Biomechanical Aspects Research Articles

Root traits as drivers of plant and ecosystem functioning: current understanding, pitfalls and future research needs.

The effects of plants on the biosphere, atmosphere and geosphere are key determinants of terrestrial ecosystem functioning. However, despite substantial progress made regarding plant belowground components, we are still only beginning to explore the complex relationships between root traits and functions. Drawing on the literature in plant physiology, ecophysiology, ecology, agronomy and soil science, we reviewed 24 aspects of plant and ecosystem functioning and their relationships with a number of root system traits, including aspects of architecture, physiology, morphology, anatomy, chemistry, biomechanics and biotic interactions. Based on this assessment, we critically evaluated the current strengths and gaps in our knowledge, and identify future research challenges in the field of root ecology. Most importantly, we found that belowground traits with the broadest importance in plant and ecosystem functioning are not those most commonly measured. Also, the estimation of trait relative importance for functioning requires us to consider a more comprehensive range of functionally relevant traits from a diverse range of species, across environments and over time series. We also advocate that establishing causal hierarchical links among root traits will provide a hypothesis-based framework to identify the most parsimonious sets of traits with the strongest links on functions, and to link genotypes to plant and ecosystem functioning.

ОСОБЕННОСТИ РАЗВИТИЯ, РОСТА И СТРОЕНИЯ КОСТЕЙ СОБАК И КОШЕК

This article is devoted to the systematic and comparative aspects of the phylo - and ontogenetic development, growth and structure of the bones of dogs and cats. We know that bone (lat. os) is a solid organ of humans and vertebrates, consisting of several tissues, the most important of which is bone. The bone performs musculoskeletal and protective functions, is an integral part of the vertebrate endoskeleton, produces red and white blood cells, and stores minerals. Bone tissue is a type of dense connective tissue. Bones come in a wide variety of shapes and sizes, depending on the function of the particular bone. There are between 289 and 292 bones in the body of dogs and cats (a range of difference due to the diversity of the caudal vertebrae). Each has a complex structure, so that they are quite light, but at the same time rigid and durable. The bone may include in its structure: bone marrow, endosteum, periosteum, nerves, blood vessels, cartilage. Bones are made up of various bone tissue cells: osteoblasts are involved in the formation and mineralization of bones, osteocytes maintain structure, and osteoclasts provide bone resorption. The mineralized matrix of bone tissue has an organic component mainly from collagen and an inorganic component of bone tissue from various salts. Therefore, the coverage of the features of development, growth and structure of bones, as well as the role of bones in maintaining calcium homeostasis, blood supply and biomechanical aspects in cats and dogs, today is necessary for teachers, practitioners and students.

A review on biomechanics of the hallux valgus pathology and its surgical treatments

The present paper aims at an interdisciplinary field, regarding biomechanics aspects of the Hallux Valgus, which is a frequent deformity in our days. Owing to the importance of the study theme and the social impact, we consider it very important that the state of the art should be as detailed as possible, due to this condition being frequent in women and older people. The review will target recent research of the biomechanics of the foot, the test subjects being in normal conditions and also patients affected by Hallux valgus deformities; likewise, it will define important geometrical elements, which are required for the engineering approach of the issue. As well, the 3D modelling of the condition will be taken into consideration, beside with the surgical procedures and conservative treatments. Another important aspect covered in the paper is regarding the research and CAE simulations using the FEM, alongside with the work stands developed in this area. The bibliographic research found on the most important journals and databases shall be synthesized and structured in order to highlight the big picture of a specific research regarding a future PhD thesis.

