Joint Reaction Research Articles

Altering the strength of the muscles crossing the lower limb joints only affects knee joint reaction forces

BackgroundGeneric musculoskeletal models based on literature data are often used to estimate joint reaction forces (JRFs) that otherwise could only be measured invasively. Estimated JRFs are sensitive to changes in maximum isometric force (Fiso) of the muscles, but these are normally simply scaled using a multiplicative coefficient. The impact of varying Fiso, or strength, of muscles crossing each lower limb joint on estimated JRFs has not been systematically explored in musculoskeletal models of the lower limb. Research QuestionHow do alterations in the strength of joint-crossing muscles influence the lower limb JRF magnitudes computed through a generic musculoskeletal model? MethodsBy modifying Fiso of muscles crossing hip, knee, ankle, or all joints at once up to ± 40% in 10% increments, thirty-two models were created to simulate the gait of a patient with an instrumented tibial prosthesis (5th Grand Challenge dataset). A standard workflow (inverse kinematics, static optimization, joint reaction analysis) was utilized to calculate JRFs. Both alterations in JRF magnitudes due to joint crossing muscles’ strength modifications and their accuracy against in vivo knee loading measurements were quantified. ResultsThe knee JRF was the most sensitive force to changes in the joint-crossing muscles’ strength (variations ranging from −37.9 ± 0.5% to +37.9 ± 3.2%), while the hip and ankle JRFs were almost unaffected (maximum variation: +6.1%). Reducing the strength of knee and ankle-crossing muscles and intensifying the strength of hip-crossing muscles lowered the knee JRF. The knee JRF was best estimated (peak error: 0.42 ± 0.15 body weight, root mean squared error: 0.37 ± 0.06 body weight, coefficient of determination: 0.76 ± 0.10) by the model with -40% weakened knee-crossing muscles. SignificanceAltering strengths mainly affects knee JRF estimated with generic musculoskeletal models, suggesting that personalization of strength of joint-crossing muscles is required for accurate knee JRF estimations. Rehabilitation regimes meant to strengthen muscles crossing a joint should be carefully designed to avoid undesired effects on the other joints.

Effect of two types of shoulder prosthesis on the muscle forces using a generic multibody model for different arm motions

BackgroundThis study aims to analyze the effects of a novel dual-bearing shoulder prosthesis and a conventional reverse shoulder prosthesis on the deltoid and rotator cuff muscle forces for four different arm motions. The dual-bearing prosthesis is a glenoid-sparing joint replacement with a moving center of rotation. It has been developed to treat rotator cuff arthropathy, providing an increased post-operative functionality.MethodsA three-dimensional musculoskeletal OpenSim® model of an upper body, incorporating a natural gleno-humeral joint and a scapula-thoracic joint developed by Blana et al. (J Biomech 41: 1714-1721, 2008), was used as a reference for the natural shoulder. It was modified by integrating first a novel dual-bearing prosthesis, and second, a reverse shoulder prosthesis into the shoulder joint complex. Four different arm motions, namely abduction, scaption, internal and external rotation, were simulated using an inverse kinematics approach. For each of the three models, shoulder muscle forces and joint reaction forces were calculated with a 2 kg weight in the hand.ResultsIn general, the maximal shoulder muscle force and joint reaction force values were in a similar range for both prosthesis models during all four motions. The maximal deltoid muscle forces in the model with the dual-bearing prosthesis were 18% lower for abduction and 3% higher for scaption compared to the natural shoulder. The maximal rotator cuff muscle forces in the model with the dual-bearing prosthesis were 36% lower for abduction and 1% higher for scaption compared to the natural shoulder. Although the maximal deltoid muscle forces in the model with the dual-bearing prosthesis in internal and external rotation were 52% and 64% higher, respectively, compared to the natural shoulder, the maximal rotator cuff muscle forces were 27% lower in both motions.ConclusionThe study shows that the dual-bearing shoulder prosthesis is a feasible option for patients with rotator cuff tear and has a strong potential to be used as secondary as well as primary joint replacement. The study also demonstrates that computer simulations can help to guide the continued optimization of this particular design concept for successful clinical outcomes.

