External Moment Research Articles

Effect of Hind- and Fore-Foot Eversion on Positional and Rotational Displacement of the Knee in Standing Posture.

We investigated the effects of hindfoot and forefoot eversion on the knee's positional and rotational displacement, plantar pressure, and foot discomfort in a standing posture, beyond the traditional focus on external knee adduction moments (EKAM) in lateral wedge insoles. Twenty-six healthy participants underwent hindfoot eversion from 0 to 10 degrees in 2-degree increments, and forefoot eversion from 0 degrees to the hindfoot eversion angle in 2-degree increments in a standing posture. At each eversion angle, the knee's medial displacement, EKAM's moment arm decrease, plantar pressure changes, and foot discomfort were obtained and compared across varying angles. Both hindfoot-only and entire-foot eversion led to significant medial knee displacement and the EKAM's moment arm decrease, with more pronounced effects in entire-foot eversion. At each hindfoot eversion angle, increasing forefoot eversion resulted in significant medial knee displacement and EKAM's moment arm decrease. Lower leg rotations were not significantly affected in hindfoot-only eversion but displayed significant medial tilting and internal rotation in entire-foot eversion at specific combinations. Varying eversion angles significantly influenced the forefoot pressure, with heel pressure remaining unaffected. Notably, the lateral forefoot pressure increased significantly as the forefoot eversion angle increased, particularly at higher hindfoot eversion angles. Foot discomfort increased significantly with higher eversion angles, particularly in entire-foot eversion, and also increased significantly as the forefoot eversion angle increased at higher hindfoot eversion angles. Insole configurations incorporating 6-10 degrees of hindfoot eversion and 40-60% forefoot eversion of the hindfoot angle may offer optimized biomechanical support for knee osteoarthritis patients.

Effects of smartphone use while walking on external knee abduction moment peak: A crossover randomized trial on an instrumented treadmill

IntroductionIn addition to its effects on cognitive awareness, smartphone use while walking may reduce the speed, regularity, and symmetry of walking. Although its effects on spatiotemporal gait parameters, such as walking speed and step width, have already been studied, little is currently known about the impact of smartphone dual tasking on lower limb kinetics. Research questionDoes smartphone use during walking alter gait patterns (i.e., walking speed and step width) and consequently external knee moments? MethodsIn a four-period crossover trial, external knee moment peaks, walking speed, and step width were assessed in 27 healthy adults during matched-speed walking, self-paced walking, self-paced walking with spoken calculation tasks, and self-paced walking with smartphone-entered calculation tasks. Differences between the smartphone use condition and all other conditions were determined using repeated measures ANOVA with predefined contrasts. ResultsDecreased walking speed and increased step width were observed during smartphone use. The mean external knee abduction moment peak (Nm/kg) differed significantly (p < 0.01) across the intervention condition, namely walking with smartphone-entered calculations (0.15; 95 % CI: 0.12, 0.18), and the control conditions, namely matched-speed walking (0.11; 95 % CI: 0.08, 0.13), self-paced walking (0.11; 95 % CI: 0.09, 0.14), and walking with spoken calculations (0.14; 95 % CI: 0.12, 0.16). After confounder adjustment for walking speed, step width, gender, and age, this primary outcome was significantly different between using the smartphone and self-paced walking (p < 0.01, r = 0.51). This effect size was reduced when comparing smartphone use with spoken calculations (p = 0.04, r = 0.32). ConclusionWhen using a smartphone while walking, walking speed is slowed down, step width is increased, and knee moments are adversely altered compared to walking without dual tasking. These altered knee moments are partially, but not entirely, attributable to the cognitive calculation task. These effects are age-independent, but women are more affected than men. Nevertheless, it remains unclear whether sustained walking while using a smartphone adversely affects the development of knee joint pathologies.

The Influence of Knee Position on Ultrasound Imaging of Femoral Cartilage in Individuals with Anterior Cruciate Ligament Reconstruction.