Correlational anatomy of biceps brachii muscle with its footprint and aponeurosis parameters

Background: The anatomy of the distal biceps tendon (DBT) and its insertional anatomy to radial tuberosity is important to understand the pathophysiology of tendon rupture and in surgical repair of the ruptured tendon. The present study aimed to evaluate the relationship between biceps brachii parameters with biceps footprint and lacertus fibrosus (LF) parameters. Methodology: This was a cross-sectional observational study done on 23 cadavers. The biceps brachii perimeters, the length of the DBT, distance between the radial head and radial tuberosity, footprint length, footprint breadth, and LF width were noted (with measuring tape and digital vernier caliper. LF angle was measured using Image J software. Results: There was a weak positive correlation between biceps brachii perimeter and footprint length (r = 0.392), biceps brachii perimeter and footprint breadth (r = 0.341), biceps brachii perimeter and LF width (r = 0.300), and moderate positive correlation between footprint length and breadth (r = 0.686). Conclusion: The biceps brachii perimeter has a minimal role in influencing the footprint dimensions and LF morphology. The study has explored the biomechanical aspect of the biceps brachii insertional anatomy. The data on footprint dimension and aponeurosis could help the surgeons in the effective repair of the ruptured tendon and achieving a better postoperative outcome.

Biomechanical aspects of static foot load in physically active and inactive students

Introduction. This study investigated the parameters of foot load, as one of the dimensions of foot biomechanics, using a new method of objectification of the measured values. The examined biomechanical parameters directly affect correct gait and posture. The aim of this research was to determine if there was a statistically significant difference in the forefoot and rearfoot load, as well as the load on the whole foot between physically active and inactive students. Material and Methods. The study included 91 students, of whom 44 were physically inactive and 47 were physically active. Measurements were performed by using a baropodometry platform (FreeMed Maxi, Sensor Medica, Rome, Italy) used for the first time in our population for objectification of the morpho-physiological parameters. All reference values were provided by the manufacturer as a part of the Freestep version 1.4.01 software. Results. Our results showed that physically active students have statistically significantly higher forefoot load values. Physically inactive students have statistically significantly higher rearfoot load values. Also, physically inactive students have statistically significantly higher deviations in most parameters from the reference values compared to physically active students. The percentage of physically inactive students with non-physiological values is higher in every parameter compared to the percentage of physically active students. However, this difference is statistically significant only for the load on the right forefoot in relation to both feet. Conclusion. Physically active students showed a physiologically better foot load distribution than physically inactive students.

Results of stress-strain states study in prosthetics of different types of atrophy of edentulous mandible

Complete dentures remain still popular due to the economic component of such prosthetic treatment. However, additional fixation on intraosseous implants provides a greater clinical and functional effectiveness and a greater level of satisfaction with the results of prosthetics in edentulous patients. At the moment, the biomechanical aspects of complete denture prosthetics and prosthetics with fixation on implants, taking into account the degree of atrophy of the edentulous jaws, are not complete understood. Such studies make it possible to create recommendations on the choice of prosthetic tactics for edentulous patients. The aim of the research was to study the distribution of stress-strain states in prosthetics of the edentulous mandible with complete dentures and with designs supported on intraosseous implants, taking into account the type of atrophy. It was carried out computer simulation of 8 virtual finite element models of mandible with different types of atrophy. According to Keller they were 4 models: of the biomechanical system simulation "complete denture – mandible" and 4 ones – "denture – intraosseous implants – mandible". In each of the models, a chewing load of 100 N was simulated (symmetrically and asymmetrically). The ANSIS 12.1 finite element analysis was used to calculate the stress-strain states in the described calculation systems. It was estimated the distribution of stresses in cortical bone and displacements of the dentures on the prosthetic bed. Under using complete dentures, the maximum stresses in the bone tissue of the prosthetic bed were observed for the third type of mandible atrophy with all types of power load, the smallest ones – for the fourth type. Additional fixation of removable dentures in simulation models of biomechanical systems “denture – intraosseous implants – mandible” lead to a significant increase in stresses in the alveolar bone. The maximum stresses were observed in the area of the marginal bone, while their greatest values were in the well-expressed alveolar part of the mandible for first and third types by Keller. The movements of bases of complete dentures were insignificant and fluctuated within hundredths of a millimeter for all types of atrophy. The use of intraosseous implants for fixation of dentures caused increase in movements by several times. Besides, displacement fields were characteristic: they were uniform for complete dentures but in the use of implants – not. The expressed alveolar process in the first and third types of atrophy of the edentulous mandible caused an increase in the displacements of the distal sections of the dentures on both sides with a symmetrical force load and on one side – with an asymmetric one. It can be assumed that such a distribution of stress-strain states accelerates atrophy of prosthetic bed tissues. As a result of prosthetics of complete defects of lower dentitions, both with traditional complete dentures and with additional support on implants, different distribution of stress-strain states occurs in different phases of the chewing act in the bone of the prosthetic bed, the character of which is determined by the shape of the alveolar part described by Keller's classification. The results allow us to develop an algorithm for determining the kind of prosthetics for edentulous patients, depending on the type of mandible atrophy.