Inter-Rater Reliability of Clinical Testing for Laxity After Knee Arthroplasty

BackgroundThe clinical examination for laxity has been considered a mainstay in evaluation of the painful knee arthroplasty, especially for the diagnosis of instability. More than 10 mm of anterior-posterior (AP) translation in flexion has been described as important in the diagnosis of flexion instability. The inter-observer reliability of varus/valgus and AP laxity testing has not been tested. MethodsTen subjects with prior to total knee arthroplasty (TKA) were examined by 4 fellowship-trained orthopedic knee arthroplasty surgeons. Each surgeon evaluated each subject in random order and was blinded to the results of the other surgeons. Each surgeon performed an anterior drawer test at 30 and 90 degrees of flexion and graded the instability as 0-5 mm, 5-10 mm or >10 mm. Varus-valgus testing was also graded. Motion capture was used during the examination to determine the joint position and estimate joint reaction force during the examination. ResultsInter-rater reliability (IRR) was poor at 30 and 90 degrees for both the subjective rater score and the measured AP laxity in flexion (k = 018-0.22). Varus-valgus testing similarly had poor reliability. Force applied by the rater also had poor IRR. ConclusionClinical testing of knee laxity after TKA has poor reliability between surgeons using motion analysis. It is unclear if this is from differences in examiner technique or from differences in pain or quadriceps function of the subjects. Instability after TKA should not be diagnosed strictly by clinical testing and should involve a complete clinical assessment of the patient.

Investigating acute changes in osteoarthritic cartilage by integrating biomechanics and statistical shape models of bone: data from the osteoarthritis initiative.

ObjectiveThis proof-of-principle study integrates joint reaction forces (JRFs) and bone shape to assess acute cartilage changes from walking and cycling.MethodsSixteen women with symptomatic knee osteoarthritis were recruited. Biomechanical assessment estimated JRFs during walking and cycling. Subsamples had magnetic resonance imaging (MRI) performed before and after a 25-min walking (n = 7) and/or cycling (n = 9) activity. MRI scans were obtained to assess cartilage shape and composition (T2 relaxation time). Bone shape was quantified using a statistical shape model built from 13 local participants and 100 MRI scans from the Osteoarthritis Initiative. Statistical parametric mapping quantified cartilage change and correlations between cartilage change with JRFs and statistical shape model features.ResultsCartilage thickness (interior lateral, Δ − 0.10 mm) and T2 (medial, Δ − 4 ms) decreased on the tibial plateau. On the femur, T2 change depended on the activity. Greater tibiofemoral JRF was associated with more cartilage deformation on the lateral femoral trochlea after walking (r − 0.56). Knees more consistent with osteoarthritis showed smaller decreases in tibial cartilage thickness.DiscussionWalking and cycling caused distinct patterns of cartilage deformation, which depended on knee JRFs and bone morphology. For the first time, these results show that cartilage deformation is dependent on bone shapes and JRFs in vivo.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10334-022-01004-8.

A Musculoskeletal Multibody Algorithm Based on a Novel Rheonomic Constraints Definition Applied to the Lower Limb.

In this paper, a multibody model was developed in the framework of biotribology of lower limb artificial joints. The presented algorithm performs the inverse dynamics of musculoskeletal systems with the aim to achieve a tool for the calculation of the joint reaction forces. The revolute joint, the cam joint, the spherical joint and the free joint were considered in the analyzed lower limb system by introducing a novel analytical formulation of the rheonomic constraint equations based on the quaternions theory. Within the kinematical analysis, the curved muscle paths were modeled by simulating their geodesic wrapping over bony surfaces while the muscle actuations were formulated through the Hill muscle model. The developed theoretical model was developed in matlab environment allowing to follow the classical musculoskeletal analysis pipeline: kinematical analysis, inverse dynamics, and static optimization, applied to the lower limb during the gait kinematics. The validation of the results was obtained by comparing the calculated hip joint reactions with the ones obtained in vivo by Bergmann and calculated by Opensim software, showing a satisfactory agreement. The proposed model and algorithm represent a fully open and controllable synovial joint tribological configuration generator tool, useful to be coupled with numerical lubrication/contact models in the framework of the in silico artificial joints tribological optimization.

