Torque Research Articles

BIFURCATION STATE AND RATIONAL DESIGN OF THREE-LAYER REINFORCED COMPOUND CONE-СYLINDER SHELL STRUCTURE UNDER COMBINED LOADING

An analytical-numerical approach to solving the problem of state bifurcation in terms of local and overall stability of a three-layer cone-cylinder shell structure discretely supported by intermediate rings, in particular of modern launch vehicles, under static combined loading by external pressure, axial forces, and torque is proposed in the paper taking into account the stiffness parameters of the intermediate rings in the plane of the initial curvature and for torsion. Corresponding solving equations for the problem are ordinary differential equations of the sixth order (for a cylindrical compart- ment with constant coefficients and for a conical one with variable coefficients along the axial coordinate). Differential relations that determine the conditions of conjugation through the intermediate ring are used. For the numerical solution, the finite difference method is used with central finite differences of the third and second order at the inner points of the shell determination segments and at its ends, respectively, and the second order differences with one step backward or forward at the conjugation points through the ring. The agreement of the calculation results with the known data for three-layer conical and cylindrical shells is shown, as well as in the limiting case, it is done when passing to a single-layer compound cone-cylinder structure. For the considered class of cone-cylinder shell structures, boundary surfaces are constructed that separate the stability region of the structure being under study, depending on the geometric and stiffness parameters of the compartments, reinforcing elements, and the external load condition. The external load effect on the parameter of the post-critical wave formation for the structure under investigation is studied, provid- ing the visualization of the deformation behavior. The analysis of the calculation results has shown that this approach to solving the problem of bifurcation and equistability of the compound structure compartments in relation to the local and overall forms of protrusion allows choosing rational geometric and stiff- ness parameters of the shell components and force elements in terms of improving the weight characteristics of the structure.

Lattice distortion of a (0001) twin constrained by grain boundaries in a p-type (bi,Sb)2Te3 alloy during three point bending deformation

Twinning, which is directly related to partial dislocation, has been extensively observed as a main plastic deformation mechanism in crystals. Generally, there are no other lattice defects inside the twins. By using transmission electron microscopy (TEM), we document, for the first time, the presence of lattice distortion of a (0001) twin within a deformed p-type (Bi,Sb)2Te3 alloy. Atomic scale analyses for the characteristics and mechanism of this lattice distortion of a (0001) twin have been systematically carried out with high resolution TEM (HRTEM) and geometric phase analysis (GPA) tool. Results reveal that the mechanism of lattice distortion of a (0001) twin can be attributed to the twisting deformation occurred near the twin boundaries under the effect of an external torque. Further, we constructed structure models of the lattice distortion of a (0001) twin based on HRTEM and GPA analysis.

Multi-objective parameter optimization strategy based on engine coordinated control for improving shifting quality

In order to address the poor shifting quality issue of a certain model of heavy-duty vehicles, a multi-objective parameter optimization strategy based on engine coordinated control is proposed. This strategy aims to improve shifting quality by reducing the sliding friction work and impact during the shifting process. The Non-Dominated Sorting Genetic Algorithm II (NSGA-II) is employed to perform multi-objective optimization on the coordinated control parameters, which include external control torque of the engine, start of fuel cut-off timing, and duration of fuel cut-off. By comparing the performance of different parameter combinations in terms of sliding friction work and impact, the optimal parameter combination is determined. Through bench testing verification, it has been demonstrated that utilizing the optimized parameters for engine coordinated control during the torque phase of the shifting process can significantly enhance shifting quality. This strategy provides an effective solution for addressing shifting quality issues.

Time characteristics of microsatellite attitude control at intervals between reac-tion wheels desaturations

The article is devoted to the processes study of changing the microsatellite reaction wheels angular velocities during its stabilization, turn and detumbling. Satellite control is considered under conditions of constant and harmonic external torques, as well as under gravitational, aerodynamic and magnetic disturbing torques. Expressions that describe the change in the reaction wheels angular velocities during satellite stabilization under the action of constant and harmonic torques at a frequency equal to the orbital angular velocity are given. The influence of the magnetic disturbing torque caused by the constant component of the satellite's dipole moment on the accumulation of the reaction wheels angular momentum has been studied. The formula for determining the magnitude of the reaction wheels angular velocities oscillations was obtained using a model of the Earth's magnetic field in the form of the straight dipole and taking into account a circular orbit. Moreover, its use for calculating the maximum values of angular velocities gives results that are very close to the results of modeling taking into account accurate models of the Earth’s magnetic field and the satellite’s center of mass trajectory. The maximum possible operating time intervals of the control system without forced desaturation of its controls are estimated.

