Joint Loading Research Articles

Facet joint loading after 1-, 2- and 3-level cervical disc arthroplasty: a comparison of spiked versus keeled baseplates

BackgroundThe purpose of this study was to examine facet contact forces above, below, and at surgical index levels induced by artificial disc implantation and compare the results from spiked versus keeled baseplates comprising the arthroplasty device. MethodsHuman specimens from C2 to C7 were subjected to flexion, extension, and lateral bending prior to, and following random allocation to spiked or keeled cervical arthroplasty at the index (C5-C6), inferior (C6-C7), and superior (C4-C5) levels. Thin film force sensors were inserted unilaterally into the corresponding facets prior to intact testing. Force data was normalized to the minimum forces recorded during each loading mode under each condition, reported as (Max/Min) force ratio and subjected to a 1-way ANOVA with Dunnett's post-hoc tests for comparison to intact specimens. ResultsUnder flexion, compared to intact, all levels displayed a significant reduction in force ratio following a 1- and 3-level implantation for the spiked baseplate device. An increase in force ratio was observed at the index level for a 2-level implantation but was mitigated with the completion of a superior device insertion. No statistical differences were noted for keeled devices. In extension, the spiked baseplate device reduced the force ratio for 1- and 2-level implantations. A 3-level insertion did not alter facet force ratios. For the keeled device, no statistical changes were noted. Lateral bending associated with spiked devices resulted in statistically reduced or nonsignificant changes in facet loading ratios. The keeled devices did not display significant changes to facet force ratios. ConclusionsImplantation of multilevel disc devices can reduce or sustain unaltered facet loading conditions. In general, 3-level arthroplasty statistically reduced or does not increase facet force ratios compared to intact values. The use of spiked versus keel device baseplates is a clinical selection involving anterior/posterior placement and endplate degeneration conditions.

Increasing the efficiency of the furnace depending on the operating conditions of the furnaces. Part 2. The technology of joint loading of lumpy anthracite and fluxed local specs

Increasing the efficiency of the furnace depending on the operating conditions of the furnaces. Part 2. The technology of joint loading of lumpy anthracite and fluxed local specs

Mechanical loading and orthobiologic therapies in the treatment of post-traumatic osteoarthritis (PTOA): a comprehensive review.

The importance of mechanical loading and its relationship to orthobiologic therapies in the treatment of post-traumatic osteoarthritis (PTOA) is beginning to receive attention. This review explores the current efficacy of orthobiologic interventions, notably platelet-rich plasma (PRP), bone marrow aspirate (BMA), and mesenchymal stem/stromal cells (MSCs), in combating PTOA drawing from a comprehensive review of both preclinical animal models and human clinical studies. This review suggests why mechanical joint loading, such as running, might improve outcomes in PTOA management in conjunction with orthiobiologic administration. Accumulating evidence underscores the influence of mechanical loading on chondrocyte behavior and its pivotal role in PTOA pathogenesis. Dynamic loading has been identified as a key factor for optimal articular cartilage (AC) health and function, offering the potential to slow down or even reverse PTOA progression. We hypothesize that integrating the activation of mechanotransduction pathways with orthobiologic treatment strategies may hold a key to mitigating or even preventing PTOA development. Specific loading patterns incorporating exercise and physical activity for optimal joint health remain to be defined, particularly in the clinical setting following joint trauma.

