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Background and Purpose- In unilateral moyamoya disease, altered endothelial shear stress on the intact-side terminal internal carotid artery might trigger the progression to bilateral disease. We analyzed the endothelial shear stress parameters of the normally appearing terminal internal carotid artery in unilateral moyamoya disease and its association with the progression to bilateral disease. Methods- This retrospective cohort study included patients diagnosed with unilateral moyamoya disease by cerebral angiography and followed-up with regular magnetic resonance imaging/magnetic resonance angiography evaluations for >1 year. Endothelial shear stress parameters acquired were mean and maximum signal intensity gradients (SIG) and SIG SD at the vessel boundary in time-of-flight sequences in initial brain magnetic resonance imaging/magnetic resonance angiography. Contralateral disease progression defined as the detection of newly developed vessel steno-occlusion with an magnetic resonance angiography steno-occlusive stage of ≥2, in the previously intact side of the brain on follow-up magnetic resonance imaging/magnetic resonance angiography evaluation. Results- Among 146 patients (66 males [45.2%] and 80 females [54.8%]; 76 pediatric [52.1%]), contralateral disease progression was detected in 43 patients (29.5%) after a mean follow-up of 4.3±2.4 years. Multivariate analysis showed that SIG SD was significantly associated with this progression (odds ratio, 13.001 [95% CI, 1.764-95.794], P=0.012). In receiver operating characteristic curve analysis, SIG SD predicted the contralateral progression with area under the curve values of 0.803 (95% CI, 0.726-0.880, P<0.001). The regression model was reproduced in the external cohort of 31 patients. Conclusions- Increased spatial variability of the endothelial shear stress around the normally appearing terminal internal carotid artery, as measured by SIG SD in time-of-flight sequences, may predict the contralateral progression of unilateral moyamoya disease.
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Endotelio Vascular/diagnóstico por imagen , Enfermedad de Moyamoya/diagnóstico por imagen , Adolescente , Adulto , Encéfalo/diagnóstico por imagen , Arteria Carótida Interna/diagnóstico por imagen , Arteria Carótida Interna/fisiopatología , Niño , Preescolar , Estudios de Cohortes , Progresión de la Enfermedad , Endotelio Vascular/fisiopatología , Femenino , Estudios de Seguimiento , Humanos , Lactante , Angiografía por Resonancia Magnética , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Enfermedad de Moyamoya/fisiopatología , Curva ROC , Estudios Retrospectivos , Estrés Mecánico , Tomografía Computarizada de Emisión de Fotón Único , Adulto JovenRESUMEN
OBJECTIVE: To investigate the efficacy of real instrument training in virtual reality (VR) environment for improving upper-extremity and cognitive function after stroke. DESIGN: Single-blind, randomized trial. SETTING: Medical center. PARTICIPANTS: Enrolled subjects (N=31) were first-episode stroke, assessed for a period of 6 months after stroke onset; age between 20 and 85 years; patients with unilateral paralysis and a Fugl-Meyer assessment upper-extremity scale score >18. INTERVENTIONS: Both groups were trained 30 minutes per day, 3 days a week, for 6 weeks, with the experimental group performing the VR combined real instrument training and the control group performing conventional occupational therapy. MAIN OUTCOME MEASURES: Manual Muscle Test, modified Ashworth scale, Fugl-Meyer upper motor scale, hand grip, Box and Block, 9-Hole Peg Test (9-HPT), Korean Mini-Mental State Examination, and Korean-Montreal Cognitive Assessment. RESULTS: The experimental group showed greater therapeutic effects in a time-dependent manner than the control group, especially on the motor power of wrist extension, spasticity of elbow flexion and wrist extension, and Box and Block Tests. Patients in the experimental group, but not the control group, also showed significant improvements on the lateral, palmar, and tip pinch power, Box and Block, and 9-HPTs from before to immediately after training. Significantly greater improvements in the tip pinch power immediately after training and spasticity of elbow flexion 4 weeks after training completion were noted in the experimental group. CONCLUSIONS: VR combined real instrument training was effective at promoting recovery of patients' upper-extremity and cognitive function, and thus may be an innovative translational neurorehabilitation strategy after stroke.