Hybrid Predictive Model for Lifting by Integrating Skeletal Motion Prediction With an OpenSim Musculoskeletal Model.

In this study, a novel hybrid predictive musculoskeletal model is proposed which has both motion prediction and muscular dynamics assessment capabilities. First, a two-dimensional (2D) skeletal model with 10 degrees of freedom is used to predict a symmetric lifting motion, outputting joint angle profiles, ground reaction forces (GRFs), and center of pressure (COP). These intermediate outputs are input to the scaled musculoskeletal model in OpenSim for muscle activation and joint reaction load analysis. Finally, the experimental validation is carried out. Static Optimization tool is used to estimate the muscle activation data in OpenSim for the predicted lifting motion. Joint reaction forces of the lumbosacral joint (L5-S1) are generated using the OpenSim Joint Reaction analysis tool. The predicted joint angles, muscle activations, and peak joint reaction forces are compared with experimental data and data from literature to validate the hybrid model. The proposed hybrid model combines the skeletal model's rapid motion prediction with OpenSim's complex muscular dynamics assessment, and it can serve as a new generic tool for motion prediction and injury analysis in ergonomics and biomechanics.

FINITE ELEMENT ANALYSIS OF FEMORAL PROSTHESIS UNDER TRANSIENT LOADING FOR MULTIPLE ACTIVITIES OF DAILY LIVING

The femoral prostheses experience versatile loading during the activities of daily living (ADL) and subsequently encounter a variety of stresses. This paper presents a detailed finite element analysis (FEA) of the femoral implant under transient loading. The distinct loading patterns corresponding to the most commonly occurring ADL are utilized for simulating the different scenarios. The CT reconstructed CAD model of the human femur bone assembled with a femoral implant is utilized for this study. The loading scenarios for walking, stair ascent, stair descent, standing up, sitting down, standing on one leg and knee bending are simulated by using the joint reaction forces and moments, corresponding to a body weight of 750 N, for the FEA. The results of this study are validated using a preliminary in-house built experimental setup comprising a fixture for a stainless steel femoral implant with sensors attached at three locations on the implant. The results indicate that the highest stresses are generated in case of the stair descent, stair ascent and standing on a single leg type of activities. These activities that generate high stresses on the implant surfaces are not suitable for the longevity of the implant and are therefore not advisable for post-operative patients.

181 Can Movement Modelling Software, in a Digital Preclinical Trial, Help Understand the Optimal Sit to Stand Motion Using Commercially Available Peripheral Nerve Stimulators?

Abstract Aim Ethical approval is difficult to acquire for functional electrical stimulation trials, simulation may bridge the gap between FES concept and clinical trial approval. Using OpenSim modelling tool, this project aims to identify the minimum number of muscles, their strength and order of stimulation, that can produce the safest standing motion, using commercially available peripheral nerve stimulators. Method Modelling was executed using version 4.1 of OpenSim, utilising a previously validated, and extensively referred to, OpenSim lower limb model (Gait2354_Simbody) as the base model. Starting excitation values emulated previous literature for optimal sit to stand motion. EMG values were inputted using the excitation function of the forward dynamics tool, used to predict motion given defined neurological excitation values. Muscle groups and excitation values were altered iteratively to achieve the objective. Once the model performed the required function, within normal joint forces, the simulation was stopped. Results For optimal movement, the muscles required included, Gluteus Maximus, Rectus Femoris, Sartorius, Soleus, Tibialis Anterior, Vastus Intermedialis. This exceeded the 5-muscle objective, however muscles that shared a nervous supply could utilise a single FES port. Joint reaction forces remained within literature estimates, knee on tibia joint in the vertical plane achieved 2500N bilaterally, this represents a force equating to 3.64 times body weight. Conclusions Movement modelling software can become a fundamental tool in acquiring ethical approval for FES studies through simulation of full body motion. OpenSim requires iterative inputted improvements by the user, therefore a software which generates automated efficient movements would be more accurate and faster.