Fluoroscopy: Taking a closer look at joint motion in osteoarthritis

BackgroundKnowledge of joint biomechanics is crucial for understanding the pathophysiology of osteoarthritis (OA). Biomechanical changes, especially in early-stage OA, are subtle and therefore require highly accurate and precise ways of measuring joint loading (i.e., forces) and kinematics (i.e., motion). Most OA research investigating kinematics to date using conventional measurement methods, has been restricted either to measures of functional, weight-bearing activities with limited precision, or to highly precise measures of non-functional activities. X-ray fluoroscopy, however, is a medical imaging modality that can be used to precisely measure high-speed dynamic human movement in vivo under weight-bearing conditions. ObjectiveTo illustrate the potential of fluoroscopy to measure human movement and study joint biomechanics in OA by highlighting several exemplary applications in studies on knee OA. DesignWe searched PubMed to identify a selection of relevant studies with fluoroscopic evaluation of joint mechanics in individuals with, or at risk of developing, knee OA. ResultsFluoroscopy has been utilized in biomechanical studies in populations with early stages of knee OA or at risk of developing knee OA, as well as in studies evaluating conservative treatment strategies for knee OA. Due to its ability to capture highly accurate and precise kinematic measures, fluoroscopy holds great promise in providing new insights in the role of biomechanics in OA pathogenesis. ConclusionsThe use of fluoroscopy in larger cohorts and longitudinal (interventional) studies may lead to more robust and generalizable results and could clarify the mediation pathways of joint biomechanics in the onset and progression of OA.

Modelling of Multi-Bolted Systems at the Pretension Stage – Part 1: Mechanical Characteristics of the Contact between the Joined Elements

The subject of the paper is the modelling of multi-bolted connections that are at the pretensioning stage. Taking a systematic approach to the modelling issue, the connection was treated as a composite of four subsystems: a bolt set, a pair of joined elements and a contact layer between them. The first part of the paper describes experimental studies to determine the contact stiffness of a pair of elements separated from an exemplary asymmetric multi-bolted connection. The normal loading and unloading direction of the contact joint was considered. The tests were performed with the use of an INSTRON 8850 servo-hydraulic testing machine equipped with an extensometer. A normal stiffness characteristic in the form of an exponential function was proposed for the tested contact joint. It will be applied in the second part of the paper, in which finite element modelling of the multi-bolted connection will be presented.

Prediction of joint moments from kinematics using machine learning in children with congenital talipes equino varus and typically developing peers

BackgroundUnderstanding joint loading and the crucial role of joint moments is essential for developing treatment strategies in gait analysis, which often requires the precise estimation of joint moments through an inverse dynamic approach. This process necessitates the use of a force plate synchronized with a motion capture system. However, effectively capturing ground reaction force in typically developing (TD) children and those with congenital talipes equino varus (CTEV) presents challenges, while the availability and high cost of additional force plates pose additional challenges. Therefore the study aimed to develop, train, and identify the most effective machine learning (ML) model to predict joint moments from kinematics for TD children and those with CTEV. MethodIn a study at the Gait Lab, 13 children with bilateral CTEV and 17 TD children underwent gait analysis to measure kinematics and kinetics, using a 12-camera Qualisys Motion Capture System and an AMTI force plate. ML models were then trained to predict joint moments from kinematic data as input. ResultsThe random forest regressor and deep neural networks (DNN) proved most effective in predicting joint moments from kinematics for TD children, yielding better results. The Random Forest regressor achieved an average r of 0.75 and nRMSE of 23.03 % for TD children, and r of 0.74 and 23.82 % for CTEV. DNN achieved an average r of 0.75 and nRMSE of 22.83 % for TD children, and r of 0.76 and nRMSE of 23.9 % for CTEV. ConclusionsThe findings suggest that using machine learning to predict joint moments from kinematics shows moderate potential as an alternative to traditional gait analysis methods for both TD children and those with CTEV. Despite its potential, the current prediction accuracy limitations hinder the immediate clinical application of these techniques for decision-making in a pediatric population.

Significant improvement in tensile shear properties of friction stir lap welded nano TiB2/2024 Al composite joints via a novel tool pin geometry design

A novel designed tool pin with two shoulders and pins (stepped pin, S-pin) was performed to fabricate the friction stir lap welded nano-TiB2/2024 Al composite joints for the interface migration optimization and tensile shear strength improvement purposes. Compared with the conventional tapered pin (T-pin) joints, broken and dispersedly distributed hook, significantly restrained cold lap were observed in the S-pin joints. Submicron or hundreds of nanometers grains were detected in the stir zone (SZ), which should be attributed to the existence of nano-TiB2 hindering the movement of grain boundaries and limiting the growth of recrystallized grains. A wedge-shaped microhardness distributions of the S-pin joints were found, which would be better for the joint bearing capacity. Tensile shear loads of the S-pin joints were much higher than those of the T-pin joints. The optimal average tensile shear strength, 7.3 kN or 484 N/mm, were obtained when the S-pin was performed, dominantly fracturing in the heat affected zone (HAZ) rather than the SZ.

