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1.
Sensors (Basel) ; 23(2)2023 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-36679405

RESUMO

Load carriage and uphill walking are conditions that either individually or in combination can compromise postural control and gait eliciting several musculoskeletal low back and lower limb injuries. The objectives of this study were to investigate postural control responses and spatiotemporal parameters of gait during level and uphill unloaded (UL), back-loaded (BL), and front-loaded (FL) walking. Postural control was assessed in 30 asymptomatic individuals by simultaneously recording (i) EMG activity of neck, thoracic and lumbar erector spinae, and rectus abdominis, (ii) projected 95% ellipse area as well as the anteroposterior and mediolateral trunk displacement, and (iii) spatiotemporal gait parameters (stride/step length and cadence). Measurements were performed during level (0%) and uphill (5, 10, and 15%) walking at a speed of 5 km h-1 without and with a suspended front pack or a backpack weighing 15% of each participant's body weight. The results of our study showed that postural control, as indicated by increased erector spinae EMG activity and changes in spatiotemporal parameters of gait that manifested with decreased stride/step length and increased cadence, is compromised particularly during level and uphill FL walking as opposed to BL or UL walking, potentially increasing the risk of musculoskeletal and fall-related injuries.


Assuntos
Marcha , Caminhada , Humanos , Suporte de Carga/fisiologia , Marcha/fisiologia , Caminhada/fisiologia , Equilíbrio Postural/fisiologia , Fenômenos Biomecânicos
2.
Sci Rep ; 13(1): 1397, 2023 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-36697465

RESUMO

Fibre-reinforced biocomposites usage has gained prominence over the past decade. Although higher fracture toughness was observed when fibres were added to biocomposites, material degradation could occur due to filler and fibre content intolerance in the biocomposite matrix. Optimisation of resin-fibre-filler ratios helps in increasing the tribological performance of high load-bearing applications. However, the tribological performance is less understood due to limited in-vitro studies on the effect of fibre microstructures. A comprehensive investigation of the reciprocating and rotary wear behaviour of different compositions was carried out by varying fibre (0%, 5%, 10% and 15%) to particulate filler (40%, 45%, 50%, and 55%) weight fractions. The investigation aimed to identify the optimal composition of fibre-reinforced biocomposites based on the in-vitro ball-on-disc reciprocating and rotary wear tests in the presence of modified Fusayama solution. The cross-sectional areas of wear tracks were analysed using laser microscopy and scanning electron microscopy techniques to assess the surface morphology and subsurface damage of the wear tracks on biocomposites and the antagonist. The numerical results were statistically analysed using two-way ANOVA followed by a posthoc Tukey's test (p = 0.05). The results showed a combination of adhesive, abrasive and fatigue wear for all the tested Groups. The friction coefficient had a longer transient period for the 5 wt% and 10 wt% Groups. Based on the surface roughness, coefficient of friction, SEMs, specific wear rate, and ease of manufacturing, the threshold limit for fibre loading was found to be 10 wt%. The rotary test had a considerably lower specific wear rate compared to the reciprocating test. Fibre weight fraction was found to be the influencing factor of the abrasive wear behaviour compared to fibre length for the tested Groups.


Assuntos
Vidro , Teste de Materiais , Fricção , Vidro/química , Suporte de Carga
3.
Sci Rep ; 13(1): 1271, 2023 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-36690640

RESUMO

Cycles of stress build-up and release are inherent to tectonically active planets. Such stress oscillations impart strain and damage, prompting mechanically loaded rocks and materials to fail. Here, we investigate, under uniaxial conditions, damage accumulation and weakening caused by time-dependent creep (at 60, 65, and 70% of the rocks' expected failure stress) and repeating stress oscillations (of ± 2.5, 5.0 or 7.5% of the creep load), simulating earthquakes at a shaking frequency of ~ 1.3 Hz in volcanic rocks. The results show that stress oscillations impart more damage than constant loads, occasionally prompting sample failure. The magnitudes of the creep stresses and stress oscillations correlate with the mechanical responses of our porphyritic andesites, implicating progressive microcracking as the cause of permanent inelastic strain. Microstructural investigation reveals longer fractures and higher fracture density in the post-experimental rock. We deconvolve the inelastic strain signal caused by creep deformation to quantify the amount of damage imparted by each individual oscillation event, showing that the magnitude of strain is generally largest with the first few oscillations; in instances where pre-existing damage and/or the oscillations' amplitude favour the coalescence of micro-cracks towards system scale failure, the strain signal recorded shows a sharp increase as the number of oscillations increases, regardless of the creep condition. We conclude that repetitive stress oscillations during earthquakes can amplify the amount of damage in otherwise mechanically loaded materials, thus accentuating their weakening, a process that may affect natural or engineered structures. We specifically discuss volcanic scenarios without wholesale failure, where stress oscillations may generate damage, which could, for example, alter pore fluid pathways, modify stress distribution and affect future vulnerability to rupture and associated hazards.