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Rehabilitación de Accidente Cerebrovascular/métodos , Extremidad Superior/fisiopatología , Terapia de Exposición Mediante Realidad Virtual , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Masculino , Persona de Mediana Edad , Terapia Ocupacional , Recuperación de la Función , Método Simple CiegoRESUMEN
Background: Management of periprosthetic femoral fractures (PFFs) is reportedly challenging. Different patterns of PFFs would occur based on whether stem fixation was primarily cemented or cementless and whether these patterns would be associated with clinical outcomes, such as subsidence, fracture union, and complications, after stem revision. Methods: A retrospective comparative study was performed, involving 52 PFF patients treated with tapered fluted modular stems (TFMSs). In the 52 patients with Vancouver B2 or B3, including 21 cemented stems and 31 cementless stems, fracture patterns and bone stock were analyzed. Clinical outcomes after revision surgery using the TFMSs were compared between the two groups. Results: Transverse or short oblique type PFFs occurred around the cemented stem with loosening at the bone-cement interface. The Paprosky type III femoral deficiency and Vancouver type B3 fracture were observed more frequently in the cemented stem group. Otherwise, spiral fractures occurred more frequently in the cementless group (p < 0.001). Excessive subsidence of > 5 mm was observed more frequently in the cemented stem group (p < 0.001). The re-revision rates were higher in the cemented group than in the cementless group (p = 0.047). Conclusions: In our study, it was found that the patterns of transverse or oblique PFFs were more frequently produced with cemented stems, while long spiral fractures were more frequent with cementless stems. Stem subsidence and reoperation related to complications were more common in patients with PFFs around cemented stems than those with PFFs around cementless stems.
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Artroplastia de Reemplazo de Cadera , Fracturas del Fémur , Prótesis de Cadera , Fracturas Periprotésicas , Humanos , Artroplastia de Reemplazo de Cadera/efectos adversos , Artroplastia de Reemplazo de Cadera/métodos , Fracturas Periprotésicas/cirugía , Fracturas Periprotésicas/etiología , Prótesis de Cadera/efectos adversos , Estudios Retrospectivos , Diseño de Prótesis , Fracturas del Fémur/cirugía , Reoperación/métodosRESUMEN
Dysphagia is the most common complication of anterior cervical discectomy and fusion (ACDF). Several studies have reported dysphagia's incidence, severity, and prognosis after ACDF; however, few have investigated the objective effects of dysphagia management. We aimed to elucidate the efficacy of laryngeal rehabilitation therapy for dysphagia following ACDF. This prospective randomized control trial included 20 patients who underwent more than two-level ACDF. Laryngeal rehabilitation therapy was performed on 10 patients for 7 days, whereas the remaining 10 comprised the control group. Pharyngeal transit time (PTT) by videofluoroscopic swallowing study (VFSS) was performed to evaluate the objective state of swallowing. We analyzed Bazaz scale and total variance of prevertebral soft tissue swelling (PSTS) from C2 to C7 on lateral cervical radiographs during hospitalization and at 4 and 8 weeks post-surgery. The PTT of the rehabilitation group was shorter than that of the control group at 7 days and 4 weeks post-surgery (p-value; POD 7D = 0.003, POD 4W = 0.042, POD 8W = 0.097). Perioperative laryngeal rehabilitation therapy effectively reduces postoperative dysphagia after ACDF.
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OBJECTIVES: It is necessary to improve the health of older adults through exercise, but there is no concrete way to implement it or an environment in which they can exercise continuously. Our objective was to confirm the safety and efficacy of information technology (IT) convergence gamification exercise equipment for older adults. We tried to demonstrate equivalence to conventional exercise by comparing the functional improvement. DESIGN: Randomized controlled trial, with 8-week-long IT convergence exercises 3 times a week vs conventional exercise. SETTING AND PARTICIPANTS: 40 community-dwelling participants aged 60-85 years. METHOD: Participants were randomly divided into a conventional exercise group (group 1) and an IT convergence exercise group (group 2). Both groups were trained for 8 weeks, and functional assessment was performed before training (pre-evaluation), after training, and after 4 weeks of rest. RESULTS: There were functional improvements in both groups. A comparison of the differences in the functional assessment between pre-evaluation and after 8 weeks of training yielded the following results. In group 1, the mean Five Times Sit to Stand Test-30 seconds was scored as 3.60 ± 2.56 (P < .015); Five Times Sit to Stand Test-5 times, -1.75 ± 2.04 s (P < .015); Berg Balance Scale, 1.05 ± 1.39 (P < .015); Timed Up-and-Go test, -0.64 ± 0.64 s (P < .015); and 10-m Walking Test, -0.35 ± 0.47 s (P < .015). And in group 2, the mean Five Times Sit to Stand Test-30 seconds (s) was scored as 3.70 ± 2.62 (P < .015), Five Times Sit to Stand Test-5 times, -1.65 ± 1.59 s (P < .015); Berg Balance Scale, 1.05 ± 1.00 (P < .015); Timed Up-and-Go test, -0.93 ± 0.68 s (P < .015); 10-m Walking Test, -0.41 ± 0.489 s (P < .015); Chair Sit and Reach test, 2.23 ± 3.19 cm (P < .015); and Korean version of the Falls Efficacy Scale-International, -1.05 ± 1.43 (P < .015). CONCLUSION AND IMPLICATIONS: The results of this study suggest that the IT convergence gamification exercise equipment such as balpro110 has exercise effects similar to conventional exercise and also has advantages as an alternative to exercise for older adults in the next generation.