Bridging the sim2real gap. Investigating deviations between experimental motion measurements and musculoskeletal simulation results-a systematic review.

Musculoskeletal simulations can be used to estimate biomechanical variables like muscle forces and joint torques from non-invasive experimental data using inverse and forward methods. Inverse kinematics followed by inverse dynamics (ID) uses body motion and external force measurements to compute joint movements and the corresponding joint loads, respectively. ID leads to residual forces and torques (residuals) that are not physically realistic, because of measurement noise and modeling assumptions. Forward dynamic simulations (FD) are found by tracking experimental data. They do not generate residuals but will move away from experimental data to achieve this. Therefore, there is a gap between reality (the experimental measurements) and simulations in both approaches, the sim2real gap. To answer (patho-) physiological research questions, simulation results have to be accurate and reliable; the sim2real gap needs to be handled. Therefore, we reviewed methods to handle the sim2real gap in such musculoskeletal simulations. The review identifies, classifies and analyses existing methods that bridge the sim2real gap, including their strengths and limitations. Using a systematic approach, we conducted an electronic search in the databases Scopus, PubMed and Web of Science. We selected and included 85 relevant papers that were sorted into eight different solution clusters based on three aspects: how the sim2real gap is handled, the mathematical method used, and the parameters/variables of the simulations which were adjusted. Each cluster has a distinctive way of handling the sim2real gap with accompanying strengths and limitations. Ultimately, the method choice largely depends on various factors: available model, input parameters/variables, investigated movement and of course the underlying research aim. Researchers should be aware that the sim2real gap remains for both ID and FD approaches. However, we conclude that multimodal approaches tracking kinematic and dynamic measurements may be one possible solution to handle the sim2real gap as methods tracking multimodal measurements (some combination of sensor position/orientation or EMG measurements), consistently lead to better tracking performances. Initial analyses show that motion analysis performance can be enhanced by using multimodal measurements as different sensor technologies can compensate each other's weaknesses.

Effect of occlusal contact on TMJ loading during occlusion: An in silico study

Alterations in occlusal features may have significant consequences, ranging from dental aesthetics to health issues. Temporomandibular joint disorders (TMDs) are often associated with joint overload, and the correlation between occlusal features and TMDs has been thoroughly discussed. In current work, we introduced a novel stomatognathic model that aligns well with in vivo experimental measurements, specifically designed to decouple the impact of occlusal contact and periodontal ligament (PDL) negative feedback on temporomandibular joint (TMJ) loading. Utilizing an in-silico approach, the simulation analysis included six symmetric occlusal contact scenarios. Furthermore, a biomechanical lever model was employed to clarify the mechanical mechanism and investigate the multi-factorial effects of TMJ overload. These findings indicate that anterior shifts in the occlusal centre lead to increased TMJ loading, particularly in occlusal contact cases with anteroposterior changes. Considering the symmetrical distribution of occlusal contact, mediolateral alterations had a more modest effect on TMJ loading. Additionally, potential negative feedback activated by principal strain of periodontal could not only alleviate joint load but also diminish occlusal force. These investigations enhance our understanding of the intricate interactions between masticatory muscles, occlusal forces, and joint contact forces, thereby providing motivation for future comprehensive studies on TMJ biomechanical overload.