Assuntos
Fraturas Ósseas , Humanos , Estresse Mecânico , Ruptura , Suporte de Carga/fisiologia
4.
Int J Mol Sci ; 24(2)2023 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-36675050

RESUMO

Hydroxyapatite (HAP) is a calcium apatite bioceramic used in various naturally-derived and synthetic forms for bone repair and regeneration. While useful for the regrowth of osseus tissue, the poor load-bearing capacity of this material relative to other biomaterials is worsened by the propensity for pore formation during the synthetic processing of scaffolds, blocks, and granules. Here we use molecular dynamics (MD) simulations to improve the current understanding of the defect-altered uniaxial mechanical response in hexagonal HAP single crystals relative to defect-free structures. The inclusion of a central spherical pore within a repeated lattice was found to reduce both the failure stress and failure strain in uniaxial tension and compression, with up to a 30% reduction in maximum stress at the point of failure compared to a perfect crystalline structure observed when a 30 Å diameter pore was included. The Z axis ([0 0 0 1] crystalline direction) was found to be the least susceptible to pore defects in tension but the most sensitive to pore inclusion in compression. The deformation mechanisms are discussed to explain the observed mechanical responses, for which charge imbalances and geometric stress concentration factor effects caused by pore inclusion play a significant role.


Assuntos
Durapatita , Simulação de Dinâmica Molecular , Durapatita/química , Materiais Biocompatíveis/química , Apatitas , Suporte de Carga , Tecidos Suporte/química , Porosidade
5.
J Electromyogr Kinesiol ; 68: 102743, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36638696

RESUMO

Slips, trips, and falls are some of the most substantial and prevalent causes of occupational injuries and fatalities, and these events may contribute to low-back problems. We quantified lumbar kinematics (i.e., lumbar angles relative to pelvis) and kinetics during unexpected slip and trip perturbations, and during normal walking, among 12 participants (6F, 6 M). Individual anthropometry, lumbar muscle geometry, and lumbar angles, along with electromyography from 14 lumbar muscles were used as input to a 3D, dynamic, EMG-based model of the lumbar spine. Results indicated that, in comparison with values during normal walking, lumbar range of motion, lumbosacral (L5/S1) loads, and lumbar muscle activations were all significantly higher during the slip and trip events. Maximum L5/S1 compression forces exceeded 2700 N during slip and trip events, compared with âˆ¼ 1100 N during normal walking. Mean values of L5/S1 anteroposterior (930 N), and lateral (800 N) shear forces were also substantially larger than the shear force during the normal walking (230 N). These observed levels of L5/S1 reaction forces, along with high levels of bilateral lumbar muscle activities, suggest the potential for overexertion injuries and tissue damage during unexpected slip and trip events, which could contribute to low back injuries. Outcomes of this study may facilitate the identification and control of specific mechanisms involved with low back disorders consequent to slips or trips.


Assuntos
Vértebras Lombares , Músculo Esquelético , Humanos , Músculo Esquelético/fisiologia , Suporte de Carga/fisiologia , Vértebras Lombares/fisiologia , Eletromiografia , Caminhada/fisiologia , Fenômenos Biomecânicos/fisiologia
6.
J Biomech ; 147: 111439, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36638578

RESUMO

Low-back pain (LBP) continues as the leading cause of work-related musculoskeletal disorders, and the high LBP burden is attributed largely to physical risk factors prevalent in manual material handling tasks. Industrial back-support exoskeletons (BSEs) are a promising ergonomic intervention to help control/prevent exposures to such risk factors. While earlier research has demonstrated beneficial effects of BSEs in terms of reductions in superficial back muscle activity, limited evidence is available regarding the impacts of these devices on spine loads. We evaluated the effects of two passive BSEs (BackX™ AC and Laevo™ V2.5) on lumbosacral compression and shear forces during repetitive lifting using an optimization-based model. Eighteen participants (gender-balanced) completed four minutes of repetitive lifting in nine different conditions, involving symmetric and asymmetric postures when using the BSEs (along with no BSE as a control condition). Using both BSEs reduced estimated peak compression and anteroposterior shear forces (by ∼8-15%). Such reductions, however, were task-specific and depended on the BSE design. Laevo™ use reduced mediolateral shear forces during asymmetric lifting (by ∼35%). We also found that reductions in composite measures of trunk muscle activity may not correspond well with changes in spine forces when using a BSE. These results can help guide the proper selection and application of BSEs during repetitive lifting tasks. Future work is recommended to explore the viability of different biomechanical models to assess changes in spine mechanical loads when using BSEs and whether reasonable estimates would be obtained using such models.