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Gamificación , Vida Independiente , Accidentes por Caídas/prevención & control , Anciano , Anciano de 80 o más Años , Ejercicio Físico , Terapia por Ejercicio/métodos , Humanos , Persona de Mediana Edad , Equilibrio PosturalRESUMEN
Whole-body vibration training (WBVT) is emerging as an alternative exercise method that be easily performed by older adults. This clinical trial investigates the efficacy of WBVT in improving muscle strength and physical performance before resistance exercise, in comparison to conventional resistance exercise after stretching exercise in older adults. The WBVT group (n = 20) performed WBVT using a vibrating platform (SW-VC15™), followed by strengthening exercises. The control group (n = 20) performed stretching instead of WBVT. Both groups underwent a total of 12 sessions (50 min per session). The primary outcome was isokinetic dynamometer. The secondary outcomes were grip strength, short physical performance battery (SPPB), a 36-Item Short Form Survey (SF-36), and body composition analysis. In all results, only the time effect was significant, and the group effect or time x group effect was not. Both groups showed a significant increase in isokinetic dynamometer. Although there was no significant group effect, the increase in mean peak torque was greater in the WBVT group. The only WBVT group showed significant improvement in SPPB. In SF-36, only the control group showed significant improvements. WBVT can be safely performed by older adults and may be an alternative exercise method to boost the effect of strengthening exercise.
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PURPOSE: Information and communication technology (ICT)-based training devices for older adults' care related to dementia are being developed to enhance older adults' cognitive functions. Older adults who require bicycle training devices can improve muscle strength and balance of lower limbs by continuously contracting and relaxing lower-limb muscles and improving cognitive function to prevent dementia. This study was conducted to investigate the effects of an ICT-based multicomponent program on body composition and cognitive function in older adults. PATIENTS AND METHODS: In a randomized controlled intervention test on 20 people over the age of 60 (exercise group: n = 10; control: n = 10), the multicomponent program was applied to the exercise group twice per week, once per day for 12 weeks, at 30 min per session, whereas the control group was advised to maintain their usual daily activities. RESULTS: Comparing body composition changes and cognitive function changes before and after intervention exhibited statistically significant differences in skeletal muscle mass (P=0.01) and modified Alzheimer's disease assessment scale-cognitive score (P=0.01) between the two groups. CONCLUSION: It can be difficult to be engaged in a simple repetitive exercise program. Therefore, to meet older adults' interests and expectations, a customized ICT-based multicomponent program, which can improve body composition and cognitive function in older adults and is believed to help prevent dementia, is recommended. TRIAL REGISTRATION: UMIN000042129 (https://www.umin.ac.jp/english/).