Femoral version deformities alter joint reaction forces in dysplastic hips during gait

Developmental dysplasia of the hip (DDH) causes hip instability and early-onset osteoarthritis. The focus on pathomechanics in DDH has centered on the shallow acetabulum, however there is growing awareness of the role of femoral deformities in joint damage. The objective of this study was to determine the influence of femoral version (FV) on the muscle and joint reaction forces (JRFs) of dysplastic hips during gait. Magnetic resonance images, in-vivo gait data, and musculoskeletal models were used to calculate JRFs and simulate changes due to varying FV deformities. Rotation about the long axis of the femur was added in the musculoskeletal models to simulate FV values from −5° (relative retroversion) to + 35° (increased anteversion). In our simulations, FV deformities caused the largest changes to the anteroposterior and resultant JRFs. From a normal FV of 15°, a 15° increase in femoral anteversion caused JRFs to be less posterior in early stance (Δ = 0.43 ± 0.22 xbodyweight) and more anterior in late stance (Δ = 0.60 ± 14 xbodyweight). Relative retroversion caused anteroposterior changes that were similar to anteversion in early stance but opposite in late stance. Resultant JRFs experienced the largest changes during late stance where anteversion raised the peak by 0.48 ± 0.15 xbodyweight and relative retroversion lowered the peak by 0.32 ± 0.30 xbodyweight. Increasing anteversion increased hip flexor and abductor muscle forces, which caused the changes in JRFs. Identifying how FV deformities influence hip joint loading can elucidate their role in the mechanisms of hip degeneration in patients with DDH.

Convolutional LSTM: a deep learning approach to predict shoulder joint reaction forces

We developed a Convolutional LSTM (ConvLSTM) network to predict shoulder joint reaction forces using 3D shoulder kinematics data containing 30 different shoulder activities from eight human subjects. We considered simulation outcomes from the AnyBody musculoskeletal model as the baseline force dataset to validate ConvLSTM model predictions. Results showed a good correlation (>80% accuracy, r ≥ 0.82) between ConvLSTM predicted and AnyBody estimated force values, the generalization of the developed model for novel task type (p-value = 0.07 ∼ 0.33), and a better prediction accuracy for the ConvLSTM model than conventional CNN and LSTM models.

Temporomandibular joint shape in anthropoid primates varies widely and is patterned by size and phylogeny.

The temporomandibular joint is the direct interface between the mandible and the cranium and is critical for transmitting joint reaction forces and determining mandibular range of motion. As a consequence, understanding variation in the morphology of this joint and how it relates to other aspects of craniofacial form is important for better understanding masticatory function. Here, we present a detailed three-dimensional (3D) geometric morphometric analysis of the cranial component of this joint, the glenoid fossa, across a sample of 17 anthropoid primates, and we evaluate covariation between the glenoid and the cranium and mandible. We find high levels of intraspecific variation in glenoid shape that is likely linked to sexual dimorphism and joint remodeling, and we identify differences in mean glenoid shape across taxonomic groups and in relation to size. Analyses of covariation reveal strong relationships between glenoid shape and a variety of aspects of cranial and mandibular form. Our findings suggest that intraspecific variation in glenoid shape in primates could further be reflective of high levels of functional flexibility in the masticatory apparatus, as has also been suggested for primate jaw kinematics and muscle activation patterns. Conversely, interspecific differences likely reflect larger scale differences between species in body size and/or masticatory function. Results of the covariation analyses dovetail with those examining covariation in the cranium of canids and may be indicative of larger patterns across mammals.

Reaction Forces and Flexion-Extension Moments Imposed on Functional Spinal Units With Constrained and Unconstrained In Vitro Testing Systems.

A mechanical goal of in vitro testing systems is to minimize differences between applied and actual forces and moments experienced by spinal units. This study quantified the joint reaction forces and reaction flexion-extension moments during dynamic compression loading imposed throughout the physiological flexion-extension range of motion. Constrained (fixed base) and unconstrained (floating base) testing systems were compared. Sixteen porcine spinal units were assigned to both testing groups. Following conditioning tests, specimens were dynamically loaded for 1 cycle with a 1 Hz compression waveform to a peak load of 1 kN and 2 kN while positioned in five different postures (neutral, 100% and 300% of the flexion and extension neutral zone), totaling ten trials per functional spinal unit (FSU). A six degree-of-freedom force and torque sensor was used to measure peak reaction forces and moments for each trial. Shear reaction forces were significantly greater (25.5 N-85.7 N) when the testing system was constrained compared to unconstrained (p < 0.029). The reaction moment was influenced by posture (p = 0.037), particularly in C5C6 spinal units. In 300% extension (C5C6), the reaction moment was, on average, 9.9 N·m greater than the applied moment in both testing systems and differed from all other postures (p < 0.001). The reaction moment error was, on average, 0.45 N·m at all other postures. In conclusion, these findings demonstrate that comparable reaction moments can be achieved with unconstrained systems, but without inducing appreciable shear reaction forces.