Assuntos
Exoesqueleto Energizado , Dor Lombar , Humanos , Remoção , Coluna Vertebral/fisiologia , Vértebras Lombares/fisiologia , Região Lombossacral , Dor Lombar/prevenção & controle , Dor Lombar/etiologia , Fenômenos Biomecânicos/fisiologia , Eletromiografia , Suporte de Carga/fisiologia
7.
J Biomech ; 147: 111441, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36680886

RESUMO

Division normalization is commonly used in biomechanics studies to remove the effect of anthropometric differences (e.g., body weight) on kinetic variables, facilitating comparison across a population. In spine biomechanics, spinal forces are commonly divided by the body weight or the intervertebral load during a standing posture. However, it has been suggested that offset and power curve normalization are more appropriate than division normalization for normalizing kinetic variables such as ground reaction forces during walking and running. The present study investigated, for the first time, the effectiveness of four techniques for normalizing spinal forces to remove the effect of body weight. Spinal forces at all lumbar levels were estimated using a detailed OpenSim musculoskeletal model of the spine for 11 scaled models (50-100 kg) and during 13 trunk flexion tasks. Pearson correlations of raw and normalized forces against body weight were used to assess the effectiveness of each normalization technique. Body weight and standing division normalization could only successfully normalize L4L5 spinal forces in three tasks, and L5S1 loads in five and three tasks, respectively; however, offset and power curve normalization techniques were successful across all lumbar spine levels and all tasks. Offset normalization successfully removed the effect of body weight and maintained the influence of flexion angle on spinal forces. Thus, we recommend offset normalization to account for anthropometric differences in studies of spinal forces.


Assuntos
Vértebras Lombares , Postura , Humanos , Suporte de Carga , Fenômenos Biomecânicos , Peso Corporal
8.
J Biomech Eng ; 145(5)2023 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-36477949

RESUMO

Axial tibial rotation is a characteristic motion of the knee, but how it occurs with knee flexion is controversial. We investigated the mechanisms of tibial rotations by analyzing in vivo tibiofemoral articulations. Twenty knees of 20 living human subjects were investigated during a weightbearing flexion from full extension to maximal flexion using a dual fluoroscopic imaging system. Tibiofemoral articular contact motions on medial and lateral femoral condyles and tibial surfaces were measured at flexion intervals of 15 deg from 0 deg to 120 deg. Axial tibial rotations due to the femoral and tibial articular motions were compared. Articular contact distances were longer on femoral condyles than on tibial surfaces at all flexion intervals (p < 0.05). The articular distance on medial femoral condyle is longer than on lateral side during flexion up to 60 deg. The internal tibial rotation was 6.8 ± 4.5 deg (Mean ± SD) at the flexion interval of 0-15 deg, where 6.1 ± 2.6 deg was due to articulations on femoral condyles and 0.7 ± 5.1 deg due to articulations on tibial surfaces (p < 0.05). The axial tibial rotations due to articulations on femoral condyles are significantly larger than those on tibial surfaces until 60 deg of flexion (p < 0.05). Minimal additional axial tibial rotations were observed beyond 60 deg of flexion. The axial tibial rotations were mainly attributed to uneven articulations on medial and lateral femoral condyles. These data can provide new insights into the understanding of mechanisms of axial tibial rotations and serve as baseline knowledge for improvement of knee surgeries.


Assuntos
Articulação do Joelho , Prótese do Joelho , Humanos , Fenômenos Biomecânicos , Articulação do Joelho/fisiologia , Tíbia/fisiologia , Fêmur/fisiologia , Amplitude de Movimento Articular , Suporte de Carga/fisiologia , Rotação
9.
J Orthop Trauma ; 37(1): 38-43, 2023 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-36518065