Changing the horizontal position of a fixed backpack load: The effect on postural stability in young adults.

Modifying the horizontal position of the load in a backpack will change the size of the external torque it creates on the wearer but the effect on postural stability is unclear. To determine if changing the horizontal position of a fixed backpack load affects postural stability in young adults. A backpack was attached to a steel frame with a bar protruding posteriorly. A fixed load (5% body mass) was placed at three distances along the bar - 0 m, 0.20 m, and 0.40 m. Centre of pressure (CoP) derived measurements were recorded from a force platform sampling at 100 Hz. For each condition participants performed three 90s narrow stance trials with their eyes closed whilst standing on a firm surface. A comparison was made across unloaded (no backpack) and loaded conditions. There was an immediate decrease in postural stability when a loaded backpack was worn. Only two of the CoP derived measures (Total Excursion - TEx, and Mean Velocity Total Excursion - MVel TEx) differed between the loaded at 0.20 m and loaded at 0 m conditions. All CoP derived measures differed between the loaded at 0.40 m and loaded at 0 m conditions. Furthermore, three of the CoP derived measures (Anterior/Posterior Root Mean Square - A/P RMSq, TEx, and MVel TEx) differed between the loaded at 0.40 m and loaded at 0.20 m conditions. The distribution of a load within a backpack must be carefully considered. The findings for the 0.40 m condition are important for the use and design of large backpacks used by multi-day hikers, travellers, and the military.

Development of an Assistive Ankle-Foot Exoskeleton With Sensorized Silicone-Based Insole

Abstract Millions of people with disabilities, the elderly, and individuals suffering from physical deformities rely on assistive devices to perform basic actions and movements. With the increasing number of these individuals, the lack of available medical equipment/assistive personnel, and the size, bulkiness, and cost of assistive devices found in rehabilitation centers, there has been a growing interest in the research for lighter, portable, and cost-effective personal external assistive devices. In this paper, a new prototype of an ankle-foot exoskeleton was engineered with low-cost printed material that maintains structural integrity while providing appropriate comfort and support for the wearer. This ankle-foot exoskeleton was fabricated using thermoplastic polyurethane (TPU) and polylactic acid (PLA), common materials used for three-dimensional printing. The printed pieces were combined with zinc-nickel hinge joints to create a one-degree-of-freedom (DOF) support system. Finite element analysis on both fabricated parts indicates an average safety factor of 4 at applied loads of 700 N and 100 N to the foot and calf sections respectively. A pressure insole system consisting of a silicone-based pressure mold, force-sensitive resistors, and a microcontroller circuit was developed to measure foot pressure experienced during standing and stepping motion. This exoskeleton was also subjected to actuation tests via an external torque motor to obtain ankle trajectory profiles at various walking speeds.

Length-Tension Differences Between Concentric and Eccentric Shoulder Rotation Strength.