Biomechanical aspects of Tai Chi Chuan countermeasure against health threats during spaceflight

In support of NASA’s plan to establish human settlements on the Moon and Mars in the near future and the emergence of cutting-edge artificial intelligence as a tool for better health care, we look for ways to help astronauts stay physically and mentally healthy during a long and stressful trip. After reviewing existing aerobic and strength exercise methods available to astronauts, we propose that traditional Tai Chi Chuan (TCC) or Taijiquan can serve as a non-invasive intervention to help astronauts maintain physical and physiological integrity and cope with the impact of microgravity during and after spaceflights. Biomechanical aspects of TCC in terms of neuromuscular and musculoskeletal conditions are presented based on a review of evidence from the scientific literature that defines physiological responses associated specifically with the practice of TCC as relevant to space mission-related effects of microgravity on human physiology. This article provides a comprehensive review and description of the TCC biomechanics and their health influences in microgravity. The mysterious Chi (or Qi) of TCC is scientifically defined as kinesthetic sensations of position, movement, and force of muscles, tendons, and joints throughout body segments in kinetic chain motions. These sensations can be used to judge the correctness of TCC trainings as a countermeasure against microgravity to improve proprioception, kinesthesia, and mind-body coordination for astronauts. This study has far-reaching implications for the integration of TCC practices in complement with the effectiveness of existing countermeasure approaches, and provides direction for future research that might bridge the knowledge gap in improving exercise countermeasures for human spaceflight.

Mechanical Immunoengineering of T cells for Therapeutic Applications.

T cells, a key component in adaptive immunity, are central to many immunotherapeutic modalities aimed at treating various diseases including cancer, infectious diseases, and autoimmune disorders. The past decade has witnessed tremendous progress in immunotherapy, which aims at activation or suppression of the immune responses for disease treatments. Most strikingly, cancer immunotherapy has led to curative responses in a fraction of patients with relapsed or refractory cancers. However, extending those clinical benefits to a majority of cancer patients remains challenging. In order to improve both efficacy and safety of T cell-based immunotherapies, significant effort has been devoted to modulating biochemical signals to enhance T cell proliferation, effector functions, and longevity. Such strategies include discovery of new immune checkpoints, design of armored chimeric antigen receptor (CAR) T cells, and targeted delivery of stimulatory cytokines and so on.Despite the intense global research effort in developing novel cancer immunotherapies, a major dimension of the interactions between cancer and the immune system, its biomechanical aspect, has been largely underappreciated. Throughout their lifecycle, T cells constantly survey a multitude of organs and tissues and experience diverse biomechanical environments, such as shear force in the blood flow and a broad range of tissue stiffness. Furthermore, biomechanical properties of tissues or cells may be altered in disease and inflammation. Biomechanical cues, including both passive mechanical cues and active mechanical forces, have been shown to govern T cell development, activation, migration, differentiation, and effector functions. In other words, T cells can sense, respond to, and adapt to both passive mechanical cues and active mechanical forces.Biomechanical cues have been intensively studied at a fundamental level but are yet to be extensively incorporated in the design of immunotherapies. Nonetheless, the growing knowledge of T cell mechanobiology has formed the basis for the development of novel engineering strategies to mechanically modulate T cell immunity, a nascent field that we termed "mechanical immunoengineering". Mechanical immunoengineering exploits biomechanical cues (e.g., stiffness and external forces) to modulate T cell differentiation, proliferation, effector functions, etc., for diagnostic or therapeutic applications. It provides an additional dimension, complementary to traditional modulation of biochemical cues (e.g., antigen density and co-stimulatory signals), to tailor T cell immune responses and enhance therapeutic outcomes. For example, stiff antigen-presenting matrices have been shown to enhance T cell proliferation independently of the intensity of biochemical stimulatory signals. Current strategies of mechanical immunoengineering of T cells can be categorized into two major fields including passive mechanical cue-oriented and active force-oriented strategies. In this Account, we first present a brief overview of T cell mechanobiology. Next, we summarize recent advances in mechanical immunoengineering, discuss the roles of chemistry and material science in the development of these engineering strategies, and highlight potential therapeutic applications. Finally, we present our perspective on the future directions in mechanical immunoengineering and critical steps to translate mechanical immunoengineering strategies into therapeutic applications in the clinic.