RESUMO

OBJECTIVES: To determine whether immediate weight bearing after intramedullary fixation of extra-articular proximal tibia fractures (OTA/AO 41A) results in change of alignment before union. DESIGN: Retrospective Review. SETTING: Level I and Level II Trauma Center. PATIENTS/PARTICIPANTS: Thirty-seven patients with 37 proximal tibial fractures, all whom could bear weight as tolerated postoperatively. Eighteen fractures were OTA/AO 41-A2, and 19 were OTA/AO 41-A3. INTERVENTION: Intramedullary nailing of extra-articular proximal tibia fractures. MAIN OUTCOME MEASUREMENTS: Change in fracture alignment or loss of reduction. RESULTS: The average change in coronal alignment at the final follow-up was 1.22 ± 1.28 degrees of valgus and 1.03 ± 1.05 degrees of extension in the sagittal plane. Twenty-five patients demonstrated excellent initial alignment, 10 patients demonstrated acceptable initial alignment, and 2 patients demonstrated poor initial alignment. Five patients demonstrated a change in alignment from excellent to acceptable at the final follow-up. No patient went from excellent or acceptable initial alignment to poor final alignment. Five patients required unplanned secondary surgical procedures. Two patients required return to the operating room for soft-tissue coverage procedures, 2 patients required surgical debridement of a postoperative infection, and 1 patient underwent debridement and exchange nailing of an infected nonunion. No patient underwent revision for implant failure or loss of reduction. CONCLUSION: Immediate weight bearing after intramedullary fixation of extra-articular proximal tibia fractures (OTA/AO 41A) led to minimal change in alignment at final postoperative radiographs. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.


Assuntos
Fixação Intramedular de Fraturas , Fraturas da Tíbia , Humanos , Tíbia , Consolidação da Fratura , Resultado do Tratamento , Fixação Intramedular de Fraturas/efeitos adversos , Fixação Intramedular de Fraturas/métodos , Fraturas da Tíbia/diagnóstico por imagem , Fraturas da Tíbia/cirurgia , Suporte de Carga , Estudos Retrospectivos
10.
J Dairy Sci ; 106(2): 1065-1077, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36543638

RESUMO

Hoof overgrowth is associated with poor conformation, an altered weight-bearing surface, and a reduction in the hoof's anatomic and functional integrity. As a result of housing systems that promote hoof overgrowth, hoof trimming is considered a priority in dairy goats. However, there are few data on the effects of the timing of first trimming on hoof conformation and growth rate. The aims of this study were (1) to evaluate the long-term effects of 2 different hoof trimming start times and (2) to investigate the pattern of hoof growth across the first 2 yr of life. Eighty 5-mo-old female Saanen-cross commercially housed dairy goats were allocated randomly to 1 of 2 treatments: (1) early trimmed (trimming beginning at 5 mo old; hooves were trimmed every 4 mo thereafter) and (2) late trimmed (trimming beginning at 13 mo old; hooves were trimmed every 4 mo thereafter). Using a combination of photographs and radiographs, hoof conformation, joint positions, and hoof wall length were assessed before the 13- and 25-mo trimming events. Hoof growth was assessed every 12 wk using caliper measurements. Overall, starting hoof trimming earlier had minor and inconsistent effects. However, detrimental changes in conformation and joint positions occurred between trimming events, particularly in the hind hooves, regardless of trimming treatment. At both assessments, there was a high percentage of overgrown toes and dipped heels, with the hind hooves being more affected compared with the front (overgrown toes at 13 mo, 97.1 vs. 79.1 ± 5.2%; overgrown toes at 25 mo, 91.7 vs. 56.3 ± 6.7%; dipped heels at 13 mo, 98.5 vs. 19.3 ± 5.0%; dipped heels at 25 mo, 88.3 vs. 4.9 ± 4.8%). In addition, at both assessments, the distal interphalangeal joint angle was greater in the hind hooves compared with the front (13 mo, 79.5 vs. 65.2 ± 1.7°; 25 mo, 79.0 vs. 66.7 ± 0.9°), whereas heel angles were less in the hind hooves compared with the front (13 mo, 41.8 vs. 57.1 ± 1.5°; 25 mo, 44.9 vs. 55.9 ± 1.1°). On average, the front hooves grew 4.39 mm/mo and the hind hooves grew 4.20 mm/mo. Early trimming did not have consistent effects on hoof growth rate. Importantly, our results suggest that trimming every 4 mo is not sufficient to prevent hoof overgrowth, the development of poor conformation, and detrimental changes in joint positions, particularly in the hind hooves. Furthermore, the detrimental changes may have masked any long-term treatment effects. Therefore, trimming frequency and age of first trimming should be considered when devising hoof care protocols for dairy goats housed in environments that do not offer opportunities for natural hoof wear.