Effect of different ulnar osteotomies on loading of the distal radioulnar joint: a finite element analysis

BackgroundUlnar impingement syndrome is a prevalent source of ulnar carpal pain; however, there is ongoing debate regarding the specific location of shortening, the method of osteotomy, the extent of shortening, and the resulting biomechanical alterations.MethodTo investigate the biomechanical changes in the distal radioulnar joint (DRUJ) resulting from different osteotomy methods, a cadaveric specimen was dissected, and the presence of a stable DRUJ structure was confirmed. Subsequently, three-dimensional data of the specimen were obtained using a CT scan, and finite element analysis was conducted after additional processing.ResultsThe DRUJ stress did not change significantly at the metaphyseal osteotomy of 2–3 mm but increased significantly when the osteotomy length reached 5 mm. When the osteotomy was performed at the diaphysis, the DRUJ stress increased with the osteotomy length, and the increase was greater than that of metaphyseal osteotomy. Stress on the DRUJ significantly increases when the position is changed to pronation dorsi-extension. Similarly, the increase in stress in diaphyseal osteotomy was greater than that in metaphyseal osteotomy. When the model was subjected to a longitudinal load of 100 N, neither osteotomy showed a significant change in DRUJ stress at the neutral position. However, the 100 N load significantly increased stress on the DRUJ when the position was changed to pronation dorsi-extension, and the diaphyseal osteotomy significantly increased stress on the DRUJ.ConclusionsFor patients with distal oblique bundle, metaphyseal osteotomy result in a lower increase in intra-articular pressure in the DRUJ compared to diaphyseal osteotomy. However, it is crucial to note that regardless of the specific type of osteotomy employed, it is advisable to avoid a shortening length exceeding 5 mm.

Changes in Lower-Extremity Gait Biomechanics Following High-Cadence Cycling.

We sought to investigate the lower-extremity biomechanics underlying increased gait velocity following high-cadence cycling. Ground reaction forces (GRF) and lower-extremity kinematics and kinetics were recorded as 15 healthy adults walked at a self-selected pace prior to and immediately following a 15 min bout of cycling at a cadence of 75 rotations per minute. Propulsive GRF and stance-phase peak dorsiflexion and knee extension angles increased, while peak plantarflexion and hip extension angles decreased. Swing-phase peak dorsiflexion, plantarflexion, knee flexion, and hip flexion angles increased, while peak knee extension angle decreased. Peak dorsiflexion, knee extension, and hip extension angular velocity also increased during swing. No changes in peak joint moments were observed; however, peak positive ankle, knee, and hip joint power generation increased following cycling. Completing high-cadence cycling improves gait velocity by increasing propulsive GRF; increasing joint angular velocity during the swing phase of gait for the ankle, knee, and hip; and increasing positive power production by the ankle, knee, and hip during the stance phase. Increased gait velocity post cycling exercise did not increase lower-extremity joint moments. Cycling may be a viable exercise-based modality for increasing gait velocity, especially in populations where gait ability or joint loading is of particular concern.

An update on clinical gait analysis : Current developments and applications

The objective acquisition and assessment of joint movements and loads using instrumented gait analysis has become an established tool in clinical diagnostics. In particular, marker-based 3D gait analyses make use of an increasingly comprehensive database for the assessment of orthopaedic or neurological questions. Based on this data and medical-scientific experience, increasingly reliable approaches and evaluation strategies are emerging, which also draw on methods from artificial intelligence and musculoskeletal modelling. This article focusses on marker-based gait analyses of the lower extremity (hip, knee, foot) and how these can be used in aclinically relevant way using current methods, e.g. for determining indications or optimization of surgical planning. Finally, current developments and applications by using alternative methods from sensor technology and optical motion capture will be briefly discussed.