Biomechanical Particularities in the Therapy of the Rheumatic Knee

In rheumatoid arthritis, the joints of the lower extremities are almost always affected. This is most conspicuous in the knee joint. In rheumatics, inflammatory osteoarthritis manifests itself comparably earlier than in patients with osteoarthritis. The focus of attention was primarily on the synovia with its destruction process and secondary changes. Now, driven by experimental research, dendritic cells and fibroblasts and molecular features are moving into the clinician’s field of vision. Even in joints that appear to be in remission with no swelling or pain, the activity of these cells leads to changes in the capsule-ligaments. The complex deformities and instabilities caused by this, in conjunction with atrophy of the inter-articular musculature, have an impact on the activities of daily life (ADL). If these biomechanical aspects of the knee joint are not taken into account early on in therapy, the frequency of primary and secondary surgical treatment increases. The timely recognition of biomechanical pathologies and consistent treatment can contribute to improving the patient situation in addition to adequate medication therapy.

ZIF-8 Modified Polypropylene Membrane: A Biomimetic Cell Culture Platform with a View to the Improvement of Guided Bone Regeneration.

PurposeDespite the significant advances in modeling of biomechanical aspects of cell microenvironment, it remains a major challenge to precisely mimic the physiological condition of the particular cell niche. Here, the metal–organic frameworks (MOFs) have been introduced as a feasible platform for multifactorial control of cell-substrate interaction, given the wide range of physical and mechanical properties of MOF materials and their structural flexibility.ResultsIn situ crystallization of zeolitic imidazolate framework-8 (ZIF-8) on the polydopamine (PDA)-modified membrane significantly raised surface energy, wettability, roughness, and stiffness of the substrate. This modulation led to an almost twofold increment in the primary attachment of dental pulp stem cells (DPSCs) compare to conventional plastic culture dishes. The findings indicate that polypropylene (PP) membrane modified by PDA/ZIF-8 coating effectively supports the growth and proliferation of DPSCs at a substantial rate. Further analysis also displayed the exaggerated multilineage differentiation of DPSCs with amplified level of autocrine cell fate determination signals, like BSP1, BMP2, PPARG, FABP4, ACAN, and COL2A. Notably, osteogenic markers were dramatically overexpressed (more than 100-folds rather than tissue culture plate) in response to biomechanical characteristics of the ZIF-8 layer.ConclusionHence, surface modification of cell culture platforms with MOF nanostructures proposed as a powerful nanomedical approach for selectively guiding stem cells for tissue regeneration. In particular, PP/PDA/ZIF-8 membrane presented ideal characteristics for using as a barrier membrane for guided bone regeneration (GBR) in periodontal tissue engineering.