Giordano, KA, Cassidy, MM, and Oliver, GD. Length-tension differences between concentric and eccentric shoulder rotation strength. J Strength Cond Res 38(2): 253-258, 2024-Eccentric contractions generally produce more force than concentric contractions. However, if length-tension relationships affect both contractions equally remains unknown. Therefore, our purpose was to compare concentric versus eccentric shoulder external and internal rotation strength across a continuous 90° arc. Fifty-two physically active individuals performed isokinetic concentric and eccentric shoulder external rotation and internal rotation through a 90° arc (forearm horizontal to forearm vertical) with the shoulder elevated in both the frontal and scapular planes. Statistical parametric mapping analysis compared concentric and eccentric trials within subjects. Frontal plane eccentric external rotation torque was greater than concentric 30°-90° (p < 0.01) external rotation, and concentric external rotation torque was greater 5°-15° external rotation (p = 0.01). Frontal plane, eccentric internal rotation torque was greater than concentric 15°-55° external rotation (p < 0.01), and concentric torque was greater at forearm horizontal (p = 0.05) and 70°-90° external rotation (p < 0.01). Scapular plane eccentric external rotation torque was greater than concentric 30°-90° external rotation (p < 0.01) and concentric external rotation torque was greater 5°-20° external rotation (p < 0.01). Scapular plane eccentric internal rotation torque was greater than concentric 15°-60° external rotation (p < 0.01), and concentric torque was greater at forearm horizontal (p = 0.05) and 78°-90° external rotation (p = 0.02). Coaches, clinicians, and researchers should interpret data from studies reporting isokinetic data with the understanding that isokinetic peak strength values are not comparing the same muscle length and are not an appropriate measure for all muscle lengths. Furthermore, shoulder stability is affected through decreased eccentric force production at end ranges of shoulder rotation.

Magnitude and variability of individual elbow load in repetitive baseball pitching

In baseball pitchers the elbow is exposed to high and repetitive loads (i.e. external valgus torque), caused by pitching a high number of balls in a practice session or game. This can result in overuse injuries like the ulnar collateral ligament (UCL) injury. To understand injury mechanisms, the effect of repetitive pitching on the elbow load magnitude and variability was investigated. In addition, we explored whether repetitive pitching affects elbow muscle activation during pitching. Fifteen pitchers threw each 60 to 110 balls. The external valgus torque and electromyography of three elbow muscles were quantified during each pitch. Linear mixed model analyses were performed to investigate the effect of repetitive pitching. On a group level, the linear mixed models showed no significant associations of repetitive pitching with valgus torque magnitude and variability and elbow muscle activity. Significant differences exist between pitchers in their individual trajectories in elbow valgus torque and muscle activity with repetitive pitching. This shows the importance of individuality in relation to repetitive pitching. In order to achieve effective elbow injury prevention in baseball pitching, individual characteristics of changes in elbow load and muscle activity in relation to the development of UCL injuries should be investigated.

Application of External Torque Observer and Virtual Force Sensor for a 6-DOF Robot

Application of External Torque Observer and Virtual Force Sensor for a 6-DOF Robot

Neuromechanical Model-Based Corrective Torque Estimation During Weight Shifting in Lower Limb Amputees

As a consequence of limb loss, unilateral lower limb amputees (LLAs) exert additional flexion torque in the intact limb during postural balance, leading to other secondary complications. A prosthetic device with torque delivery is required to avoid such complications. However, estimating desired torque is an acknowledged challenge in this domain. Motivated by the above, this paper focuses on estimating the corrective torque required from an assistive device to balance the individual while performing weight-shifting exercises. Further, a healthy individual’s inverted pendulum (IP) model is explored to model LLA’s dynamics during weight-shifting. The model and the control strategy are validated using forward and backward body lean angles recorded from healthy and LLA individuals. Finally, a robust Proportional Integral Derivative controller is designed to estimate the corrective torque for maintaining the postural balance during weight-shifting. Along with the IP dynamics, a suitable control law based on Coefficient Diagram Method achieves the experimentally recorded body lean angle. The proposed control scheme is validated through simulation studies to evaluate the tracking performance in two different biomechanically relevant IP postural models. The findings assist in determining the external torque required to maintain the postural balance during gait initiation and compensatory measures for pathologically reduced torque. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —Gait initiation is a transition between vertical posture and gait. Since vertical stance is inherently unstable, a postural adjustment occurs before gait initiates, propelling the center of mass forward and towards the first stance leg. The absence of flexor torque in the amputated limb causes a loss of postural stability during weight shifting activities. In the case of powered exoskeletons and prosthetic devices, a prior estimation of corrective torque through a computational approach helps to select a suitable actuator that provides an appropriate joint torque while maintaining the postural balance. As a result, an efficient computational model of gait initiation that accounts for neuromuscular system components before designing assistive devices is necessary. The controllers further provide corrective action to the assistive device to obtain robust and optimal coordination between the prosthetic element and gait. Therefore, this study demonstrates the significance of neuromuscular controller and assists in determining how much corrective torque from an external device is required to maintain postural stability and adaptability during weight shifting exercises. The effectiveness of the neural controller is also tested for real-time data to compensate for the effect of external disturbance and noise, thereby achieving a proper and controlled degree of movement in amputee users. These findings could provide one of the fundamental aspects of gait initiation model paradigms of compensatory measures for pathologically diminished torque and contribute to developing low-cost prosthetic solutions for the benefit of the rehabilitation society in developing countries.