Articular cartilage is important for knee function and can be imaged using ultrasound. The purpose was to compare femoral cartilage thickness and echo intensity (EI) measured at 90° and 140° of knee flexion and between limbs in a cohort with unilateral anterior cruciate ligament reconstruction (ACLR). We also examined associations between gait biomechanics and cartilage outcomes. Twenty-seven individuals with primary unilateral ACLR participated (12 men, 15 women; age = 22.3 ± 3.8 years; time since ACLR = 71.2 ± 47.2 months). Ultrasound was used to obtain femoral cartilage measurements. Gait outcomes included peak KFA (knee flexion angle) and peak external knee flexion moment (KFM). Cartilage outcomes were compared using a 2 (position) × 2 (limb) repeated measures ANOVA (analysis of variance). Gait and cartilage associations were assessed using linear regression. There were no position × limb interactions for any cartilage outcome (all P > 0.05). Medial (P = 0.038) and central cartilage (P < 0.001) were thicker, whereas central (P = 0.029) and lateral cartilage EI (P = 0.003) were lower when measured at 90° than those at 140° of knee flexion. Medial cartilage was thicker in the ACLR than that in the contralateral limb (P = 0.016). A larger KFM was associated with thicker medial cartilage (ΔR2 = 0.146, P = 0.021) and central cartilage (ΔR2 = 0.159, P = 0.039) measured at 140° of knee flexion in the ACLR limb but not at 90°. Findings suggest that imaging position influences cartilage thickness and EI measurements in individuals with ACLR and should be considered in study designs and clinical evaluation. A greater KFM was associated with thicker cartilage within specific portions of the distal femur.

Stiffness analysis and parameter optimization of six-dimensional force sensor with the novel circular flexible spherical joint

As robot haptic provider, six-dimensional force sensors are an indispensable component of industrial intelligence. To address the disadvantages of the existing six-dimensional force sensor, a novel circular flexible spherical joint is proposed, its stiffness model is derived by numerical analysis method and microelement, and the stiffness model of the circular flexible spherical joint is verified by finite element simulation. A parallel six-dimensional force sensor is designed based on a circular flexible spherical joint, and a mathematical model of the sensor was established. Based on the genetic algorithm, the structural optimization design of the circular flexible spherical joint was performed, and the structural parameters of the circular flexible spherical joints are obtained by analyzing isotropy. Finally, according to the optimization results, a sensor was developed and calibration experiments were carried out. The experimental results show that the maximum error of the sensor is 1.85%, which verifies the effectiveness of the mathematical model of the sensor, which has high measurement accuracy and can accurately measure the six-dimensional external force and moment applied to the sensor.

Shear stress migration in a tapered girder with trapezoidal corrugated steel webs

This study conducted a comprehensive investigation into the shear stress migration of a tapered prestressed concrete (PC) continuous box girder bridge with trapezoidal corrugated steel webs (TCSWs) throughout the entire construction process, including cantilever construction, structural system transformation and external prestressing tendon tensioning. The results revealed that the basic assumptions, which state that TCSWs bear all the shear force and that only the vertical component of the external prestressing contributes to shear stress when considering its contribution, are not valid for the shear design of tapered PC girder bridges with TCSWs. The horizontal component of the external prestressing and bending moments can cause additional shear forces via the Resal effect, which results in the migration of the shear stresses between the curved bottom concrete slabs and TCSWs. This study investigated the mechanism through which the Resal effect and external prestressing influence the migration of shear stress in the entire construction process. The results revealed that within continuous girders, the Resal effect exhibits both positive and negative implications. Specifically, the negative Resal effect exerts an unfavorable influence, resulting in an increase in the shear stress experienced by the TCSWs. Moreover, this study introduced a modified shear method that that takes into account the influence of bending moments and the horizontal component of external prestressing. In contrast to basic shear methods, this approach provides notably heightened accuracy.