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Cognición/fisiología , Demencia/prevención & control , Informática Médica/métodos , Fuerza Muscular/fisiología , Terapia de Exposición Mediante Realidad Virtual/métodos , Anciano , Anciano de 80 o más Años , Ejercicio Físico/fisiología , Terapia por Ejercicio/métodos , Femenino , Humanos , Masculino , Proyectos de InvestigaciónRESUMEN
BACKGROUND: Bracing is one of the oldest non-operative treatments for patients with scoliosis. However, a wide variety of braces is used, and some show no effect, while others show conflicting results. OBJECTIVE: We aimed to evaluate the effectiveness of a new orthotic device for the treatment of adult scoliosis. METHODS: Twenty adult patients who were diagnosed with scoliosis and qualified for the study were selected and all participants were treated for 12 hours/day for 12 weeks using a new orthotic device. Various efficacy assessments (Cobb's angle, spine length, pelvic angle, shoulder angle, thoracic angle, lumbar angle, pelvic sacral angle) were performed before and after the 12-week treatment. The values at each time point were compared. RESULTS: There were significant treatment effects in a time-dependent manner on every efficacy assessment (p< 0.05) after 12 weeks of bracing. CONCLUSION: In this clinical study, it was demonstrated that a new brace that is more comfortable for the wearer reduced scoliosis and may be a useful option for non-operative treatment of scoliosis.
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Tirantes , Escoliosis/terapia , Adulto , Estatura , Femenino , Humanos , Masculino , Pelvis/patología , Escoliosis/patología , Hombro/patología , Columna Vertebral/patología , Adulto JovenRESUMEN
BACKGROUND: The amount of patients with muscle imbalance of the left and right side increases rapidly due to an incorrect lifestyle. OBJECTIVE: We investigated the optimal exercise load required to improve muscle imbalance. METHODS: Thirty participants were enrolled in the study. They performed squat exercises according to a whole body vibration (WBV) frequency protocol over a period of eight weeks. The exercises were performed three days a week and comprised five sets of fifteen trials per set per day. We validated muscle imbalance improvement using WBV by comparing and analyzing the results at different vibration frequencies. The participants were divided into three WBV protocol groups: no WBV, low-frequency WBV (25 Hz and 5 mm amplitude), and high-frequency WBV (50 Hz and 5 mm amplitude). We estimated the isokinetic muscle functions of the hip, knee, and ankle joints using BIODEX system 3. Ultimately, low-frequency WBV improved balance 10.2 â¼ 26.5% more than high-frequency WBV. RESULTS: Continuous load-deviation motions during low-frequency WBV were more effective at improving muscle imbalance than high-frequency WBV. WBV load variation methods improved muscle function and contractility more than external weights or loads by directly transferring kinetic energy into the body. CONCLUSION: In this clinical study, we demonstrated that low-frequency WBV was more effective at improving muscle imbalance. The WBV protocol can be used in rehabilitation programs to improve imbalance without requiring elderly or physically decompensated patients to participate in excessive exercise.
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Ejercicio Físico/fisiología , Extremidad Inferior/fisiología , Fuerza Muscular/fisiología , Modalidades de Fisioterapia , Vibración/uso terapéutico , Femenino , Humanos , Masculino , Adulto JovenRESUMEN
The aim of the study was to calculate the arterial wall signal intensity gradient (SIG) from time-of-flight MR angiography (TOF-MRA) and represent arterial wall shear stress. We developed a new algorithm that uses signal intensity (SI) of a TOF-MRA to directly calculate the signal intensity gradient (SIG). The results from our phantom study showed that the TOF-MRA SIG could be used to distinguish the magnitude of blood flow rate as high (mean SIG ± SD, 2.2 ± 0.4 SI/mm for 12.5 ± 2.3 L/min) and low (0.9 ± 0.3 SI/mm for 8.5 ± 2.6 L/min) in vessels (p < 0.001). Additionally, we found that the TOF-MRA SIG values were highly correlated with various flow rates (ß = 0.96, p < 0.001). Remarkably, the correlation coefficient between the WSS obtained from the computational fluid dynamics (CFD) analysis and the TOF-MRA SIG was greater than 0.8 in each section at the carotid artery (p < 0.001 for all ß values). This new technique using TOF-MRA could enable the rapid calculation of the TOF-MRA SIG and thereby the WSS. Thus, the TOF-MRA SIG can provide clinicians with an accurate and efficient screening method for making rapid decisions on the risk of vascular disease for a patient in clinical practice.