Assuntos
Doenças dos Bovinos , Doenças das Cabras , Casco e Garras , Feminino , Animais , Bovinos , Casco e Garras/cirurgia , Nova Zelândia , Suporte de Carga , Cabras
11.
J Mech Behav Biomed Mater ; 138: 105604, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36509013

RESUMO

OBJECTIVE: To evaluate the fatigue behavior of lithium disilicate crowns with a simplified anatomy against progressive cement/ceramic debonding scenarios. MATERIALS AND METHODS: Lithium disilicate crowns were fabricated via CAD/CAM and luted onto a dentin analogue material using resin cement following the manufacturer's instructions. Then, the different crown regions were isolated with paraffin oil for the absence of chemical adhesion according to four experimental groups (n = 15): Shoulder; Shoulder + Axial; Fully isolated; and Control (no insulation/fully bonded). Load to failure tests (n = 3) were run to determine cyclic fatigue parameters, and the specimens were subsequently submitted to a cyclic fatigue test (n = 12) (initial load 200 N for 5000 cycles, step 100 N, 15,000 cycles/step, frequency 20 Hz) until cracks were observed, and later fracture. The data were analyzed by Kaplan-Meier + Mantel-Cox post-hoc tests for both outcomes (cracks and fracture). Fractographic, cross-sectional surface, and finite element (FEA) analyzes were performed. RESULTS: When it comes to crack occurrence when the chemical adhesion to the occlusal surface is compromised, there is worsening (p < 0.05) in fatigue behavior compared to groups where the occlusal portion of the crown is still bonded. Considering fracture occurrence, there was no difference (p > 0.05) among the tested groups. All cracks occurred in the occlusal portion, first as a radial crack at the ceramic intaglio surface, and posteriorly unleashing a Hertzian cone crack at the top surface, resulting in fractures on the frontal walls. The interface analysis showed no interference of the insulating agent. FEA showed that as the isolated areas increased, there was also an increase in both tensile and shear stresses concentration in the crown and in the cement layer. CONCLUSION: The chemical adhesion between cement and ceramic is essential for better fatigue behavior of lithium disilicate crowns with a simplified anatomy, especially in the occlusal portion, but the restoration performance is impaired when such adhesion is compromised. There is an increase in crown and cement stress concentration with the progressive loss of chemical bonding of the crown's walls.


Assuntos
Porcelana Dentária , Cimentos de Resina , Estudos Transversais , Cerâmica , Suporte de Carga , Teste de Materiais , Análise do Estresse Dentário , Desenho Assistido por Computador , Falha de Restauração Dentária , Propriedades de Superfície
12.
J Mech Behav Biomed Mater ; 138: 105569, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36549249

RESUMO

Miniature, sharped-edge, curved-shape biomechanical elements appear in various biological systems and grant them diverse functional capabilities, such as mechanical defense, venom injection, and frictional support. While these biomechanical elements demonstrate diverse curved shapes that span from slightly curved needle-like elements (e.g., stingers), through moderately curved anchor-like elements (e.g., claws), to highly curved hook-like elements (e.g., fangs)-the curvature effect on the load-bearing capabilities of these biomechanical elements are yet mostly unknown. Here, we employ structural-mechanical modeling to explore the relationships between the curved shapes of biomechanical elements on their local deformation mechanisms, overall elastic stiffness, and reaction forces on a target surface. We found that the curvature of the biomechanical element is a prime modulator of its load-bearing characteristics that substantially affect its functional capabilities. Slightly curved elements are preferable for penetration states with optimal load-bearing capabilities parallel to their tips but possess high directional sensitivity and degraded capabilities for scratching states; contrary, highly curved elements are suitable for combined penetration-scratching states with mild directional sensitivity and optimal load-bearing capabilities in specialized angular orientation to their tips. These structural-mechanical principles are tightly linked to the intrinsic functional roles of biomechanical elements in diverse natural systems, and their synthetic realizations may promote new engineering designs of advanced biomedical injections, functional surfaces, and micromechanical devices.


Assuntos
Estresse Mecânico , Fenômenos Biomecânicos , Suporte de Carga , Fricção , Injeções
13.
Eur Radiol ; 32(3): 1429-1437, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34491384

RESUMO

OBJECTIVES: Radiographs are the most widespread imaging tool for diagnosing osteoarthritis (OA) of the knee. Our purpose was to determine which of the two factors, medial meniscus extrusion (MME) or cartilage thickness, had a greater effect on the difference in the minimum joint space width (mJSW) at the medial compartment between the extension anteroposterior view (extension view) and the 45° flexion posteroanterior view (Rosenberg view). METHODS: The subjects were 546 participants (more than 50 females and 50 males in their 30 s, 40 s, 50 s, 60 s, and 70 s) in the Kanagawa Knee Study. The mJSW at the medial compartment was measured from both the extension and the Rosenberg views, and the "mJSW difference" was defined as the mJSW in the Rosenberg view subtracted from the mJSW in the extension view. The cartilage region was automatically extracted from MRI data and constructed in three dimensions. The medial region of the femorotibial joint cartilage was divided into 18 subregions, and the cartilage thickness in each subregion was determined. The MME was also measured from MRI data. RESULTS: The mJSW difference and cartilage thickness were significantly correlated at 4 subregions, with 0.248 as the highest absolute value of the correlation coefficient. The mJSW difference and MME were also significantly correlated, with a significantly higher correlation coefficient (0.547) than for the mJSW difference and cartilage thickness. CONCLUSIONS: The MME had a greater effect than cartilage thickness on the difference between the mJSW at the medial compartment in the extension view and in the Rosenberg view. KEY POINTS: • The difference in the width at the medial compartment of the knee between the extension and the flexion radiographic views was more affected by medial meniscus extrusion than by cartilage thickness.