Characterization of the Biomechanical and Situational Aspects of High Magnitude Subconcussive Impacts in Collegiate Football

The objective of this study was to characterize high magnitude subconcussive impacts in football to identify injurious relationships between player/game-based characteristics and impact magnitude and frequency. Subconcussive impacts are asymptomatic head impacts thought to induce alterations in the brain after repetitive exposure. Understanding factors that lead to higher magnitude or frequency of head impacts in football is crucial to develop harm reduction and prevention strategies. Eighty-one male university level football players were equipped with helmet accelerometers to capture linear acceleration (LA), impact frequency and helmet impact location. Impacts with LA = 60 g were included in the analysis. Video footage from 15 games over three seasons was analyzed to characterize aspects of play including play type, position, closing distance, player technique, tackling versus blocking and impact type (helmet-to-helmet/body/ground). A total of 570 impacts were included in the analysis with a mean LA of 83.44 g ± 23.60. Impacts with a closing distance of = 10 yards resulted in higher LA compared to <10 yards and occurred most frequently in run plays. Wide receivers and defensive backs were most often involved in impacts with a larger closing distance and experienced the highest average LA behind quarterbacks. Helmet-to-body impacts generated significantly higher LA compared to helmet-to-helmet, though helmet-to-helmet occurred more often. Players involved in a tackle sustained significantly higher LAs than those involved in a block. Impacts in which players exhibited poor technique lead to higher LA and occurred more frequently in tackling versus blocking impacts. The results of this work suggest that rules regarding offensive backfield running starts could be adjusted to decrease risk of impact after a larger closing distance. Behavioral modifications and coaching approaches aimed at improving tackling technique could decrease exposure to threshold impacts at the level of the individual player.

A Review of Psychosocial Models for the Development of Musculoskeletal Disorders and Common Psychosocial Instruments

Aims: While the biomechanical factors causing musculoskeletal disorder (MSDs) are well defined, the psychosocial dimension of MSDs is complex and affected by personal, organizational and environmental elements. There is an impetus to understand how psychosocial risk factors contribute to the manifestation of MSDs and systematically present the strengths and constraints of various instruments in assessing psychosocial risk factors.&#x0D; Study Design: This article critically reviews various models linking psychosocial constructs to MSDs and various instruments for evaluating psychosocial risk factors.&#x0D; Methodology: This article reviews the most pertinent literature which presents and discusses the connection of psychosocial domains with the development of MSDs as well as the common instruments used for evaluation of psychosocial factors.&#x0D; Results: It shows an intricate connection between psychosocial and biomechanical aspects compounded by organizational, individual and environmental factors. Psychosocial factors particularly psychological demand, decisional latitude, level of social support and work organization result in stress which produces strain and physiological deterioration hence MSDs. Different psychosocial risk factors have also been found to evoke MSDs in different body parts. Overarching cognitive and psychological aspects consisting of work demands, maneuver margins and work recognition have also been proposed in examining the psychosocial dimension of MSDs. Instruments for measuring psychological constructs are often subjective and rely on personal reflections. Some instruments assess multiple psychosocial factors while other assess specific attributes. There instruments share a common shortcoming of treating risk factors across different workplaces as homogenous.&#x0D; Conclusion: Refinement of the instruments and development of sector-specific instruments are beneficial for more reliable evaluation of psychosocial risk factors.

Crank length alters kinematics and kinetics, yet not the economy of recumbent handcyclists at constant handgrip speeds.