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Enfermedades Cardiovasculares/diagnóstico , Estenosis Carotídea/diagnóstico , Angiografía por Resonancia Magnética/métodos , Imagen por Resonancia Magnética/métodos , Enfermedades Cardiovasculares/diagnóstico por imagen , Enfermedades Cardiovasculares/fisiopatología , Arterias Carótidas , Arteria Carótida Común/diagnóstico por imagen , Arteria Carótida Común/fisiopatología , Estenosis Carotídea/diagnóstico por imagen , Estenosis Carotídea/fisiopatología , Medios de Contraste/uso terapéutico , Humanos , HidrodinámicaRESUMEN
The aim of this study was to investigate the effect of demineralized bone particle/ poly(lactic-co-glycolic acid) (DBP/PLGA) scaffolds on the proliferation of mesenchymal stem cells (MSCs). DBP/PLGA hybrid scaffolds were fabricated by solvent casting/salt-leaching with DBP contents of 0, 20, 40, and 80 wt%. MSCs were seeded on the DBP/PLGA scaffolds and then evaluated by a series of analytical process: SEM, MTT, RT-PCR, and in vivo histological assay. As the DBP contents increased, the cell attachment behavior and cell viability also increased. A DBP content of 80 wt% marked the best water absorption performance and the highest cell viability. Gene expression of aggrecan on DBP/PLGA scaffolds tended to increase, whereas that on PLGA scaffolds was decreased at 1 week. However, strong expression of aggrecan was observed at 2 weeks regardless of the contents of DBP. Scaffolds showed a trend of increasing type II and I collagen at 2 weeks. The results showed that MSCs on DBP/PLGA scaffolds showed more efficient cell proliferation and tissue formation in the presence of tissue-inductive stimuli. Suitable biomaterials could be more conducive to proliferation of MSCs. These results suggest that the DBP/PLGA scaffolds are a feasible biomaterial for intervertebral disc regeneration.
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Adhesión Celular , Proliferación Celular , Ácido Láctico/química , Células Madre Mesenquimatosas/fisiología , Ácido Poliglicólico/química , Andamios del Tejido , Agrecanos/metabolismo , Animales , Materiales Biocompatibles/síntesis química , Materiales Biocompatibles/química , Técnica de Desmineralización de Huesos , Bovinos , Supervivencia Celular , Células Cultivadas , Colágeno Tipo I/metabolismo , Colágeno Tipo II/metabolismo , Femenino , Expresión Génica , Humanos , Ácido Láctico/síntesis química , Ensayo de Materiales , Células Madre Mesenquimatosas/ultraestructura , Ácido Poliglicólico/síntesis química , Copolímero de Ácido Poliláctico-Ácido Poliglicólico , Ratas Wistar , Agua/químicaRESUMEN
This study investigated that the spinal MFs can create compressive follower loads (CFLs) in the lumbar spine in a dynamic state. Three-dimensional optimization and finite element (FE) models of the spinal system were developed and validated using reported experimental data. An optimization analysis was performed to determine the MFs that create CFLs in the lumbar spine in various sagittal postures from 10° extension to 40° flexion. Optimization solutions for the MFs, CFLs, and follower load path (FLP) location were feasible for all studied postures. The FE predictions demonstrated that MFs which created CFLs along the base spinal curve connecting the geometrical centers or along a curve in its vicinity (within anterior or posterior shift by 2 mm) produced stable deformation of the lumbar spine in the neutral standing and flexed postures, whereas the MFs which created the smallest CFLs resulted in unstable deformation. For extended postures, however, finding CFLs creating MFs that produce stable deformation of the extended spine was not possible. The results of this study support the hypothesis that the spinal muscles may stabilize the spine via the CFL mechanism.
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Vértebras Lumbares/fisiología , Modelos Biológicos , Contracción Muscular/fisiología , Músculo Esquelético/fisiología , Postura/fisiología , Soporte de Peso/fisiología , Articulación Cigapofisaria/fisiología , Fuerza Compresiva/fisiología , Simulación por Computador , Módulo de Elasticidad/fisiología , Estudios de Factibilidad , Humanos , Rango del Movimiento Articular/fisiología , Estrés Mecánico , Resistencia a la Tracción/fisiologíaRESUMEN
The purpose of this study was to evaluate muscle function and basal physical fitness in relation to muscle balance pattern using rowing machines. Twenty four subjects participated in this study, using three different rowing machines. Rowing exercises were performed for twenty-five times a set, four sets a day, 3 days a week, for 8 weeks. Biodex system 3(Biodex Medical Systems Co., New York, USA) was used to measure joint torques in the elbow, shoulder, lumbar and knee of subjects, for analyzing muscle function. The evaluation of basal physical fitness included body composition, muscle strength, muscle endurance, muscle reaction, agility, flexibility and explosive power. Before the experiment, significant differences of joint torques in the elbow, shoulder, lumbar and knee were present between subjects in the group. After the rowing exercise, significant improvement in every joint was witnessed. All aspects of basic fitness increased significantly, and the most improvement was observed in muscle strength from the joint torque results. As shown in the following results, every joint it was evident to have improved by more than 30% with the use of dependent load deviation type over the previously used water load method. This means that it is more effective for enhancing muscle strength and endurance to keep the muscle balance using dependent load deviation. The human body maintains motor coordination of muscle contraction during exercise. The muscle balances in the upper-lower and left-right arms could assist with effective activation of motor coordination. In this paper, an exercise method using dependent load deviation was demonstrated to be more efficient for improving muscle imbalance and strengthening muscles.