Assuntos
Cartilagem Articular , Osteoartrite do Joelho , Cartilagem Articular/diagnóstico por imagem , Feminino , Humanos , Articulação do Joelho/diagnóstico por imagem , Imageamento por Ressonância Magnética , Masculino , Osteoartrite do Joelho/diagnóstico por imagem , Radiografia , Suporte de Carga
14.
Spine (Phila Pa 1976) ; 47(9): E423-E431, 2022 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-34545044

RESUMO

STUDY DESIGN: Numerical in-silico human spine stability finite element analysis. OBJECTIVE: The purpose of this study was to investigate the contribution of major torso tissues toward static spine stability, mainly the thoracolumbar fascia (TLF), abdominal wall with its intra-abdominal pressure (IAP), and spinal muscles inclusive of their intramuscular pressure. SUMMARY OF BACKGROUND DATA: Given the numerous redundancies involved in the spine, current methodologies for assessing static spinal stability are limited to specific tissues and could lead to inconclusive results. A three-dimensional finite element model of the spine, with structured analysis of major torso tissues, allows for objective investigation of static spine stability. METHODS: A novel previously fully validated spine model was employed. Major torso tissues, mainly the muscles, TLF, and IAP were individually, and in combinations, activated under a 350N external spine perturbation. The stability contribution exerted by these tissues, or their ability to restore the spine to the unperturbed position, was assessed in different case-scenarios. RESULTS: Individual activations recorded significantly different stability contributions, with the highest being the TLF at 75%. Combined or synergistic activations showed an increase of up to 93% stability contribution when all tissues were simultaneously activated with a corresponding decrease in the tensile load exerted by the tissues themselves. CONCLUSION: This investigation demonstrated torso tissues exhibiting different roles toward static spine stability. The TLF appeared able to dissipate and absorb excessive loads, the muscles acted as antagonistic to external perturbations, and the IAP played a role limiting movement. Furthermore, the different combinations explored suggested an optimized engagement and coordination between different tissues to achieve a specific task, while minimizing individual work.Level of Evidence: N/A.


Assuntos
Coluna Vertebral , Tronco , Músculos Abdominais/fisiologia , Fenômenos Biomecânicos/fisiologia , Fáscia , Humanos , Músculo Esquelético/fisiologia , Coluna Vertebral/fisiologia , Tronco/fisiologia , Suporte de Carga/fisiologia
15.
Appl Ergon ; 98: 103587, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34547577

RESUMO

Anterior load carriage is common in occupational work and daily activities. Our primary purpose was to systematically review previous work concerning the biomechanics of walking with anterior load carriage. A secondary goal was to conduct a meta-analysis on common gait parameters relevant to front load carriage. An electronic database search yielded eight qualified articles. Meta-analyses were performed for four gait variables: stride length, heel contact velocity, required coefficient of friction, double support time. When possible, subgroup analyses by age were conducted. Results suggest that walking with front load carriage may shorten the stride length, particularly among young adults, but has small effects on the other three variables. Findings should be interpreted with caution given the limited number of studies included and small sample size per study. Future work investigating these four variables and others is needed to further our understanding of the impact of front load carriage on gait.


Assuntos
Marcha , Caminhada , Fenômenos Biomecânicos , Fricção , Humanos , Suporte de Carga , Adulto Jovem
16.
Georgian Med News ; (331): 54-60, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-36539131