Application of External Torque Enhances the Detection of Subtle Syndesmotic Ankle Instability in a Weightbearing CT

Category: Sports; Trauma Introduction/Purpose: Syndesmotic ankle injuries are present in one-fourth of all ankle trauma and may lead to syndesmotic instability or posttraumatic ankle osteoarthirtis on the long term. At present, they continue to impose a diagnostic dilemma our clinical practice. While magnetic resonance imaging lacks application of load to the ankle joint, plain weightbearing radiographs are skewed by superposition of the osseous structures. The recent advent of weightbearing cone-beam CT (WBCT) overcomes these drawbacks by imaging both ankles during bipedal stance. However, it remains debated whether syndesmotic ankle injuries should be imaged under weightbearing conditions and/or during application of external rotation. Therefore, we aimed to implement both weightbearing and external rotation in the assessment of syndesmotic ankle injuries using WBCT imaging combined with 3D measurement techniques. Methods: In this retrospective study, patients with an acute syndesmotic ankle injury were analyzed using a WBCT (N= 21; Age= 31.64±14.07 years old). Inclusion criteria were an MRI confirmed syndesmotic ligament injury imaged by a WBCT of the ankle during weightbearing and combined weightbearing-external rotation. Exclusion criteria consisted of fracture associated syndesmotic injuries. For the external rotation protocol, the patient was asked to internally rotate the shin while ensuring that the foot remained firmly plantigrade until pain (Visual Analogue Scale &gt; 8/10) or a maximal range of motion was reached. 3D models were generated from the CT slices. Tibiofibular displacement and Talar Rotation were quantified by automated 3D measurements using a custom-made Matlab® script; Anterior Tibiofibular distance (ATFD), Alpha angle, posterior Tibiofibular distance (PTFD) and Talar rotation (TR) angle in comparison to the contralateral non-injured ankle. Results: The difference in neutral-stressed Alpha angle and ATFD showed a significant difference between patients with a syndesmotic ankle lesion and contralateral control (P = 0.046 and P = 0.039, respectively). The difference in neutral-stressed PTFD and TR angle did not show a significant difference between patients with a syndesmotic ankle lesion and healthy ankles (P = 0.492; P = 0.152, respectively). Conclusion: Application of combined weightbearing-external rotation reveals an increased ATFD in patients with syndesmotic ligament injuries (Figure 1). This study provides the first insights based on 3D measurements to support the potential relevance of applying external rotation during WBCT imaging. In clinical practice, this could enhance the current diagnostic accuracy of subtle syndesmotic instability in a non-invasive manner. However, future studies are required to determine cut-off values that may indicate the amount of displacement that might lead to chronic instability and require a certain type of treatment strategy.

Increased Posterior Tibial Slope Increases Force on the Posterior Medial Meniscus Root