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Prueba de Esfuerzo/instrumentación , Ejercicio Físico/fisiología , Contracción Muscular/fisiología , Músculo Esquelético/fisiología , Aptitud Física/fisiología , Equilibrio Postural/fisiología , Navíos , Diseño de Equipo , Análisis de Falla de Equipo , Prueba de Esfuerzo/métodos , Femenino , Humanos , MasculinoRESUMEN
This study investigated the characteristics of dynamic postural responses when subjects attempted to maintain an upright standing position on a support plate during continuous sinusoidal perturbation in the anterior-posterior direction. Fifteen healthy young subjects participated in the experiment. Body movement patterns during the perturbation were captured and analyzed using a 3D motion analysis system (APAS 3D motion analysis, Ariel Dynamics Inc.). Seven markers were attached on the subject's body to measure and analyze the motion patterns. The markers were positioned at the head, chest, hip, right knee, left knee, right ankle, and left ankle. Five different frequencies of motion were applied to the support surface: 0.1, 0.5, 1.0, 1.5, and 2.0 Hz with a 4-cm path of motion at the base. The experiments measured dynamic postural responses in a condition were subjects had their eyes open. The results showed that the median frequency of the knee and ankle increased in all frequency bands. Following an increase in the frequency of the perturbation, the postural control strategy was changed from the ankle strategy to a combined strategy. These experimental results could be applied to the dynamic postural training for the elderly and to rehabilitation training for patients to improve their ability for postural control.
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Articulación del Tobillo/fisiología , Relojes Biológicos/fisiología , Articulación de la Cadera/fisiología , Articulación de la Rodilla/fisiología , Equilibrio Postural/fisiología , Postura/fisiología , Tiempo de Reacción/fisiología , Adulto , Retroalimentación Fisiológica/fisiología , Femenino , Humanos , Masculino , Estimulación Física/métodos , Rango del Movimiento Articular/fisiologíaRESUMEN
Knowledge about spinal loading is required for designing and preclinical testing of spinal implants. It is assumed that loading of the spine depends upon body weight and height, as well as on the spine level, but a direct measurement of the loading conditions throughout the spine is not yet possible. Here, computer models can allow an estimation of the forces and moments acting in the spine. The objective of the present study was to calculate spinal loads for different postures and activities at several levels of the thoracolumbar spine for various combinations of body height and weight. A validated musculoskeletal model, together with commercially available software (AnyBody Technology), were used to calculate the segmental loads acting on the centre of the upper endplate of the vertebrae T12 to L5. The body height was varied between 150 and 200 cm and the weight between 50 and 120 kg. The loads were determined for five standard static postures and three lifting tasks. The resultant forces and moments increased approximately linearly with increasing body weight. The body height had a nearly linear effect on the spinal loads, but in almost all loading cases, the effect on spinal loads was stronger for variation of body weight than of body height. Spinal loads generally increased from cranial to caudal. The presented data now allow the estimation of the spinal load during activities of daily living on a subject specific basis, if body height and weight are known.