RESUMO

The safety of early weight bearing after anterior cruciate ligament (ACL) reconstruction and the degree of posterior tibial slope (PTS) impact on ACL and ACL graft are still uncertain due to the limitations of previous studies. The study aimed to evaluate the effect of PTS change on ACL and ACL graft stress. We created the complex multicomponent static models of physiologically normal knee joint, taking into account the different PTS, the ligaments of the knee joint, including the ALL, articular cartilage, and menisci, literature data on muscle tension also with double-bundle ACL and single-bundle ACL graft to determine deformations and stress on the anatomical elements of the joint at a qualitatively new level. Stress in the knee structures was assessed using the finite element method separately with a 6 mm diameter double-bundle normal ACL and an 8 mm single-bundle ACL graft for the two variants of the tibial plateau slope: 5° and 13.9°. Raising PTS from 5° to 13.9° increases stress in the ACL by 1.29 - 1.45 times and in the single-bundle ACL graft by 1.75 - 1.81 times in the upright position with knees in full extension. Stress in ALL increases with higher PTS by 1.58-2.00 times in the knee joint with double-bundle ACL and 1.93-2.02 times in the knee joint with single-bundle ACL graft while weight bearing in full extension. Increasing the PTS angle from 5° to 13.9° with healthy ACL stress in the meniscus increases by 1.05 - 1.34 times, and with a single-bundle ACL graft - by 2.04 - 2.30 times. Replacing the double-bundle ACL with the single-bundle ACL graft also causes an increase in its stress compared to intact ACL under all studied conditions. Increased PTS and ACL reconstruction significantly increase stress in most knee anatomical elements while weight bearing in full extension. Even with a total weight of up to 150 kg, the critical value of stress for the rupture of the ACL graft from a one-time load is not achieved even after reducing its breaking load in 6 weeks. In the early postoperative period, the weakest link is the fixation of the graft with the interference screw. Cyclic load on the fully extended knee (regular walking) can provoke slipping out of the graft from under the interference screw.


Assuntos
Ligamento Cruzado Anterior , Humanos , Ligamento Cruzado Anterior/cirurgia , Articulação do Joelho/cirurgia , Tíbia/cirurgia , Suporte de Carga/fisiologia , Fenômenos Biomecânicos , Cadáver
17.
Medicina (Kaunas) ; 58(12)2022 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-36557001

RESUMO

Background and Objectives: Many people tend to carry their bags or baggage on only one side of their body. Due to smartphone use, people also tend to walk bent forward in a kyphotic posture. In this study, we aimed to assess trunk muscle activity changes due to weight-bearing, carried in the left or right hand, and using three different gait postures. Materials and Methods: We recruited 27 healthy participants (aged 19-75 years) with no history of LBP within the last 6 months before study participation. Electromyographic activities of the lower back and the abdominal muscles of the participants were evaluated using four-channel surface electromyography (EMG). Surface EMG recordings were obtained from four trunk muscles, including the flexor (rectus abdominis (RA), external oblique (EO)) and extensor muscles (lumbar erector spinae (LE), and the superficial lumbar multifidus (LM)), during unilateral weight-bearing tasks and with different gait postures (normal gait, with a sway back, and thoracic kyphosis). Results: In the "unilateral weight-bearing task", there was a significant difference in the activity of all the trunk muscles between the weight-bearing limb side and the opposite side (p < 0.05). The activation of the left trunk muscle was greater than that of the right trunk muscle when the dumbbell was lifted using the right hand. The other side showed the same result. In the "gait posture task" performed by the participants using a sway-back posture, the RA and EO had a higher level of activity in the stance and swing phases compared with that in a neutral gait (p < 0.05). Moreover, in the participants with a thoracic kyphosis posture, the LE and LM had a higher level of activity compared with that in a neutral gait (p < 0.05). Conclusions: Our results indicate that abnormal gait posture and unilateral weight-bearing tasks may impair the balance of trunk muscles, increasing the incidence of LBP. However, further large-scale, prospective, controlled studies are warranted to corroborate our results.


Assuntos
Cifose , Músculo Esquelético , Humanos , Estudos Prospectivos , Músculo Esquelético/fisiologia , Região Lombossacral , Reto do Abdome/fisiologia , Marcha , Suporte de Carga
18.
Sensors (Basel) ; 22(23)2022 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-36501877

RESUMO

Hip-worn triaxial accelerometers are widely used to assess physical activity in terms of energy expenditure. Methods for classification in terms of different types of activity of relevance to the skeleton in populations at risk of osteoporosis are not currently available. This publication aims to assess the accuracy of four machine learning models on binary (standing and walking) and tertiary (standing, walking, and jogging) classification tasks in postmenopausal women. Eighty women performed a shuttle test on an indoor track, of which thirty performed the same test on an indoor treadmill. The raw accelerometer data were pre-processed, converted into eighteen different features and then combined into nine unique feature sets. The four machine learning models were evaluated using three different validation methods. Using the leave-one-out validation method, the highest average accuracy for the binary classification model, 99.61%, was produced by a k-NN Manhattan classifier using a basic statistical feature set. For the tertiary classification model, the highest average accuracy, 94.04%, was produced by a k-NN Manhattan classifier using a feature set that included all 18 features. The methods and classifiers within this study can be applied to accelerometer data to more accurately characterize weight-bearing activity which are important to skeletal health.


