Abstract To address the current problems of low accuracy and poor reliability of the discrete element model of cotton stalks, as well as the difficulty of guiding the design and optimization of the ...equipment through simulations, the discrete element modeling and physical-mechanical tests of cotton stalks in machine harvested film-stalk mixtures are carried out. The peak tensile force $$F_{\rm j}^{\max }$$ F j max , the peak pressure $$F_{\rm y}^{\max }$$ F y max , the peak bending force $$F_{\rm w}^{\max }$$ F w max , the peak shear force $$F_{\rm j}^{\max }$$ F j max , and the force-displacement ( F – x ) curves of cotton stalks are obtained from the physical tests. The discrete element model of double-layer cotton stalks based on the flat-joint model is established with the PFC $$^{\rm 3D}$$ 3 D software. The $$F_{\rm y}^{\max }$$ F y max is taken as the response value, and the microscopic parameters of the cotton stalk model are used as the test factors, then the Plackett–Burman test, the steepest climb test, and the Box–Behnken test are sequentially designed using Design-Expert software. The second-order regression model describing the relationship between the $$F_{\rm y}^{\max }$$ F y max and the microscopic parameters is established. The optimal parameter combinations of the microscopic parameters are obtained, and then they are utilized to construct the compression, bending, and shear models of cotton stalks and to carry out the validation tests. The results confirm that the established discrete element model could accurately characterize the biomechanical properties of cotton stalks and that the parameter calibration method is reasonable, which could provide a reference for the discrete element modeling of cotton stalks and other stalks, and also offer a theoretical basis for the research of the crushing and separation mechanism of the film-stalk mixtures and the development of the equipment.
The potential of biomechanics for improving human health and performance is well established in many parts of the world. However, across most of Africa, biomechanics remains relatively ...underdeveloped. The discussion around biomechanics in the continent has increased in recent times and young African scientists are pursuing career opportunities in biomechanics-related fields within Africa and in other parts of the world. New institutions and programmes that focus on biomechanics teaching and research are also starting up around the continent. The advent of the National Biomechanics Day event, formation of the first formal biomechanics society in South Africa, along with many collaborations with relevant stakeholder organizations around the world underpin the expansion of biomechanics in Africa. This article aims to summarize the current state and describe aspirations for the future of biomechanics in Africa.
Abstract Aim Abdominal wall hernias result from a mechanical conflict between forces acting on the wall (mainly intra-abdominal pressure (IAP)) and its ability to deform. An abdominal binder ...instrumented with sensors has been developed to non-invasively quantify the deformation during straining. Methods A prospective study was conducted on eight healthy subjects. External deformations were evaluated by a patented connected binder instrumented with resistive sensors covering anterolateral area. IAP was evaluated by intragastric ingested sensor (SmartPill™, Medtronic), and wall muscles deformation by dynamic MRI (semi-automated segmentation method applied to rectus abdominis (RA) and lateral muscle (LM)). The relationship between these signals has been investigated during Valsalva maneuver. Results The binder provided time-related mapping of the abdominal deformation. Two different patterns were individualized corresponding to RA and LM areas. Deformation rate (mean 1.21mV/s for RA and 1.66mV/s for LM) and maximum signal (mean 3.03mV for RA and 4.24mV for LM) were recorded. These binder patterns were both correlated with the deep deformation in abdominal muscles observed in MRI (Pearson R=0.89 for RA, and R=0.94 for LM; p<0.005). The binder patterns were also significantly correlated with the IAP variation (Pearson R=0.98 for RA and R=0.99 for LM; p<0.005). Conclusion This non-invasive connected and instrumented abdominal binder simply and quickly reflects the abdominal wall muscles deformation and IAP variation during Valsalva maneuver. A larger study is needed to investigate inter-individual variability, and to evaluate the links between quantitative mechanical behavior and surgical outcomes during hernia surgery.