Elevated loading at the posterior acetabular edge of dysplastic hips during double-legged squat.

Hips with developmental dysplasia (DDH) are at a heightened risk of premature hip osteoarthritis, which is often expedited by mechanically induced articular tissue damage. A prevalent form of damage in DDH is labral tears caused by abnormal loading at the shallow acetabular edge. Although the majority of reported DDH-related labral tears occur in the antero-superior acetabulum, posterior labral tears are prevalent in individuals whose lifestyle involves frequent high hip flexion tasks such as squatting. To better understand region-specific risks for chondrolabral damage during high hip flexion, we used image-based musculoskeletal models to compare acetabular edge loading (AEL) during double-legged squat between hips with symptomatic DDH (n = 10) and healthy controls (n = 10). Compared to controls, hips with DDH had higher instantaneous posterior AEL at the lowest point of squat (2.6 vs. 1.8 ×BW, p ≤ 0.04), and higher accumulative loading across the duration of the squatting motion (2.6 vs. 1.9 ×BW*s, p ≤ 0.04). Elevated posterior AEL coincided with increased net hip extension moments and posterior joint reaction forces, and was correlated with the severity of DDH acetabular deformity. Our findings suggest that posterior AEL is elevated in hips with symptomatic DDH during double-legged squat, which may contribute to chondrolabral damage in individuals who often perform such high hip flexion tasks. Clinical evaluation of DDH should consider patient-specific anatomy and lifestyle factors when establishing diagnoses and planning personalized treatment.

Musculoskeletal modeling-based definition of load cases and worst-case fracture orientation for the design of clavicle fixation plates.

Mechanical performance of clavicle fracture fixation plates is often evaluated using finite element (FE) analysis. Typically, these studies use simplified loading conditions and assume a transversal fracture orientation. However, the loading conditions and fracture orientation influence how the fracture site and thus fixation plate is loaded. In this study, a musculoskeletal model that included the clavicle muscles and scapulohumeral rhythm was defined based on previously published models. The standard OpenSim workflow (inverse kinematics, inverse dynamics, static optimization, and joint reaction analysis) was used to calculate muscle and joint contact forces based on 3D marker data collected in three subjects during seven activities of daily living (ADL). These loading conditions were then applied to a 3D clavicle model with three different fracture orientations and the mean resulting moments on both fragments were calculated to assess fracture stability. Magnitude of glenohumeral contact forces showed good agreement with instrumented shoulder prosthesis data, whereas simulated muscle activations were comparable to experimental EMG data. An oblique fracture orienting from superomedial to inferolateral was the least self-stabilizing. The loading to which the clavicle is exposed during ADL tasks is more complex than the simplified loading conditions typically used as boundary conditions in FE analyses of clavicle fracture fixation plates. Additionally, transversal fractures did not represent the least self-stabilizing fracture orientation, and thus calculated stresses in the plate could be underestimated. Therefore, more complex loading conditions and evaluation of a midshaft fracture running from superomedial to inferolateral is more relevant in FE analyses of midshaft clavicle fracture fixation plates.

Sensitivity of musculoskeletal models to variation in muscle architecture parameters.