Handcycling performance is dependent on the physiological economy of the athlete; however, handbike configuration and the biomechanical interaction between the two are also vital. The purpose of this study was to examine the effect of crank length manipulations on physiological and biomechanical aspects of recumbent handcycling performance in highly trained recumbent handcyclists at a constant linear handgrip speed and sport-specific intensity. Nine competitive handcyclists completed a 3-minute trial in an adjustable recumbent handbike in four crank length settings (150, 160, 170 & 180mm) at 70% peak power output. Handgrip speed was controlled (1.6m·s-1 ) across trials with cadences ranging from 102 to 85rpm. Physiological economy, heart rate, and ratings of perceived exertion were monitored in all trials. Handcycling kinetics were quantified using an SRM (Schoberer Rad Messtechnik) powermeter, and upper limb kinematics were determined using a 10-camera VICON motion capture system. Physiological responses were not significantly affected by crank length. However, greater torque was generated (P<.0005) and peak torque occurred earlier during the push and pull phase (P≤.001) in longer cranks. Statistical parametric mapping revealed that the timing and orientation of shoulder flexion, shoulder abduction, and elbow extension were significantly altered in different crank lengths. Despite the biomechanical adaptations, these findings suggest that at constant handgrip speeds (and varying cadence) highly trained handcyclists may select crank lengths between 150 and 180mm without affecting their physiological performance. Until further research, factors such as anthropometrics, comfort, and self-selected cadence should be used to facilitate crank length selection in recumbent handcyclists.

Normal birth 3: Resolving Labour Dystocia Using the Principles of Biomechanics

This article focuses on the biomechanical aspect of birth, its absence from current midwifery training and how a better understanding of biomechanical processes during birth can provide a powerful tool to diagnose and resolve suboptimal positions behind dystocia. It discusses my experiences of applying simple, non-invasive techniques and fascia stretching to increase pelvic dimensions that may aid descent, flexion and rotation, resulting in a more comfortable and positive birth experience.

Selection of suitable pedicle screw for degenerated cortical and cancellous bone of human lumbar spine: A finite element study.

Pedicular arthrodesis is the traditional procedure in terms of increase in the biomechanical stability with higher fixation rate. The current work aims to identify the effect of three spinal pedicle screws considering cortical and cancellous degeneracy condition. Lumbar section L2-L3 is utilized and various load and moment conditions were applied to depict the various biomechanical parameters for selection of suitable screw. Three dimensional model is considered in finite element analysis to identify the various responses of pedicle screw at bone screw juncture. Computed tomography (CT) images of a healthy male were considered to generate the finite element vertebral model. Generated intact model was further utilized to develop the other implanted models of degenerated cortical and cancellous bone models. The three fused instrumented models with different cortical and cancellous degeneracy conditions were analyzed in finite element analysis. The results were obtained as stress pattern at bone screw boundary and intervertebral disc stress. FE simulated results represents significant changes in the von Mises stress due to various load and moment conditions on degenerated bones during different body movement conditions. Results have shown that among all pedicle screws, the 6.0 mm diameter screw reflects very less stress values at the juncture. Multiple results on biomechanical aspects obtained during the FE study can be considered to design a new stabilization device and may be helpful to plan surgery of critical sections.

Multiple roles of active stiffness in upright balance and multidirectional sway.

Both passive and active mechanisms are necessary to explain small amplitude forward-backward (FB) voluntary swaying. Parallel and symmetric leg inverted pendulum models with stiffness control are a simple way to replicate FB swaying during quiet stance. However, it has been more difficult to model lateral left-right (LR) voluntary swaying involving the dual mechanisms of hip loading-unloading and ankle pressure distribution. To assess these factors, we had subjects perform small amplitude FB and LR sways and circular rotation. We experimentally identified three parameters that characterized their two-dimensional stiffnesses: AP stiffness (KSAP), and lateral stiffness (KSML), at the ankles and a parameter we refer to as the engagement-disengagement rate (KED) of the legs. We performed simulations with our engaged leg model (Bakshi A, DiZio P, Lackner JR. J Neurophysiol 121: 2042-2060, 2019; Bakshi A, DiZio P, Lackner JR. J Neurophysiol 121: 2028-2041, 2019) to test its predictions about the limits of balance stability during sway in the three test conditions. Comparing the model's predictions with the experimental data, we found that KSAP has a task-dependent dual role in upright balance and is crucial to prevent falling; KSML helps overcome viscous drags but is not instrumental to stability; KED has a key role in stability and is dependent on the biomechanical geometry of the body, which is invariant across balance tasks. These findings provide new insights into balance control that have important clinical implications for falling, especially for patients who are unable to use a hip strategy during balance control.NEW & NOTEWORTHY Our previously published Engaged Leg Model here shows how stiffness plays complex multicausal roles in balance. In one role, it is crucial to stability, with task contingent influences over balance. In another, it overcomes viscous drag. Task-dependent stiffness alone does not explain stable balance; geometrical, invariant aspects of body biomechanics also matter. Our model is fully applicable to clinical balance pathologies involving asymmetries in movement and balance control.