DYC Design for Autonomous Distributed Drive Electric Vehicle Considering Tire Nonlinear Mechanical Characteristics in the PWA Form

This paper presents a novel direct yaw moment control (DYC) strategy for autonomous distributed drive electric vehicle (DDEV) to improve path-following driving stability under critical maneuvers. Due to the fact that the tire mechanical characteristics show highly nonlinear under those critical conditions, the piecewise affine (PWA) identification method is chosen in this work to model the tire nonlinear mechanical characteristics since it shows best model accuracy/simplicity compromise for system control design. On this basis, to properly reflect the coupling behaviors between longitudinal motion and lateral motion, the vehicle dynamics model which considers the tire nonlinear mechanical characteristics in the PWA form is established. By analyzing the phase plane of vehicle nonlinear model, a novel external yaw moment calculation method based on global fast terminal sliding mode (GFTSM) control method is applied to the upper layer of DYC architecture for eliminating the errors of yaw rate and sideslip angle. Then, different weight coefficients are allocated to obtain the final external yaw moment. In the lower controller, the optimal four-wheel torque is distributed according to a concise and accurate algorithm in which adaptive weight coefficients are considered. The simulation results verify the effectiveness of the proposed control strategy in improving the driving stability performance of autonomous DDEV against two other control strategies under three extreme conditions.

Effects of shoe collar types on ankle and knee biomechanics characteristics when performing the side-step cutting task

ABSTRACT This study aimed to examine the effect of football shoes with different collar types on ankle and knee kinematic and kinetics features during 45° and 135° side-step cutting tasks. Fifteen healthy college football players volunteered for the study. Each participant was instructed to perform side-step cutting tasks with high, low, and no collar football shoes. The kinematic and ground reaction force data were measured using a Vicon motion capture system and a Kistler force plate, respectively. Two-way MANOVAs with repeated measures were used to examine the effect of shoe collar type and task conditions. There were no interaction effects. The high collar football shoe showed decreased ankle range of motion in the sagittal plane (p = 0.010) and peak ankle external rotation moment (p = 0.009) compared to the no collar football shoe. The high (p = 0.025) and low (p = 0.029) collar football shoes presented greater peak ankle external rotation angles than the no collar football shoe. These results imply that football shoes with high collars made of high intensity knitted fabric could be used to restrict ankle joint movement, with potential implications for decreasing the risk of ankle sprain injuries in football players.

Stage separation of recoverable liquid launch vehicle by using moving pulsating ball analogue for propellant sloshing

In the process of stage separation of recoverable liquid launch vehicles, because of the large amount of residual fuel in the storage tanks, the influence of liquid sloshing on separation safety must be considered. Considering calculation simplicity and operation practicability, the Moving Pulsating Ball Model (MPBM) of large amplitude liquid sloshing is introduced into the calculation of launch vehicle stage separation. Combining the dynamic equation of the model with the energy relationship during “breathing movement”, the formula calculating the force of liquid on the rigid body is derived. Compared with the calculations of commercial CFD calculation software, the accuracy of MPBM model is verified. Then, all the external forces and moments are applied to the rigid body of the stages, so that the translational and rotational dynamic equations of the stages are obtained respectively. According to the relative position of the two stages, the geometric shape of the interstage section and the engine of the second stage, the minimum clearance in the separation process can be decided to guarantee that the separation process is safe.

Evaluation of a Method to Estimate Foot Eversion Moments During the Support Phase of Running.

Excessive external eversion moments acting on the ankle derived from the ground reaction force (GRF) during the support phase of running are considered a risk factor for overuse lower-limb injuries. The external eversion moment is considered to be dominated by the moment derived from the vertical GRF. However, no studies have directly evaluated the accuracy with which external eversion moment can be estimated with this information. Thus, the objective of this study was to evaluate the extent to which external eversion moment can be estimated from external eversion moment derived from vertical GRF. From three-dimensional foot coordinates and GRF data of 28 healthy participants, we computed external eversion moment (EMrun), center of the ankle coordinates (ANKrun), center of pressure coordinates (COPrun), and vertical GRF (VGRFrun) during the support phase of running. Moreover, we computed center of the ankle joint coordinates (ANKstand) and vertical GRF (VGRFstand) in the resting standing position. A highly significant correlation was observed between EMrun and external eversion moment derived from vertical GRF ([COPrun - ANKrun] × VGRFrun), with a contribution of 84.7%. Moreover, a highly significant correlation was observed between EMrun and (COPrun - ANKstand) × VGRFstand, with a contribution of 81.5%. These results indicate that external eversion moment can be estimated from the external eversion moment derived from vertical GRF with high accuracy. Moreover, it was found that the accuracy did not decrease even if the data of center of ankle and vertical GRF were replaced with the data during standing.