Musculoskeletal models, like all theoretical models of physical processes, depend on the assumptions needed to construct the model. For musculoskeletal models, these assumptions include, among other things, the kinematic data, the kinetic data and the muscle parameters. The former (dynamic) data can be acquired relatively easily from living subjects, but the latter are usually based on limited information, frequently determined from cadaver studies performed on elderly individuals. Previously, we determined the sensitivity of forces to dynamic differences among 10 humans walking on a straight path. Here, we assess the sensitivity of the muscle and joint reaction forces developed in human walking to variable muscle parameters obtained from 10 living adults, whose data were recently reported, and compared the results with the values from a standard model that depends on cadaveric data. We found that, while the force patterns across the stance cycle were similar among muscle parameter models, differences of as much as 15% in the force magnitude were produced. Whether or not the variation between the standard model and other muscle parameters is important depends on why the forces are required.

Potential Reduction of Joint Reaction Forces by Statically Balancing Serial Robots Using Zero-Free-Length Springs

Potential Reduction of Joint Reaction Forces by Statically Balancing Serial Robots Using Zero-Free-Length Springs

Motion is Maintained at the Tibial and Polyethylene Component Interface in a Mobile-Bearing Total Ankle Arthroplasty at Mid and Long-Term Follow-Up

Category:Ankle Arthritis; Ankle; HindfootIntroduction/Purpose:Normal biomechanics of the ankle joint includes sagittal motion, but also anterior-posterior (AP) translation (1mm) as well as axial rotation (5-8 degrees). Sagittal motion is well described in total ankle arthroplasty (TAA), however, current understanding of mobile-bearing motion at the tibial-polyethylene interface in TAA is limited to AP motion and short-term data on axial rotation. The purpose of our study was to determine if polyethylene components maintain mobility adjacent to the tibial component in mobile bearing TAA at mid and long-term follow-up in both the sagittal and axial planes in patients more than 48 months post-operatively.Methods:Patients who were a minimum of 48 months postoperative from a third-generation mobile-bearing TAAwere identified. Fluoroscopic images perpendicular to the tibial component were saved at maximum internal and external rotation on AP, and the lateral images were saved in maximum plantarflexion and dorsiflexion. Sagittal range of motion and AP translation of the polyethylene component were measured from the lateral images. Axial rotation was determined by measuring the relative position of the two wires within the polyethylene component on AP internal and external rotation imaging. This relationship was compared to a table previously developed from fluoroscopic images taken at standardized degrees of axial rotation of a nonimplanted polyethylene with the associated length relationship of the two imbedded wires. Total axial motion was determined by the difference between angle value determined for maximum internal and external rotation.Results:Eight patients were included in this investigation, 5 (62.5%) were female and average age was 72.6 (range, 59-83) years. Time from surgery averaged 94.2 (range, 54.7-118.6) months. Total sagittal range of motion between the talar and the polyethylene component averaged 20.3 (range, 10-30) degrees. All patients (100%) maintained motion at the tibia-polyethylene interface. Axial motion for total internal and external rotation of the polyethylene component articulation on the tibial component averaged 5.3 (range, 2-12) degrees. AP translation of the polyethylene component relative to the tibial component averaged 1.1 (range, 0.4-2.6) mm during plantarflexion and dorsiflexion. There was no relationship between axial rotation or AP translation of the polyethylene component and ankle joint range of motion (P >.05).Conclusion:To our knowledge, this is the first investigation to measure axial and sagittal motion of the polyethylene component in mobile bearing TAA at the tibial implant interface in patients at mid and long-term follow-up. Based on our results, motion is maintained an average of 8 years post-operatively and concludes that a mobile-bearing TAA has the potential to fall within the parameters of normal polyaxial ankle motion several years after implantation. Such maintenance of motion may have a positive influence on gait pattern, polyethylene wear, joint reaction forces and implant longevity.

Lower extremity joint reaction forces and plantar fascia strain responses due to incline and decline walking