Introduction:Osteoarthritis (OA) is a prevalent degenerative joint disease, especially in the elderly, posing a significant public health concern. Hip osteoarthritis affects millions of individuals ...worldwide and significantly impairs their quality of life. Surgical interventions for hip osteoarthritis aim to alleviate pain and restore function. Surgeons face a choice of surgical approaches, including anterior, posterior, and lateral approaches, each with its advantages and risks. This narrative review explores the consequences of these approaches on patients' functional and motor capacities, with a hypothesis that the anterior approach may offer superior functional recovery due to better muscle and tissue preservation.Methods:The review was conducted by searching PubMed and ScienceDirect for articles published between 2010 and 2023, written in English, and related to primary hip arthroplasty. The search focused on keywords related to hip arthroplasty, gait, locomotion, functional recovery, and surgical approach. A total of 98 potentially relevant articles were identified, and 72 met the inclusion criteria. Various questionnaires were used to assess the outcomes, such as HOOS, OHS, and SF-36.Results and Discussion:The review included 30 articles comparing the effects of anterior vs. posterior approach, 11 comparing anterior vs. lateral approach, and 1 comparing lateral vs. posterior approach. Eight articles studied all three approaches. The posterior approach offers better visibility of the hip joint but may result in more post-operative pain and a higher risk of hip dislocation due to muscle weakness. The lateral approach provides direct visibility of the hip joint and faster recovery but can also lead to postoperative pain and abductor weakness. The anterior approach, while requiring more surgical expertise, offers advantages such as reduced hospital stay, decreased pain, lower risk of dislocation, and faster recovery, including improved gait and hip flexion.Some articles noted a significant temporal effect for maximum hip extension and stride length, with the anterior approach showing better results in the short term. However, differences tend to disappear beyond three months post-surgery, especially with the lateral approach.Conclusions:Most studies suggest that the direct anterior approach may result in greater early postoperative improvements compared to lateral and posterior approaches. The choice of approach should depend on the surgeon's experience and the patient's specific needs. All three approaches have their pros and cons, but they yield similar results one year after surgery. Patients should engage in discussions with their surgeons and ask relevant questions to make informed decisions. Future research should focus on assessing rehabilitation efficiency based on the surgical approach chosen.
Industry 4.0 is the implementation of intelligent technologies to increase productivity and reduce the associated biomechanical risks 1. From a general perspective, the integration of ergonomics and ...human factors requirements in human-robot collaborative (HRC) systems, such as collaborative robots (CoBots), represents a new option to reduce the physical effort of workers during the performance of manual material handling (MMH) activities and to introduce new ergonomic interventions for the prevention of work-related musculoskeletal disorders (WMDs). As the use of CoBots in manufacturing has recently increased significantly, all potential benefits need to be thoroughly investigated and proven, especially in the MMH activities where the physical interaction of the worker with the CoBot takes place. While the safety in this new hybrid scenario is widely studied, the effects on workers' health are still limited 2. The present study aims to investigate the biomechanical parameters of workers performing an industrial use case with (wB) and without (woB) a dual-arm CoBot.
Purpose of Review
Fractures of osteoporotic bone in elderly individuals need special attention. This manuscript reviews the current strategies to provide sufficient fracture fixation stability with a ...particular focus on fractures that frequently occur in elderly individuals with osteoporosis and require full load-bearing capacity, i.e., pelvis, hip, ankle, and peri-implant fractures.
Recent Findings
Elderly individuals benefit immensely from immediate mobilization after fracture and thus require stable fracture fixation that allows immediate post-operative weight-bearing. However, osteoporotic bone has decreased holding capacity for metallic implants and is thus associated with a considerable fracture fixation failure rate both short term and long term. Modern implant technologies with dedicated modifications provide sufficient mechanical stability to allow immediate weight-bearing for elderly individuals. Depending on fracture location and fracture severity, various options are available to reinforce or augment standard fracture fixation systems.
Summary
Correct application of the basic principles of fracture fixation and the use of modern implant technologies enables mechanically stable fracture fixation that allows early weight-bearing and results in timely fracture healing even in patients with osteoporosis.
Category:
Midfoot/Forefoot; Sports
Introduction/Purpose:
The preferred method of fixation for ligamentous Lisfranc injuries is controversial, with the traditional method being transarticular screws. ...Unfortunately, screw removal is often required leading surgeons to seek alternative fixation methods including fibertape constructs. The purpose of this biomechanical study is to compare transarticular screws to a fibertape construct under a spectrum of biomechanical loads. This controlled laboratory study involved evaluating the diastasis at three joints in the Lisfranc complex in matched pairs and creating 3D models for each loading stage to evaluate at the plantar, interosseous, and dorsal aspects of each bone.