Lower Body Joint Moments during the Golf Swing in Older Adults: Comparison to Other Activities of Daily Living.

Golf participation has increased dramatically in the last several years. With this increase in participation, clinicians need better evidenced based strategies to advise those golfers with different pathologies when it is safe to return to the game. Golf teaching professionals also need to understand how to alter golf mechanics to protect injured and/or diseased joints in golfers to allow them to play pain free and avoid further injury. This study used a 3-dimensional link segment model to calculate the net joint moments on the large lower limb joints (knee and hip) during golf (lead and trail leg) and two commonly studied activities of daily living (gait and sit-to-stand) in 22 males, healthy, adult golfers. It also examined the correlations between these knee and hip joint loads and club head speed. The external valgus knee moment and the internal hip adduction moment were greater in the lead leg in golf than in the other activities and were also correlated with club head speed. This indicates a strategy of using the frontal plane GRF moment during the swing. The internal hip extension and knee flexion moment were also greater in the golf swing as compared with the other activities and the hip extension moment was also correlated with club head speed. This emphasizes the importance of hip extensor (i.e., gluteus maximus and hamstring) muscle function in golfers, especially in those emphasizing the use of anterior-posterior ground reaction forces (i.e., the pivoting moment). The golf swing places some loads on the knee and the hip that are much different than the loads during gait and sit-to-stand tasks. Knowledge of these golf swing loads can help both the clinician and golf professional provide better evidence-based advice to golfers in order to keep them healthy and avoid future pain/injury.

Thin-walled cylindrical shells in engineering designs and critical infrastructures: A systematic review based on the loading response

Abstract Cylindrical shell structures are ubiquitous and essential supporting structures in various engineering applications. The aim of this research work is to provide a comprehensive overview of the behavior of cylindrical shell structures under different loading conditions, including external pressure, axial compression, and bending moment. The study found that the behavior of cylindrical shells was affected by their geometry, including diameter, length, thickness, and imperfections. These factors should be carefully considered in the design and analysis of cylindrical shells. Additionally, stiffeners and sandwich structures can be applied to improve the structural performance of cylindrical shells under different loading conditions. The work also highlighted the latest research trends in the field, such as the use of advanced materials, and numerical simulations to improve the understanding and design of cylindrical shell structures. Overall, this study has provided a valuable resource for engineers and researchers working on cylindrical shell structures, helping them to design and analyze the cylindrical shell structures more efficiently and effectively.

Can exercise interventions reduce external knee adduction moment during gait? A systematic review and meta-analysis

BackgroundAn increased external knee adduction moment has been identified as a factor contributing to the progression of medial knee osteoarthritis. Interventions that reduce knee adduction moment may help prevent knee osteoarthritis onset and progression. While exercise interventions have been commonly used to treat knee osteoarthritis, whether exercises can modulate knee adduction moment in knee osteoarthritis patients remains unknown. This systematic review and meta-analysis aimed to determine if exercise interventions are effective in reducing knee adduction moment during gait. MethodsStudy reports published through May 2023 were screened for pre-specified inclusion/exclusion criteria. Nine studies met the eligibility criteria and yielded 24 effect sizes comparing the reduction in knee adduction moment of the exercise intervention groups to the control groups. Moderator/experimental variables concerning characteristics of the exercise interventions and included subjects (e.g., sex, BMI, type of exercise, muscle group targeted, training volume, physical therapist supervision) that may contribute to variation among studies were explored through subgroup analysis and meta-regression. FindingsThe effect of exercise intervention on modulating knee adduction moment during gait was no better than control (ES = -0.004, P = 0.946). Sub-group analysis revealed that the effect sizes of studies containing only females (positive exercise effect) were significantly greater than studies containing both males and females. InterpretationExercise may not be effective in reducing knee adduction moment during gait. Clinicians aiming to decrease knee adduction moment in patients with medial knee osteoarthritis should consider alternative treatment options. Exploring the underlying mechanism(s) regarding a more positive response to exercises in females may help design more effective exercise interventions.

Subsequent Jumping Increases the Knee and Hip Abduction Moment, Trunk Lateral Tilt, and Trunk Rotation Motion During Single-Leg Landing in Female Individuals.