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Estatura , Peso Corporal , Vértebras Lumbares/fisiología , Soporte de Peso/fisiología , Humanos , Vértebras Lumbares/anatomía & histología , Modelos Anatómicos , Postura , Reproducibilidad de los ResultadosRESUMEN
The placement of artificial disks can alter the center of rotation and kinematic pattern; therefore, forces in the spine during the motion will be affected as a result. The relationship between the location of joint center of artificial disks and forces in the spinal components is not investigated. A musculoskeletal model of the spine was developed, and three location cases of center of rotation were investigated varying 5 mm anteriorly and posteriorly from the default center. Resultant joint forces, ligament forces, facet forces, and muscle forces for each case were predicted during sagittal motion. No considerable difference was observed for joint force (maximum 14%). Anterior shift of center of rotation induced the most ligament forces (200 N) and facet forces (130 N) among the three cases. Posterior and anterior shifts of centers of rotation from the default location caused considerable changes in muscle forces, respectively: 108% and 70% of increase in multifidi muscle and 157% and 187% of increase in short segmental muscle. This study showed that the centers of rotation due to the design and the surgical placement of artificial disk can affect the kinetic results in the spine.
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Músculos de la Espalda/fisiopatología , Degeneración del Disco Intervertebral/fisiopatología , Degeneración del Disco Intervertebral/cirugía , Vértebras Lumbares/fisiopatología , Vértebras Lumbares/cirugía , Modelos Biológicos , Reeemplazo Total de Disco/instrumentación , Simulación por Computador , Humanos , Rotación , Estrés Mecánico , Reeemplazo Total de Disco/métodos , Soporte de PesoRESUMEN
A direct measurement of the complete loads in the spine continues to remain elusive. Analytical musculoskeletal models to predict the internal loading conditions generally neglect or strongly simplify passive soft tissue structures. However, during large intervertebral motions, passive structures such as ligaments and the stiffness of the intervertebral discs are thought to play a critical role on the muscle forces required for equilibrium. The objective of the present study was to add the short segmental muscles, lumbar ligaments and disc stiffnesses to an existing base musculoskeletal model of the spine in order to establish what role passive soft tissue structures play in spinal loading, but also validate these results against experimentally determined load data. The long trunk muscles not included in previous models, short segmental muscles, lumbar ligaments and disc stiffnesses were implemented into a commercially available musculoskeletal spine model construct. For several activities of daily living, the loads acting on the vertebral bodies were then calculated relative to the value for standing, and then compared to the corresponding values measured in vivo. Good agreement between calculated and measured results could be achieved in all cases, with a maximum difference of 9%. The highest muscle forces were predicted in the m. longissimus (146N) for flexion, in the m. rectus abdominis (363N) for extension, and in the m. psoas major (144N and 81N) for lateral bending and axial rotation. This study has demonstrated that the inclusion of the complete set of muscle and ligament structures into musculoskeletal models of the spine is essential before accurate spinal forces can be determined. For the first time, trend validation of spinal loading has been achieved, thus allowing confidence in the precise prediction of muscle forces for a range of activities of daily living.
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Vértebras Lumbares/anatomía & histología , Fenómenos Mecánicos , Modelos Anatómicos , Músculos/anatomía & histología , Tórax/anatomía & histología , Fenómenos Biomecánicos , Humanos , Disco Intervertebral/anatomía & histología , Disco Intervertebral/fisiología , Ligamentos/anatomía & histología , Ligamentos/fisiología , Vértebras Lumbares/fisiología , Músculos/fisiología , Presión , Reproducibilidad de los Resultados , RotaciónRESUMEN
The ligamentous spinal column buckles under compressive loads of even less than 100N. Experimental results showed that under the follower load constraint, the ligamentous lumbar spine can sustain large compressive loads without buckling, while at the same time maintaining its flexibility reasonably well. The purpose of this study was to investigate the feasibility of follower loads produced by spinal muscles in the lumbar spine in a quiet standing posture. A three-dimensional static model of the lumbar spine incorporating 232 back muscles was developed and utilized to perform the optimization analysis in order to find the muscle forces, and compressive follower loads (CFLs) along optimum follower load paths (FLPs). The effect of increasing external loads on CFLs was also investigated. An optimum solution was found which is feasible for muscle forces producing minimum CFLs along the FLP located 11 mm posterior to the curve connecting the geometrical centers of the vertebral bodies. Activation of 30 muscles was found to create CFLs with zero joint moments in all intervertebral joints. CFLs increased with increasing external loads including FLP deviations from the optimum location. Our results demonstrate that spinal muscles can create CFLs in the lumbar spine in a neutral standing posture in vivo to sustain stability. Therefore, its application in experimental and numerical studies concerning loading conditions seems to be suitable for the attainment of realistic results.