Assuntos
Acelerometria , Punho , Humanos , Feminino , Acelerometria/métodos , Aprendizado de Máquina , Exercício Físico , Suporte de Carga
19.
Int J Mol Sci ; 23(23)2022 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-36499638

RESUMO

Osteoarthritis (OA) occurs not only in the knee but also in peripheral joints throughout the whole body. Previously, we have shown that the expression of cellular communication network factor 3 (CCN3), a matricellular protein, increases with age in knee articular cartilage, and the misexpression of CCN3 in cartilage induces senescence-associated secretory phenotype (SASP) factors, indicating that CCN3 promotes cartilage senescence. Here, we investigated the correlation between CCN3 expression and OA degenerative changes, principally in human femoral head cartilage. Human femoral heads obtained from patients who received total hip arthroplasty were categorized into OA and femoral neck fracture (normal) groups without significant age differences. Gene expression analysis of RNA obtained from femoral head cartilage revealed that CCN3 and MMP-13 expression in the non-weight-bearing part was significantly higher in the OA group than in the normal group, whereas the weight-bearing OA parts and normal cartilage showed no significant differences in the expression of these genes. The expression of COL10A1, however, was significantly higher in weight-bearing OA parts compared with normal weight-bearing parts, and was also higher in weight-bearing parts compared with non-weight-bearing parts in the OA group. In contrast, OA primary chondrocytes from weight-bearing parts showed higher expression of CCN3, p16, ADAMTS4, and IL-1ß than chondrocytes from the corresponding normal group, and higher ADAMTS4 and IL-1ß in the non-weight-bearing part compared with the corresponding normal group. Acan expression was significantly lower in the non-weight-bearing group in OA primary chondrocytes than in the corresponding normal chondrocytes. The expression level of CCN3 did not show significant differences between the weight-bearing part and non-weight-bearing part in both OA and normal primary chondrocytes. Immunohistochemical analysis showed accumulated CCN3 and aggrecan neoepitope staining in both the weight-bearing part and non-weight-bearing part in the OA group compared with the normal group. The CCN3 expression level in cartilage had a positive correlation with the Mankin score. X-ray analysis of cartilage-specific CCN3 overexpression mice (Tg) revealed deformation of the femoral and humeral head in the early stage, and immunohistochemical analysis showed accumulated aggrecan neoepitope staining as well as CCN3 staining and the roughening of the joint surface in Tg femoral and humeral heads. Primary chondrocytes from the Tg femoral head showed enhanced expression of Ccn3, Adamts5, p16, Il-6, and Tnfα, and decreased expression of Col2a1 and -an. These findings indicate a correlation between OA degenerative changes and the expression of CCN3, irrespective of age and mechanical loading. Furthermore, the Mankin score indicates that the expression level of Ccn3 correlates with the progression of OA.


Assuntos
Cartilagem Articular , Osteoartrite , Animais , Humanos , Camundongos , Agrecanas/metabolismo , Cartilagem Articular/metabolismo , Condrócitos/metabolismo , Articulação do Quadril/metabolismo , Osteoartrite/metabolismo , Suporte de Carga
20.
Braz. j. oral sci ; 21: e226999, jan.-dez. 2022. ilus
Artigo em Inglês | LILACS, BBO - Odontologia | ID: biblio-1392965

RESUMO

Background: Tooth extraction socket in the aesthetic area is a major indication for immediate implant placement greatly improving patient satisfaction and preserving the alveolar ridge. However, the effect of non-axial force on the peri-implant bone with subsequent early implant failure remains unclear. Objective:Evaluate the prognosis of tilted implants immediately placed and restored with angled abutments in comparison to straight implants restored with straight abutments in the esthetic area (anterior or premolars) using computer-aided surgical guides. Material and methods: Badly decayed non-restorable teeth in the aesthetic zone (anterior or premolars) were extracted atraumatically. Immediately after guided implant insertion, the abutments were adjusted and placed according to the allocation group (0, 15, or 25-degree angle) then a temporary crown was performed out of occlusion in centric and eccentric relation. Early implant failure was assessed at three and six months. Results:There was no statistically significant difference between the two groups (P=0.305). Straight and angled abutment groups showed 6 (14.3%) and 8 (20%) failed cases, respectively. The post-hoc subgroup analysis showed no statistically significant difference between angle 15 and angle 25 degree groups where (P=0.686) or between Anterior and Premolar groups (P=0.853). Conclusion: There was no statistically significant difference in the failure rate when comparing angled to straight immediately placed & restored implants. This applies to both anterior and premolar implants


Assuntos
Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Prognóstico , Extração Dentária , Suporte de Carga , Falha de Restauração Dentária , Implantação Dentária , Carga Imediata em Implante Dentário
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