Background: Posterior medial meniscus root (PMMR) tears have been associated with increased posterior tibial slope, but this has not been fully evaluated biomechanically. In addition, the effects of knee flexion and rotation on the PMMR are not well understood biomechanically because of technological testing limitations. A novel multiaxial force sensor has made it possible to elucidate answers to these questions. Purpose: (1) To determine if increased posterior tibial slope results in increased posterior shear force and compression on the PMMR, (2) to evaluate how knee flexion angle affects PMMR forces, and (3) to assess how internal and external rotation affects force at the PMMR. Study Design: Controlled laboratory study. Methods: Ten fresh-frozen cadaveric knees were tested in all combinations of 3 posterior tibial slopes and 4 flexion angles. A multiaxial force sensor was connected to the PMMR and installed below the posterior tibial plateau maintaining anatomic position. The specimen underwent a 500-N compression load followed by a 5-N·m internal torque and a 5-N·m external torque. The magnitude and direction of the forces acting on the PMMR were measured. Results: Under joint compression, an increased tibial slope significantly reduced the tension on the PMMR between 5° and 10° (from 13.5 N to 6.4 N), after which it transitioned to a significant increase in PMMR compression, reaching 7.6 N at 15°. Under internal torque, increased tibial slope resulted in 4.7 N of posterior shear at 5° significantly changed to 2.0 N of anterior shear at 10° and then 8.2 N of anterior shear at 15°. Under external torque, increased tibial slope significantly decreased PMMR compression (5°: 8.9 N; 10°: 4.3 N; 15°: 1.1 N). Under joint compression, increased flexion angle significantly increased medial shear forces of the PMMR (0°, 3.8 N; 30°, 6.2 N; 60°, 7.3 N; 90°, 8.4 N). Under internal torque, 90° of flexion significantly increased PMMR tension from 2.3 N to 7.5 N. Under external torque, 30° of flexion significantly increased PMMR compression from 4.7 N to 12.2 N. Conclusion: An increased posterior tibial slope affects compression and anterior shear forces at the PMMR. An increased flexion angle affects compression, tension, and medial shear forces at the PMMR. Clinical Relevance: The increase in compression and posterior shear force when the knee is loaded in compression may place the PMMR under increased stress and risk potential failure after repair. This study provides clinicians with information to create safer protocols and improve repair techniques to minimize the forces experienced at the PMMR.

Research on dynamic parameter identification and collision detection method for cooperative robots

PurposeThe safety performance of cooperative robots is particularly important. This paper aims to study collision detection and response of cooperative robots, which meet the lightweight requirements of cooperative robots and help to ensure the safety of humans and robots.Design/methodology/approachThis paper proposes a collision detection, recognition and response method based on dynamic models. First, this paper identifies the dynamic model of the robot. Second, an external torque observer is established based on the model, and a dynamic threshold collision detection method is designed to reduce the interference of model uncertainty on collision detection. Finally, a collision position and direction estimation method is designed, and a robot collision response strategy is proposed to reduce the harm caused by collisions to humans.FindingsComparative experiments are conducted on static threshold and dynamic threshold collision detection, and the results showed that the static threshold only detected one collision while the dynamic threshold could detect all collisions. Conducting collision position and direction estimation and collision response experiments, and the results show that this method can determine the location and direction of collision occurrence, and enable the robot to achieve collision separation.Originality/valueThis paper designs a dynamic threshold collision detection method that does not require external sensors. Compared with static threshold collision detection methods, this method can significantly improve the sensitivity of collision detection. This paper also proposes a collision position direction estimation method and collision separation response strategy, which can enable robots to achieve post collision separation and improve the safety of cooperative robots.

Meniscotibial Ligament Insufficiency Increases Force on the Posterior Medial Meniscus Root

Background: Posterior medial meniscus root (PMMR) tears are a challenge to assess and treat. However, the forces sustained at the PMMR are yet to be fully characterized. In addition, it has been shown that meniscotibial ligament (MTL) injuries happen before PMMR tears, suggesting that insufficiency of the MTL results in a change of forces acting on the PMMR. Purpose/Hypothesis: The purpose of this study was to evaluate the 3-dimensional forces acting on the PMMR in the intact, MTL cut, and MTL tenodesis states. It was hypothesized that the MTL cut state would increase medial shear forces seen at the PMMR, whereas the medial shear force in the MTL tenodesis state would return PMMR forces to that of the intact state. Study Design: Controlled laboratory study. Methods: Ten fresh-frozen cadaveric knees were tested in 3 states (intact, MTL cut, and tenodesis). A 3-axis load cell was installed below the posterior tibial plateau and attached to the enthesis of the PMMR. The specimen was mounted to a load frame that applied an axial load, an internal torque, and an external torque. The amount of compression-tension, mediolateral shear force, and anteroposterior shear force acting on the PMMR was measured. Results: When the joint was loaded in compression, the MTL cut state significantly increased compression of the PMMR (P = .0368). The tenodesis state did not significantly restore forces of the PMMR (P = .008). When the joint was loaded in external torque, the MTL cut state significantly increased compression (P < .0001) and significantly decreased anterior shear on the PMMR (P = .0003). The tenodesis state did not significantly restore forces on the PMMR to the intact state (P < .0001). Increased flexion angle significantly increased medial shear forces of the PMMR when the joint was loaded in compression (P < .007 at every angle). Conclusion: When evaluated biomechanically, MTL insufficiency resulted in increased compressive force at the PMMR. A single-anchor centralization procedure did not restore PMMR forces to that of the intact state. Increased knee flexion angle resulted in increased medial shear force on the PMMR. Clinical Relevance: The findings in this study provide clinicians information on PMMR forces when the MTL is disrupted. These data can aid in the decision-making for adding an MTL repair to augment PMMR repairs.

