reduced speed (48.6 %), stride length (32.9 %), stride height (33.0 %), time proportions of single-support phases (19.2 %), increased gait cycle time (31.0 %), time proportions of stance (8.5 %) and double-support phases (57.7–75.9 %). KOA patients had significant smaller peak flexion angle (29.1 %), flexion ROM (50.6 %) and peak flexion moment (90.2 %), greater peak adduction moment (KAM) (40.7 %), peak rotation moments (KRM) (50.0 %), KAM impulse (106.2 %) and KRM impulse (126.0 %). In proximodistal direction, greater medial TFCF impulse (238 %), total and medial first-peak TFCF (9.6 % and 15.2 %), and smaller lateral peak TFCF (33.3 %) and TFCF impulse (38.4 %) were found in KOA patients. Besides, significant differences were found in the total, medial and lateral peak TFCFs and TFCF impulses in mediolateral direction, and the medial and lateral TFCFs and TFCF impulses in anteroposterior direction. ConclusionsSignificant differences were found in the spatiotemporal parameters, knee kinematics and kinetics, and TFCF between the two groups. The results of this study have important implication for clinicians and rehabilitation physicians. These quantified biomechanical differences can provide data support for the personalized and quantified rehabilitation strategies, give suggestions for the exercises of KOA patients, help monitor disease, evaluate surgical treatment, and develop more effective preoperative planning and postoperative rehabilitation strategies.

Changes in rotator movement during early gait acquisition in after total hip arthroplasty

BackgroundIn walking in healthy adults, rotation of the hip joint affects stride length and shifts the center of gravity, but these are not seen in hip osteoarthritis which affects gait. In gait of total hip arthroplasty, there are few reports on changes in the horizontal plane. This study clarified the preoperative and early postoperative gait characteristics of patients undergoing total hip arthroplasty. MethodsThe analysis included 12 females who underwent initial total hip arthroplasty using a posterolateral approach. Gait was measured pre and postoperatively using a three-dimensional motion analysis device. Statistics were compared pre and postoperative range of motion, muscle strength, walking speed, stride length, gravity movement distance, trunk angle, hip joint angle, and joint moment. FindingsThe maximum hip abduction moment and trunk flexion angle to the surgical side were lower than in healthy subjects. The angle of internal rotation during the stance phase was significantly higher in the postoperative period. The distance of the center of gravity shift in the left and right directions was significantly decreased postoperatively. InterpretationGait disturbance was seen preoperatively and remained after surgery. Walking after total hip arthroplasty provides the hip joint rotates inward which is closer to normal walking. However, no change was observed in the external rotation moment of the hip joint during walking. We suspect that the invasiveness of the posterolateral approach of total hip arthroplasty affects the muscles for external rotation of the hip joint. This can also cause in gait disturbances.

A proposal for a simple characterization of stainless steel connections through an equivalent yield strength

Notwithstanding some recent contributions, there still appears to be a gap in the literature regarding the express evaluation of the moment–rotation performance of some connections fabricated from austenitic, duplex, or ferritic stainless steel, such as flush end-plate connections (FEP). In the present work, moving from a previous proposal, the authors investigate a simple approach for the practical characterization of these connections. The results from industry standard software, which is dedicated to the analysis of connections based on the component method and widely used in engineering practice, are compared with the results from a more refined numerical model. It is found that, by using conventional carbon steel procedures with an ad hoc ideal material model, the results can be made in line with some experimentally validated numerical simulations for stainless steel. The findings are discussed in detail and may turn useful from both a design and an assessment standpoint.