Long-term effects of school barefoot running program on sprinting biomechanics in children: A case-control study

BackgroundThe acute changes of running biomechanics in habitually shod children when running barefoot have been demonstrated. However, the long-term effects of barefoot running on sprinting biomechanics in children is not well understood. Research questionHow does four years of participation in a daily school barefoot running program influence sprint biomechanics and stretch-shortening cycle jump ability in children? MethodsOne hundred and one children from barefoot education school (age, 11.2 ± 0.7 years-old) and 93 children from a control school (age, 11.1 ± 0.7 years-old) performed 50 m maximal shod and barefoot sprints and counter movement jump and five repeated-rebound jumping. To analyse sprint kinematics, a high-speed camera (240 fps) was used. In addition, foot strike patterns were evaluated by using three high-speed cameras (300 fps). Jump heights for both jump types and the contact times for the rebound jump were measured using a contact mat system. Two-way mixed ANOVA was used to examine the effect of school factor (barefoot education school vs control school) and footwear factor (barefoot vs shod) on the sprinting biomechanics. ResultsSprinting biomechanics in barefoot education school children was characterised by significantly shorter contact times (p = 0.003) and longer flight times (p = 0.005) compared to control school children regardless of footwear condition. In shod sprinting, a greater proportion of barefoot education school children sprinted with a fore-foot or mid-foot strike compared to control school children (p < 0.001). Barefoot education school children also had a significantly higher rebound jump height (p = 0.002) and shorter contact time than control school children (p = 0.001). SignificanceThe results suggest that school-based barefoot running programs may improve aspects of sprint biomechanics and develop the fast stretch-shortening cycle ability in children. In order to confirm this viewpoint, adequately powered randomised controlled trials should be conducted.

Clinical results after surgical treatment of posterolateral tibial plateau fractures ("apple bite fracture") in combination with ACL injuries.

The anterior cruciate ligament (ACL)-tear is a common injury in orthopaedic trauma. Depending on the energy of impact fractures of the posterolateral tibial plateau are often associated. Different morphologic variants of posterolateral tibial plateau impaction fractures have been described in the setting of an ACL-tear. Up to now an algorithm of treatment for a combined injury of a posterolateral tibial head fracture and an injury to the anterior cruciate ligament is missing. We present a retrospective study with clinical and radiological analysis of posterolateral fractures in combination with ACL-tear. Impressions with a depth of more than 2mm and/or a width that outreaches more than half of the posterior horn of the lateral meniscus with additional 3. degree positive pivot-shift-test indicated surgical treatment of the fracture with additional ACL repair or reconstruction. Clinical evaluation included follow-up examination, Visual Analog Scale (VAS), International Knee Documentation Committee Score (IKDC), functional and radiological Rasmussen score. 20 patients were included with a mean age of 43.6 ± 12.4 years. Mean follow-up was 18,2 ± 13,5months. The fracture was arthroscopically reduced and percutaneously fixed with a screw osteosynthesis (Group 1), reduced via a dorsal approach without (Group 2) or with an autologous bone graft (Group 3). Subjective IKDC score was 79,15 ± 6,07. Functional Rasmussen scores ranged from 27 to 30 (mean 28 ± 2.71). Radiological Rasmussen scores ranged from 16 to 18 points (mean 16.75 ± 1.33). According to IKDC score (p = 0.60), functional Rasmussen score (p = 0.829) and radiological Rasmussen score (p = 0.679) no significant discrepancy between the groups were seen. There was no failure of the ACL graft recorded. Posterolateral tibial plateau fractures in combination with an ACL-tear, can cause persistent instability and increase rotational instability. Indication for treatment of these fractures is still under debate. From the biomechanical aspect the lack of more than 50% of the posterior horn of the lateral meniscus and dislocation/depression of more than 2mm results in an increased rotational instability of the ACL deficient knee. Combined surgical treatment with ACL repair or reconstruction is a safe procedure that results in good, short-term clinical outcome, if our algorithm is followed. In addition this study shows, that majority of posterolateral tibial plateau fractures can be treated arthroscopically.