Purpose: The present study aims to investigate the effect of incline and decline walking on ground and joint reaction forces (JRF) of lower extremity and plantar fascia strain (PFS) under certain surface inclination angles. Methods: Twenty-three male subjects walked on a customized platform with four different surface inclinations (i.e., 0, 5, 7.5 and 10°) with inclined and declined directions. The motion of the ten reflective markers was captured using Qualysis motion capture system (Qualysis, Gothenburg, Sweden) and exported to a visual three-dimensional (3D) software (C-motion, Germantown, USA) in order to analyze the GRF, JRF and PFS. Results: The results found that the peak vertical GRF is almost consistent for 0 and 5° inclination slope but started to decrease at 7.5° onwards during decline walking. The most affected JRF was found on knee at medial-lateral direction even as low as 5 to 10° inclination for both walking conditions. Furthermore, the findings also show that the JRF of lower extremity was more affected during declined walking compared to inclined walking based on the number of significant differences observed in each inclination angle. The PFS was found increased with the increase of surface inclination. Conclusions: The findings could provide a new insight on the relationship of joint reaction forces and strain parameter in response to the incline and decline walking. It would benefit in providing a better precaution that should be considered during hiking activity, especially in medial-lateral direction in order to prevent injury or fall risk.

The effect of biomechanical foot-based interventions on patellofemoral joint loads during gait in adults with and without patellofemoral pain or osteoarthritis: a systematic review protocol

BackgroundPatellofemoral pain is highly prevalent across the lifespan, and a significant proportion of people report unfavourable outcomes years after diagnosis. Previous research has implicated patellofemoral joint loading during gait in patellofemoral pain and its sequelae, patellofemoral osteoarthritis. Biomechanical foot-based interventions (e.g., footwear, insoles, orthotics, taping or bracing) can alter patellofemoral joint loads by reducing motions at the foot that increase compression between the patella and underlying femur via coupling mechanisms, making them a promising treatment option. This systematic review will summarise the evidence about the effect of biomechanical foot-based interventions on patellofemoral joint loads during gait in adults with and without patellofemoral pain and osteoarthritis.MethodsMEDLINE (Ovid), the Cumulative Index to Nursing and Allied Health Literature CINAHL, The Cochrane Central Register of Controlled Trials (CENTRAL), SPORTdiscus (EBSCO) and Embase (Ovid) will be searched. Our search strategy will include terms related to ‘patellofemoral joint’, ‘loads’ and ‘biomechanical foot-based interventions’. We will include studies published in the English language that assess the effect of biomechanical foot-based interventions on patellofemoral joint loads, quantified by patellofemoral joint pressure, patellofemoral joint reaction force and/or knee flexion moment. Two reviewers will independently screen titles and abstracts, complete full-text reviews, and extract data from included studies. Two reviewers will assess study quality using the Revised Cochrane Risk of Bias (RoB 2) tool or the Cochrane Risk Of Bias In Non-Randomized Studies – of Interventions (ROBINS-I) tool. We will provide a synthesis of the included studies’ characteristics and results. If three or more studies are sufficiently similar in population and intervention, we will pool the data to conduct a meta-analysis and report findings as standardised mean differences with 95% confidence intervals. If a meta-analysis cannot be performed, we will conduct a narrative synthesis of the results and produce forest plots for individual studies.DiscussionThis protocol outlines the methods of a systematic review that will determine the effect of biomechanical foot-based interventions on patellofemoral joint loads. Our findings will inform clinical practice by identifying biomechanical foot-based interventions that reduce or increase patellofemoral joint loads, which may aid the treatment of adults with patellofemoral pain and osteoarthritis.Trial registrationRegistered with PROSPERO on the 4th of May 2022 (CRD42022315207).

On the Miscibility of Nematic Liquid Crystals with Ionic Liquids and Joint Reaction for High Helical Twisting Power Product(s).

Mixtures of nematic liquid crystals (LCs) with chiral ionic liquids (CILs) may find application as active materials for electrically driven broadband mirrors. Five nematic liquid crystal hosts were mixed with twenty three ionic liquids, including chiral ones, and studied in terms of their miscibility within the nematic phase. Phase diagrams of the mixtures with CILs which exhibited twisted nematic phase were determined. Miscibility, at levels between 2 and 5 wt%, was found in six mixtures with cyanobiphenyl-based liquid crystal host—E7. On the other hand, the highest changes in the isotropization temperature was found in the mixtures with isothiocyanate-based liquid crystal host—1825. Occurrence of chemical reactions was found. A novel chiral binaphtyl-based organic salt [N11116][BNDP] was synthesized and, in reaction to the 1825 host, resulted in high helical twisting power product(s). Selectivity of the reaction with the isothiocyanate-based liquid crystal was found.