The effect of football heading on sidestep cutting biomechanics

Heading is an integral part of football, with ~20 headers or aerial duels executed per game to intercept, pass or score. However, concerns have recently been raised about the potential short and long-term health impacts of repeated heading. There is evidence suggesting increased risks of sub-concussive trauma – head impacts that do not result in obvious symptoms of concussion but affect cognition and motor function (Montenigro et al., 2017, J Neurotra, 34, 328-340). Repeated heading has been demonstrated to alter brain-muscle communication and affect movement control (Parr et al., 2023, Front Hu Neuro, 17, 1145700) and mechanics of simple tasks such as jumping (Lapointe et al., 2018, Int J Psychophys, 132, 93-98). However, whether these observed cognition and motor impairments translate to the biomechanics of complex multidirectional sport-specific movements such as sidestep cutting is not known. This is an important area to understand because sidestep cutting, an acute change of direction which is ubiquitous in football, is an important performance-determining factor and also a common inciting event for lower-limb injuries (Alentorn-Geli et al., 2009, Knee Sur Sports Trauma, Arth, 17, 705-729) such as the anterior cruciate ligament (ACL) rupture. Due to its propensity to generate high multiplanar knee joint loading during the stance phase of the manoeuvre (Dempsey et al., 2009, Am J Sports Med, 37, 2194-2200), there are often high stresses on the lower limbs which can result in musculoskeletal injury. To date, a copious number of studies have analysed the biomechanics of the sidestep cutting manoeuvre, showing that knee loading is sensitive to the constraints and strategies used to manoeuvre (Dos’Santos et al., 2019, Strength Cond J, 41, 40-54). Accordingly, this present study aims to determine whether there is an effect of repeated heading on sidestep-cutting biomechanics and, if so, the nature of this effect. Participants (n=40) will perform reactive and pre-planned sidestep cutting manoeuvres before completing 15 virtual (n=20) or physical (n=20) ball-heading. They will then repeat the cutting tasks immediately after the bout of heading. Whole-body optical motion capture, ground reaction forces, tri-planar lower-limb joint angles and moments during the stance phase will be analysed to test the effects of football heading on sidestep cutting biomechanics. Results may indicate whether exposure to football heading is a potential risk factor for lower-limb/ACL injury and thus inform the development of training sessions, athlete monitoring, and organisational/national heading guidance and policy for matches and training.

Obesity, Metabolic Syndrome, and Osteoarthritis Require Integrative Understanding and Management.

Osteoarthritis (OA) is a progressive chronic disease affecting the articular joints, leading to pain and disability. Unlike traditional views that primarily link OA to aging, recent understanding portrays it as a multifactorial degenerative disease of the entire joint. Emerging research highlights metabolic and immune dysregulation in OA pathogenesis, emphasizing the roles of obesity, dyslipidemia, and insulin resistance in altering joint homeostasis. Recent studies have increasingly focused on the complex role of white adipose tissue (WAT) in OA. WAT not only serves metabolic functions but also plays a critical role in systemic inflammation through the release of various adipokines. These adipokines, including leptin and adiponectin, have been implicated in exacerbating cartilage erosion and promoting inflammatory pathways within joint tissues. The overlapping global crises of obesity and metabolic syndrome have significantly impacted joint health. Obesity, now understood to contribute to mechanical joint overload and metabolic dysregulation, heightens the risk of developing OA, particularly in the knee. Metabolic syndrome compounds these risks by inducing chronic inflammation and altering macrophage activity within the joints. The multifaceted effects of obesity and metabolic syndrome extend beyond simple joint loading. These conditions disrupt normal joint function by modifying tissue composition, promoting inflammatory macrophage polarization, and impairing chondrocyte metabolism. These changes contribute to OA progression, highlighting the need for targeted therapeutic strategies that address both the mechanical and biochemical aspects of the disease. Recent advances in understanding the molecular pathways involved in OA suggest potential therapeutic targets. Interventions that modulate macrophage polarization, improve chondrocyte function, or normalize adipokine levels could serve as preventative or disease-modifying therapies. Exploring the role of diet, exercise, and pharmacological interventions in modulating these pathways offers promising avenues for reducing the burden of OA. Furthermore, such methods could prove cost-effective, avoiding the increase in access to healthcare.

Application of Machine Learning Methods to Investigate Joint Load in Agility on the Football Field: Creating the Model, Part I.