Single-leg landings with or without subsequent jumping are frequently used to evaluate landing biomechanics. The purpose of this study was to investigate the effects of subsequent jumping on the external knee abduction moment and trunk and hip biomechanics during single-leg landing. Thirty young adult female participants performed a single-leg drop vertical jumping (SDVJ; landing with subsequent jumping) and single-leg drop landing (SDL; landing without subsequent jumping). Trunk, hip, and knee biomechanics were evaluated using a 3-dimensional motion analysis system. The peak knee abduction moment was significantly larger during SDVJ than during SDL (SDVJ 0.08 [0.10]N·m·kg-1·m-1, SDL 0.05 [0.10]N·m·kg-1·m-1, P = .002). The trunk lateral tilt and rotation angles toward the support-leg side and external hip abduction moment were significantly larger during SDVJ than during SDL (P < .05). The difference in the peak hip abduction moment between SDVJ and SDL predicted the difference in the peak knee abduction moment (P = .003, R2 = .252). Landing tasks with subsequent jumping would have advantages for evaluating trunk and hip control as well as knee abduction moment. In particular, evaluating hip abduction moment may be important because of its association with the knee abduction moment.

Influence of time from injury to surgery on knee biomechanics during walking in patients with anterior cruciate ligament reconstruction

ABSTRACT The pilot study aimed to determine whether the time from injury to surgery influences on postoperative knee biomechanics during walking in patients with anterior cruciate ligament reconstruction (ACLR). Thirty-two patients with unilateral ACLR (early, 10 patients; delayed, 22 patients) and 30 control subjects participated in this study. All examinations for patients with ACLR were performed preoperatively and at 12 months postoperatively and comprised passive knee joint laxity, knee muscle strength, and knee kinematics and kinetics during walking. At both time points, there were no significant differences in passive knee joint laxity and knee muscle strength between the early ACLR and delayed ACLR groups. Preoperatively, both the early ACLR and delayed ACLR patients exhibited significantly reduced knee extension movement from midstance to terminal stance compared to the control subjects. Moreover, the delayed ACLR patients exhibited significantly decreased peak external knee flexion moment compared to the control subjects. At 12 months postoperatively, the early ACLR patients showed significant improvement in knee extension movement from midstance to terminal stance compared to pre-ACLR, while the delayed ACLR patients did not show significant improvement in this knee extension movement. It can be concluded that early ACLR may be more beneficial to improve knee biomechanics during walking.

The influence of step width on balance control and response strategies during perturbed walking in healthy young adults

Individuals with neuromuscular deficits often walk with wider step widths compared to healthy adults. Wider steps have been linked to a higher destabilizing frontal-plane external moment and greater range of frontal-plane whole-body angular momentum (HR), which is an indicator of decreased balance control. The purpose of this study was to experimentally determine 1) how step width alters balance control during steady-state walking, and 2) if step width changes the balance response strategies following mediolateral surface perturbations in healthy adults.Fifteen healthy young adults (7 male, age: 25 ± 4 years) walked on an instrumented treadmill at narrow, self-selected, wide and extra-wide step widths. During perturbed trials, the treadmill provided random mediolateral surface translations to each foot midway through single-leg-stance. Muscle electromyography, biomechanical measures (HR, frontal-plane external moment and joint moments) and deviations (differences in these measures between the perturbed and unperturbed walking trials) were compared across step widths.During steady state walking, wider steps were associated with decreased balance control. Increasing step widths were also associated with increased gluteus medius activity and reduced hip abduction and ankle inversion moments, which suggests healthy subjects rely more on a lateral ankle strategy to maintain balance at increasing step widths. There was no change in the plantarflexion moment. During perturbed walking, lateral, but not medial, surface translations adversely affected balance control. Further, wider steps did not change the balance response strategies following the perturbations, which suggests healthy individuals have the capacity to respond similarly to the perturbations at different step widths.

Simulated Increase in Monoarticular Hip Muscle Strength Reduces the First Peak of Knee Compression Forces During Walking.