LSTM-based external torque prediction for 6-DOF robot collision detection

LSTM-based external torque prediction for 6-DOF robot collision detection

A Comprehensive Pattern Recognition Neural Network for Collision Classification Using Force Sensor Signals

In this paper, force sensor signals are classified using a pattern recognition neural network (PRNN). The signals are classified to show if there is a collision or not. In our previous work, the joints positions of a 2-DOF robot were used to estimate the external force sensor signal, which was attached at the robot end-effector, and the external joint torques of this robot based on a multilayer feedforward NN (MLFFNN). In the current work, the estimated force sensor signal and the external joints’ torques from the previous work are used as the inputs to the proposed designed PRNN, and its output is whether a collision is found or not. The designed PRNN is trained using a scaled conjugate gradient backpropagation algorithm and tested and validated using different data from the training one. The results prove that the PRNN is effective in classifying the force signals. Its effectiveness for classifying the collision cases is 92.8%, and for the non-collisions cases is 99.4%. Therefore, the overall efficiency is 99.2%. The same methodology and work are repeated using a PRNN trained using another algorithm, which is the Levenberg–Marquardt (PRNN-LM). The results using this structure prove that the PRNN-LM is also effective in classifying the force signals, and its overall effectiveness is 99.3%, which is slightly higher than the first PRNN. Finally, a comparison of the effectiveness of the proposed PRNN and PRNN-LM with other previous different classifiers is included. This comparison shows the effectiveness of the proposed PRNN and PRNN-LM.

Model-based and model-free collision detection and identification for a parallel Delta robot with uncertainties

This paper presents two methods for human collision detection and identification for a parallel Delta robot considering uncertainties. In the model-based, a generalized momentum observer based on the explicit model of the Delta robot is used to estimate a proposed uncertainty model without collision. A linear regression algorithm is approached to recognize actuator hysteresis friction models and modeling error parameters, constructing the uncertainty model. The boundary and convergence of the identification parameters are guaranteed based on a least square method. Then, the estimated uncertainty is compared with the generalized momentum observer to detect and identify collision impacts as external torques. In the model-free, the neural network model for actuated torque prediction controlling the Delta robot is developed based on a model-driven and data-driven approach. The training procedure of the proposed network only uses no collision datasets. The model-free method uses a neural network to provide detection signals and external torques identified by comparing its conservative predictions to the measured torques when a collision occurs. In this work, only low-cost current sensors and low-resolution encoders are attached to the Delta robot system for generating the datasets. Finally, the identification capacity of the proposed methods is also compared with a force sensor to verify the effectiveness in real-time implementation.

Analysis of Sharp Eagle Oscillating Surge Wave Energy Converter Based on a Two-Dimensional Numerical Wave Flume Model