Laboratory studies have limitations in screening for anterior cruciate ligament (ACL) injury risk due to their lack of ecological validity. Machine learning (ML) methods coupled with wearable sensors are state-of-art approaches for joint load estimation outside the laboratory in athletic tasks. The aim of this study was to investigate ML approaches in predicting knee joint loading during sport-specific agility tasks. We explored the possibility of predicting high and low knee abduction moments (KAMs) from kinematic data collected in a laboratory setting through wearable sensors and of predicting the actual KAM from kinematics. Xsens MVN Analyze and Vicon motion analysis, together with Bertec force plates, were used. Talented female football (soccer) players (n = 32, age 14.8 ± 1.0 y, height 167.9 ± 5.1 cm, mass 57.5 ± 8.0 kg) performed unanticipated sidestep cutting movements (number of trials analyzed = 1105). According to the findings of this technical note, classification models that aim to identify the players exhibiting high or low KAM are preferable to the ones that aim to predict the actual peak KAM magnitude. The possibility of classifying high versus low KAMs during agility with good approximation (AUC 0.81-0.85) represents a step towards testing in an ecologically valid environment.

Effect of hybridization and composite architecture symmetry in the bonded joint performance of jute/carbon fibre-reinforced composites

This study investigates the effect of hybridization and composite architecture symmetry in the bonded joint performance of jute/carbon fibre-reinforced composites. Jute and carbon fibre bidirectional fabrics were used as reinforcement fibres for interlaminar hybrid epoxy composite adherends. The effect of the number of carbon fibre layers (1 and 2) as well as layup symmetry on the mechanical performance of the bonded joints was studied by testing single lap joints (SLJs) bonded with two adhesive types (a structural ductile bi-component epoxy adhesive and a brittle one). It was found that the hybridization of jute fibre reinforced composites with carbon fibres significantly improved the bonded joint performance for all tested specimens, when compared to the neat jute fibre reinforced composites (maximum of approx. 69 %). However, when compared to the neat carbon fibre (CFRP) adherend joints, the hybrid jute/carbon adherend joint configurations studied here achieved up to approximately 94 % (ductile adhesive system) and 97 % (brittle adhesive system) of maximum joint load efficiency of the CFRP synthetic joint. The effect of composite architecture symmetry was more pronounced for the brittle adhesive joints, whereas the failure loads of the ductile adhesive joints exhibited a plateau-like trend (ductile adhesives accommodate better the bending moments during SLJ loading, while brittle adhesives are more sensitive to adherend stiffness). A jute/carbon fibre hybrid composite bonded structure presents a potentially cost-effective and efficient alternative for reducing the structural carbon footprint, without a significant compromise in mechanical properties.

Dome versus single-cut osteotomies for correction of long bone deformities—technical considerations

Corrective osteotomy allows to improve joint loading, pain and function. In complex deformities, the biggest challenge is to define the optimal surgical solution, while considering anatomical, technical and biomechanical factors. While the single-cut osteotomy (SCOT) and focal dome osteotomy (FDO) are well-established treatment options, their mathematical relationship remain largely unclear. The aim of the study was (1) to describe the close mathematical relationship between the SCOT and FDO and (2) to analyze and introduce a novel technique—the stepped FDO—as a modification of the classic FDO. The mathematical background and relationship of SCOT and FDO are described for the example of a femoral deformity correction and visualized using a 3D surface model taking into account the benefits for the clinical application. The novel modifications of the stepped FDO are introduced and its technical and clinical feasibility demonstrated. Both, SCOT and FDO, rely on the same deformity axis that defines the rotation axis k for a 3D deformity correction. To achieve the desired correction using a SCOT, the resulting cutting plane is perpendicular to k, while using a FDO will result in a cylindrical cut with a central axis parallel to k. The SCOT and FDO demonstrate a strong mathematical relation, as both methods rely on the same deformity axis, however, resulting in different cutting planes. These characteristics enable a complementary use when defining the optimal type of osteotomy. This understanding enables a more versatile planning approach when considering factors as the surgical approach, biomechanical characteristics of fixation or soft tissue conditions. The newly introduced stepped FDO facilitates an exact reduction of the bone fragments and potentially expands the clinical applicability of the FDO.