Methods:
Eight matched pairs of lower extremity cadaveric specimens were fixed with either a fibertape construct with a supplemental intercuneiform limb, or two transarticular cannulated crossed-screws. The diastasis between bones was measured at three midfoot joints in the Lisfranc complex; the Lisfranc articulation, the 2nd tarsometatarsal joint, and the intercuneiform joint using a 3D coordinate digitizer. Measurements were obtained for the pre-injured, injured, and fixation under static loading at 50% donor bodyweight. Specimens then underwent stepwise increases in cyclic loading performed at 1 Hz and 100 cycles, at additional 100 N ground reaction force intervals from 100 N to 2000 N to simulate postoperative loading from the partial weightbearing stage to high-energy activities. CT scans were obtained for each specimen to create 3D models that allowed for plantar and interosseous diastasis measurements. Failure of fixation was defined as diastasis greater than 2 millimeters at the Lisfranc articulation (second-metatarsal - medial-cuneiform joint).
Results:
There were no significant differences detected between groups in the pre-injury, injury or fixation stage and therefore no notable differences between groups prior to surgery with different constructs. Specimens fixed with the fibertape construct demonstrated failure in 1 of 8 (12.5%) specimens during a cycle with a peak force of 2000 N. In contrast, 2 of 8 (25%) specimens fixed with screws failed at peak forces of 1000 N and 1400 N. There were no significant differences in diastasis detected at the Lisfranc articulation or the intercuneiform joint throughout all loading cycles. However, the fibertape construct showed higher non-failure in statistical predictions, and significantly less motion at the adjacent 2nd tarsometatarsal joint.
Conclusion:
This study displayed a high level of repeatability in our injury creation under fluoroscopy with a specific criteria to avoid disrupting any adjacent ligaments and a threshold measurement of injury. The fibertape construct with a supplemental intercuneiform limb seems to provide comparable biomechanical stability to transarticular screws. There were no significant differences detected throughout our loading protocol which exceeds loads performed in previous studies. Furthermore, in combination with not requiring removal, this construct may allow for physiologic loading potentially providing accelerated post- operative protocols.
Scapholunate ligaments (SLLs) play a well-established role in maintaining carpal alignment and kinematics, and are innervated with sensory mechanoreceptors located within the ligaments. They are ...involved in the afferent arc of dynamic wrist stability. The aim of this study was to describe the changes in these mechanoreceptor populations in injured SLLs.
Injured SLLs were collected from human wrists at the time of SLL reconstruction or limited wrist fusion, where the ligament remnants would otherwise be discarded. These specimens were formalin-fixed and paraffin-embedded for immunohistochemical analysis to identify mechanoreceptors, which were then classified by type and location within the ligament.
A total of 15 ligaments were collected, with the interval from injury ranging from 39 days-20 years. Eleven ligaments were collected less than one year after injury, and four ligaments were collected two years or more after injury. A total of 66 mechanoreceptors were identified, with 50 mechanoreceptors identified in nine of the 11 specimens collected less than one year after injury. In this group, 54% of the mechanoreceptors resided in the volar subunit, 20% in the dorsal subunit, and 26% in the proximal subunit. Two of the four specimens collected two years or later after injury contained mechanoreceptors, all of which were located in the dorsal subunit. Increasing time from injury demonstrated a decline in mechanoreceptor numbers within the volar subunit.
Mechanoreceptors were consistently located in the SLL, particularly in the volar subunit of specimens collected less than one year after injury.
Ligament reconstruction techniques aim to primarily reconstitute the biomechanical function of the disrupted SLL; however, re-establishing the afferent proprioceptive capacity of the SLL may be a secondary objective. This suggests the need to consider the reconstruction of its volar subunit particularly in those managed within one year of injury.
Optimal postural stability is required to perform in archery. Since the dynamic consequences of the string release may disturb the archer's postural equilibrium, they should have integrated them in ...their motor program to optimize postural stability. This study aimed to characterize the postural strategy archers use to limit the potentially detrimental impact of the bow release on their postural stability and identify characteristics that may explain a better performance. Six elite and seven sub-elite archers performed a series of 18 shots at 70 meters, standing on two force plates. Postural stability indicators were computed during the aiming and the shooting phase using the trajectory of the center of pressure. Two postural strategies were defined, as whether they were triggered before (early) or after (late) the string release time. Both groups used anticipated postural adjustments, but elite archers triggered them before the string release more often and sooner. Scores differed between the two groups, but no differences were found between early and late shots. Trained archers seem to have finely integrated the dynamic consequences of their bow motion, triggering anticipated postural adjustments prior to the string release. However, it remains unclear whether this anticipation can positively influence the performance outcome.
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