Biophysical aspects of handcycling performance in rehabilitation, daily life and recreational sports; a narrative review

Aim In this narrative review the potential and importance of handcycling are evaluated. Four conceptual models form the framework for this review; (1) the International Classification of Functioning, Disability and Health; (2) the Stress-Strain-Capacity model; (3) the Human-Activity-Assistive Technology model; and (4) the power balance model for cyclic exercise. Methods Based on international handcycle experience in (scientific) research and practice, evidence-based benefits of handcycling and optimization of handcycle settings are presented and discussed for rehabilitation, daily life and recreational sports. Results As the load can be distributed over the full 360° cycle in handcycling, peak stresses in the shoulder joint and upper body muscles reduce. Moreover, by handcycling regularly, the physical capacity can be improved. The potential of handcycling as an exercise mode for a healthy lifestyle should be recognized and advocated much more widely in rehabilitation and adapted sports practice. The interface between handcycle and its user should be optimized by choosing a suitable person-specific handcycle, but mainly by optimizing the handcycle dimensions to one’s needs and desires. These dimensions can influence efficient handcycle use and potentially improve both endurance and speed of handcycling. Conclusion To optimize performance in rehabilitation, daily life and recreational sports, continued and more systematic research is required. Implications for rehabilitation Handcycling allows users to travel farther distances at higher speeds and to train outdoors. It should be recognized as an alternative exercise modality for daily outdoor use, also already in early rehabilitation, while it contributes to a healthy lifestyle. To individualize handcycle performance, the user-handcycle (assistive device) interface as well as the vehicle mechanics should be optimized to minimize external power and reduce friction, so that the upper body capacity can be efficiently used. To optimize handcycling individual performance, both the physiological and biomechanical aspects of handcycling should be considered when monitoring or testing handcycle exercise.

Mechanical stretch sustains myofibroblast phenotype and function in microtissues through latent TGF-β1 activation.

Developing methods to study tissue mechanics and myofibroblast activation may lead to new targets for therapeutic treatments that are urgently needed for fibrotic disease. Microtissue arrays are a promising approach to conduct relatively high-throughput research into fibrosis as they recapitulate key biomechanical aspects of the disease through a relevant 3D extracellular environment. In early work, our group developed a device called the MVAS-force to stretch microtissues while enabling simultaneous assessment of their dynamic mechanical behavior. Here, we investigated TGF-β1-induced fibroblast to myofibroblast differentiation in microtissue cultures using our MVAS-force device through assessing α-SMA expression, contractility and stiffness. In doing so, we linked cell-level phenotypic changes to functional changes that characterize the clinical manifestation of fibrotic disease. As expected, TGF-β1 treatment promoted a myofibroblastic phenotype and microtissues became stiffer and possessed increased contractility. These changes were partially reversible upon TGF-β1 withdrawal under a static condition, while, in contrast, long-term cyclic stretching maintained myofibroblast activation. This pro-fibrotic effect of mechanical stretching was absent when TGF-β1 receptors were inhibited. Furthermore, stretching promoted myofibroblast differentiation when microtissues were given latent TGF-β1. Altogether, these results suggest that external mechanical stretch may activate latent TGF-β1 and, accordingly, might be a powerful stimulus for continued myofibroblast activation to progress fibrosis. Further exploration of this pathway with our approach may yield new insights into myofibroblast activation and more effective therapeutic treatments for fibrosis.