Reducing compressive knee contact forces (KCF) during walking could slow the progression and reduce symptoms of knee osteoarthritis. A previous study has shown that compensating for the hip flexion/extension moment could reduce the KCF peak occurring during early stance (KCFp1). Therefore, this study aimed to identify if monoarticular hip muscle could allow this compensation while considering different walking strategies. Gait trials from 24 healthy participants were used to make musculoskeletal models, and five load-cases were examined: (I) Normal, (II) with an applied external moment compensating for 100% of the hip flexion/extension moment, and (III-V) three conditions with isolated/combined 30% increase of peak isometric strength of gluteus medius and maximus. Knee contact forces, hip muscle forces, and joint moments were computed. A cluster analysis of the Normal condition was performed with hip and knee flexion/extension moment during KCFp1 as input to examine the influence of different walking strategies. The cluster analysis revealed two groups having significantly different hip and knee moments in early-stance (p < 0.01). The reduction in KCFp1 from the Normal condition, although present in both groups, was greater for the group with the highest hip and lowest knee flexion/extension moments for all conditions tested (II: -21.82 ± 8.71% versus -6.03 ± 6.68%, III: -3.21 ± 1.09% versus -1.59 ± 0.96%, IV: -3.00 ± 0.89% versus -1.76 ± 1.04%, V: -6.12 ± 1.69 versus -3.09 ± 1.95%). This reduction in KCFp1 occurred through a shift in force developed by the hamstrings during walking (biarticular) to the gluteus medius and maximus (monoarticular), whose isometric strength was increased. The differences between the groups suggest that this reduction depends on the walking strategy.

Flexural tests on composite basement walls with socket-type shear connectors

The effect of a recently developed socket-type shear connector (SSC) on the flexural behaviour of a composite basement wall (CBW) was examined in this work. To this end, 12 CBWs composed of cast-in-place (CIP) piles fabricated with H-shaped steel beams or reinforcing steel plates were prepared by varying the arrangement and amount of SSCs. Two-point loading was applied to simply supported CBW specimens. The CBW specimens with more SSCs had a higher effective stiffness in the elastic state and higher moment capacity in the ultimate state, irrespective of the cross-sectional details of the CIP piles. These trends were particularly prominent when a reinforcing steel plate was used in the SSCs. The post-peak behaviour of the CBW specimens subjected to a simulated load with a negative external moment tended to be more ductile. Consequently, a higher degree of composite action was fully exerted on the CBWs with greater numbers of SSCs. Using established equations for the sectional details of CBWs with SSCs, the nominal partially composite to full composite flexural capacity ratios of the CBW specimens subjected to simulated loads with positive and negative external moments were calculated to be, respectively, 0.83 and 0.91 for 0.5ηsc and 0.79 and 0.90 for 0.75ηsc, where ηsc is the normalised shear connector capacity specified in ANSI/AISC 360-16.

Research on application of compliant control of smart meter box handling robot

To solve the problem that the intelligent meter box may collide in the transportation workflow, the paper studies the collision detection of the cooperative robot. Firstly, the architecture and mechanical structure of the collaborative robot intelligent meter box push–pull system is analyzed. Secondly, using the relationship between joint torque and selection LuGre model of joint friction modeling. The second-order external moment observer is constructed based on the robot’s dynamics and generalized momentum equation. Furthermore, the performance of the external moment observer is optimized, and the real-time performance and anti-interference ability of the collision detection algorithm is improved by introducing PD control and speed feedback control. Finally, the results of the designed experiments reveal that the collision detection functions are better realized using the generalized momentum observer method.

Paper 41: Increased Knee Valgus and Hip Adduction Moments after Hamstring Autograft compared to Quadriceps Autograft in Adolescents 6 Months after Anterior Cruciate Ligament Reconstruction