Numerical investigations of earthquake resilient beam‐to‐column joints with replaceable BRFCPs using different restraint plates

AbstractA replaceable buckling‐restrained flange cover plate (BRFCP) was previously proposed to improve seismic performance of beam‐to‐column joints. Quasi‐static tests were conducted to investigate the seismic performance of beam‐to‐column joints using three different formats of restraint plates for BRFCP: no restraint plate, separated restraint plate, and integral restraint plate. The test results showed that both separated and integral restraint plates restrained the core plate buckling under compression and increased the beam‐to‐column joints load resistances. This paper first validates finite element models (FEMs) using test results. Then the validated FEMs are used to investigate influences from different BRFCP design parameters (such as core plate thickness, restraint plate thickness and length, restraining gap size, and restraint plate blot prestress force) to the beam‐to‐column joint load–drift hysteretic responses. Finally, the paper proposes a design range of each investigated design parameter and a BRFCP design procedure.

Shoulder External Over Internal Rotation Ratio Is Related to Biomechanics in Collegiate Baseball Pitching.

Altering baseball pitching mechanics affects both performance and the risk of injury. The purpose of this study is to investigate the relationships of shoulder external over internal rotation ratio (SEIR) and other shoulder rotational properties during physical exam and biomechanics of pitching for 177 collegiate baseball pitchers. The shoulder range of motion was quantitatively measured using a custom-made wireless device. Pitching motion data were collected at 240Hz, and a custom program was created to calculate the throwing arm motion and loading during baseball pitching. Linear regression and analysis of variance tests were performed to investigate the relationships between the shoulder physical exam outcomes and throwing arm biomechanics. SEIR had significant correlations with shoulder horizontal adduction angle at foot contact, maximum shoulder external rotation angle, maximum shoulder linear velocity, and elbow angle at ball release. SEIR groups had significant differences in shoulder proximal force, adduction torque, internal rotation torque, and horizontal adduction torque, and in elbow medial force and varus torque. Glenohumeral internal rotation deficit and total rotational motion deficit had no relationships with throwing arm motions or joint loadings. Shoulder health should be monitored to improve understanding of pitching mechanics in collegiate baseball pitchers.

Evaluating the Repeatability of Musculoskeletal Modelling Force Outcomes in Gait among Chronic Stroke Survivors: Implications for Contemporary Clinical Practice

This study aims to evaluate the consistency of musculoskeletal modelling outcomes during walking in chronic post-stroke patients, focusing on both affected and unaffected sides. Understanding the specific muscle forces involved is crucial for designing targeted rehabilitation strategies to improve balance and mobility after a stroke. Musculoskeletal modelling provides valuable insights into muscle and joint loading, aiding clinicians in analysing essential biomarkers and enhancing patients’ functional outcomes. However, the repeatability of these modelling outcomes in stroke gait has not been thoroughly explored until now. Twelve post-stroke, hemiparetic survivors were included in the study, which consisted of a gait analysis protocol to capture kinematic and kinetic variables. Two generic full body MSK models—Hamner (Ham) and Rajagopal (Raj)—were used to compute joint angles and muscle forces during walking, with combinations of two muscle force estimation algorithms (Static Optimisation (SO) and Computed Muscle Control (CMC)) and different joint degrees-of-freedoms (DOF). The multiple correlation coefficient (MCCoef) was used to compute repeatability for all forces, grouped based on anatomical function. Regardless of models and DOFs, the mean minimum (0.75) and maximum (0.94) MCCoefs denote moderate-to-excellent repeatability for all muscle groups. The combination of the Ham model and SO provided the most repeatable muscle force estimations of all the muscle groups except for the hip flexors, adductors and internal rotators. DOF configuration did not generally affect muscle force repeatability in the Ham–SO case, although the 311 seemed to relate to the highest values. Lastly, the DOF setting had a significant effect on some muscle groups’ force output, with the highest magnitudes reported for the 321 and 322 of non-paretic and paretic hip adductors and extensors, knee flexors and ankle dorsiflexors and paretic knee flexors. The primary findings of our study can assist users in selecting the most suitable modelling workflow and encourage the widespread adoption of MSK modelling in clinical practice.