To investigate the overtopping and slamming phenomena that occur in the interactions between waves and oscillating surge wave energy converters (OSWECs), a two-dimensional numerical wave flume was established using computational fluid dynamics (CFD) software Fluent by adding the momentum source terms into the original Navier–Stokes equation. Numerical convergence studies of the mesh sizes and time steps were firstly performed to ensure the sufficient accuracy of the numerical model. The variations in the wave heights along the wave propagation direction in the wave-generating area, working area, and wave-absorbing area were analyzed. The dynamics of the flap-type OSWEC were simulated using the overset mesh function embedded in Fluent. In addition, the numerical results were compared with the experimental data, and good agreements were achieved. External torque was applied to the hinge joint of the OSWEC to simulate the forces due to the power take-off (PTO) system, and the identified optimal PTO damping was compared with the numerical results based on the potential flow theory, which verified the correctness of the numerical PTO system. On this basis, nonlinear wave slamming by the sharp-eagle OSWEC was analyzed. The results show that under certain incident wave conditions, the sharp-eagle OSWEC can effectively reduce the maximum rotation angle and angular velocity compared with those of the flap-type OSWEC, and there is no overtopping that occurring for the sharp-eagle OSWEC. Furthermore, the sharp-eagle OSWEC performs better than the flap-type OSWEC.

Application of external torque enhances the detection of subtle syndesmotic ankle instability in a weight-bearing CT.

Acute syndesmotic ankle injuries continue to impose a diagnostic dilemma and it remains unclear whether weightbearing and/or external rotation should be added during the imaging process. Therefore, the aim of this study was to assess if combined weightbearing and external rotation increases the diagnostic sensitivity of syndesmotic ankle instability using weightbearing CT (WBCT) imaging, compared to isolated weightbearing. In this retrospective study, patients with an acute syndesmotic ankle injury were analysed using a WBCT (N = 21; Age = 31.6 ± 14.1years old). Inclusion criteria were an MRI confirmed syndesmotic ligament injury imaged by a WBCT of the ankle during weightbearing and combined weightbearing-external rotation. Exclusion criteria consisted of fracture associated syndesmotic injuries. Three-dimensional (3D) models were generated from the CT slices. Tibiofibular displacement and talar rotation were quantified using automated 3D measurements (anterior tibiofibular distance (ATFD), Alpha angle, posterior Tibiofibular distance (PTFD) and Talar rotation (TR) angle in comparison to the contralateral non-injured ankle. The difference in neutral-stressed Alpha angle and ATFD showed a significant difference between patients with a syndesmotic ankle lesion and contralateral control (P = 0.046 and P = 0.039, respectively). The difference in neutral-stressed PTFD and TR angle did not show a significant difference between patients with a syndesmotic ankle lesion and healthy ankles (n.s.). Application of combined weightbearing-external rotation reveals an increased ATFD in patients with syndesmotic ligament injuries. This study provides the first insights based on 3D measurements to support the potential relevance of applying external rotation during WBCT imaging. In clinical practice, this could enhance the current diagnostic accuracy of subtle syndesmotic instability in a non-invasive manner. However, to what extent certain displacement patterns require operative treatment strategies has yet to be determined in future studies. Level III.

NOVEL SINGLE-STRAND ‘SHORT ISOMETRIC CONSTRUCT’ (SIC) MEDIAL COLLATERAL LIGAMENT RECONSTRUCTION RESTORES VALGUS AND ROTATIONAL STABILITY THROUGHOUT KNEE RANGE OF MOTION

AbstractIntroductionPersistent medial laxity increases the risk of failure for ACL reconstruction. To address this, multiple reconstruction techniques have been created. To date, no single strand reconstruction constructs have been able to restore both valgus and rotational stability. In response to this, a novel single strand Short Isometric Construct (SIC) MCL reconstruction was developed.MethodsEight fresh-frozen cadaveric specimens were tested in three states: 1) intact 2) after sMCL and dMCL transection, and 3) after SIC MCL reconstruction. In each state, four loading conditions were applied at varying flexion angles: 90N anterior drawer, 5Nm tibial external rotation torque, 8Nm valgus torque, and combined 90N anterior drawer plus 5Nm tibial external rotation torque.ResultsTransection of the sMCL and dMCL resulted in increased laxity with external rotation torque, valgus torque, and combined anterior drawer plus external rotation. SIC MCL reconstruction restored external rotation and valgus stability to intact levels throughout all degrees of flexion. In the combined test SIC MCL reconstruction also restored stability to intact levels for both anterior distraction and external rotation throughout the range of motion. No significant differences were noted between intact and SIC reconstruction.ConclusionThe single-limb short isometric construct (SIC) MCL reconstruction restored native valgus and rotatory stability to a sMCL- and dMCL-deficient knee in biomechanical testing.