Objectives: Evidence is limited related to the effects of autograft type on functional performance during gait lab-based functional testing after ACL reconstruction (ACLR), especially the quadriceps autograft. The goal of this study was to compare biomechanical outcomes as measured by 3D motion analysis during the drop vertical test between quadriceps autograft with bone block (QB), quadriceps autograft without bone block (Q), hamstring autograft (HS), and bone-patellar tendon-bone autograft (BTB) six-months postoperatively in an adolescent population. We hypothesized that the quadriceps groups would demonstrate decreased knee extension moments as compared to the hamstring autograft group without other significant differences. Methods: Patients aged 8-18 years who underwent primary ACLR were included. Patients with previous history of ipsilateral knee surgery were excluded. Kinematic and kinetic data collected during a drop vertical jump test in a formal gait lab using a computerized video-based system (Motion Analysis Corp. CORTEX software) was collected six months after ACLR and compared to the uninjured contralateral limb. The Kruskal Wallis test and subsequent pairwise comparisons were carried out for each studied parameter. Primary outcomes included transverse plane hip power, hip internal rotation moment, knee valgus angles, and knee extensor moments between the graft types. Secondary outcomes included hip abduction moment, knee valgus moment, and knee external rotation moment. Results: A total of 155 subjects’ charts were included for review, with 54, 40, 35, and 26 subjects in the HS, QB, Q, and BTB groups respectively. There were no significant differences in terms of age, sex, or affected leg (p &gt; 0.1973). Athletic activity for each subject was also noted when appropriate, including soccer (37), basketball (34), and American football (30). The QB group had smaller knee extension moments maximums (-0.97 N*m/kg vs. -0.35 N*m/kg, p = 0.0323) and smaller knee extension moment averages (-0.12 N*m/kg vs. -0.03 N*m/kg, p = 0.0265) as compared to the HS group. The Q group demonstrated smaller knee extension moment averages (-0.13 N*m/kg vs. -0.03 N*m/kg, p = 0.459) as compared to the HS group. Analysis of secondary outcomes revealed that the HS group demonstrated larger knee valgus moments at initial contact (0.28 N*m/kg vs -0.35 N*m/kg, p = 0.0254) as compared to the Q group. The HS group demonstrated significantly larger hip adduction moment maximums (0.30 N*m/kg vs -0.04 N*m/kg, p = 0.0426) and smaller knee external rotation moment averages (-0.02 N*m/kg vs 0.02 N*m/kg, p = 0.0206) as compared to the QB group. No other secondary outcomes were statistically significant between any of the groups. Conclusions: The findings of this study suggest that the quadriceps autograft may confer improved knee coronal plane biomechanics in regard to ACL reinjury rates when compared to a hamstring autograft at 6 months after ACLR in adolescent patients performing a drop vertical jump. The hamstring autograft group was significantly associated with larger knee valgus moments at initial contact as compared to the quadriceps autograft without bone block and significantly larger hip adduction moments compared to the quadriceps autograft with bone block. Both quadriceps grafts were shown to demonstrate significantly decreased knee extension moments as compared to a hamstring autograft. Further long-term clinical studies may be useful in determining whether the apparent biomechanical differences seen between autograft types are correlated with reinjury rates.

Real-time ground reaction force and knee extension moment estimation during drop landings via modular LSTM modeling and wearable IMUs.

This work investigates real-time estimation of vertical ground reaction force (vGRF) and external knee extension moment (KEM) during single- and double-leg drop landings via wearable inertial measurement units (IMUs) and machine learning. A real-time, modular LSTM-based model with four sub-deep neural networks was developed to estimate the vGRF and KEM from wearable IMUs. Sixteen subjects wore eight IMUs on the chest, waist, right and left thighs, shanks, and feet and performed drop landing trials. Ground embedded force plates and an optical motion capture system were used to capture lower extremity biomechanics for model training and evaluation. During single-leg drop landings, accuracy for the vGRF and KEM estimation was R2=0.88 ±0.12 and R2=0.84 ±0.14, respectively, and during double-leg drop landings, accuracy for the vGRF and KEM estimation was R2=0.85 ±0.11 and R2=0.84 ±0.12, respectively. The best vGRF and KEM estimations of the model with the optimal LSTM unit number (130) require eight IMUs placed on the eight selected locations during single-leg drop landings. During double-leg drop landings, the best estimation on a leg only needs five IMUs placed on the chest, waist, and the leg's shank, thigh, and foot. The proposed modular LSTM-based model with optimally-configurable wearable IMUs can accurately estimate vGRF and KEM in real-time with relatively low computational cost during single- and double-leg drop landing tasks. This investigation could potentially enable in-field, non-contact anterior cruciate ligament injury risk screening and intervention training programs.