RESUMEN
The study examined the sensitivity of two musculoskeletal models to the parameters describing each model. Two different models were examined: a phenomenological model of human jumping with parameters based on live subject data, and the second a model of the First Dorsal Interosseous with parameters based on cadaveric measurements. Both models were sensitive to the model parameters, with the use of mean group data not producing model outputs reflective of either the performance of any group member or the mean group performance. These results highlight the value of subject specific model parameters, and the problems associated with model validation.
Asunto(s)
Modelos Biológicos , Adulto , Antropometría , Fenómenos Biomecánicos , Cadáver , Simulación por Computador , Humanos , Rodilla/fisiología , Locomoción , Masculino , Músculo Esquelético/fisiología , Reproducibilidad de los ResultadosRESUMEN
The quantification in vivo of muscle volume is important, for example, to understand how muscles change with aging, and respond to rehabilitation. Albracht et al. (2008) suggested that muscle volume can be estimated in vivo from the measurement of muscle cross-sectional area and muscle belly length only. The purpose of this study was to evaluate this proposed relationship for determining muscle volume for both the Vastus Lateralis (VL) and First Dorsal Interosseous (FDI) using ultrasound imaging. The cross-sectional area and length of 22 cadaver FDI and 6 VL muscles in cadavers were imaged using ultrasound, these muscles were then dissected and muscle volumes measured directly using the water displacement technique. Estimated muscle volumes were compared with their direct measurement, and for the VL the percentage root mean square error in the estimation of muscle volume was 5.0%, and the Bland-Altman analysis had all volume estimates within the 95% confidence interval, with no evidence of bias (proportional or constant) in the volume estimates. In contrast, percentage root mean square error for the FDI was 18.8%, with the Bland-Altman analysis showing volume estimates outside of the 95% confidence interval and proportional bias. These results indicate that the simple method proposed by Albracht et al. (2008) for the estimation of muscle volume is appropriate the VL but not the FDI using ultrasound imaging. Morphological disparities likely account for these differences, if accurate and fast measures of the volume of the FDI are required other approaches should be explored.
Asunto(s)
Músculo Esquelético/anatomía & histología , Anciano , Anciano de 80 o más Años , Cadáver , Mano , Humanos , Pierna , Persona de Mediana Edad , Músculo Esquelético/diagnóstico por imagen , UltrasonografíaRESUMEN
The pennated arrangement of muscle fibers has important implications for muscle function in vivo, but complex arrangement of muscle fascicles in whole muscle raises the question whether the arrangement of fascicles produce variations in pennation angle throughout muscle. The purpose of this study was to describe the variability in pennation angle observed throughout the first dorsal interosseous (FDI) muscle using magnetic resonance imaging (MRI). Two cadaveric muscles were scanned in a 14.1 tesla MRI unit. Muscles were divided into slices and pennation angle was measured in the same representative location throughout the muscle in each slice for the medial-lateral and anterior posterior-image planes. Data showed large nonuniform variation in pennation angles throughout the muscles. For example, for cadaver 2, pennation angle in 287 planes along the medial-lateral axis ranged from 3.2° to 22.6°, while for the anterior-posterior axis, in 237 planes it ranged from 3.1° to 24.5°. The nonnormal distribution of pennation angles along each axis suggests a more complex distribution of fascicles than is assumed when a single pennation angle is used to represent an entire muscle. This distribution indicates that a single pennation angle may not accurately describe the arrangement of muscle fascicles in whole muscle.
Asunto(s)
Mano/anatomía & histología , Imagen por Resonancia Magnética , Fibras Musculares Esqueléticas/ultraestructura , Músculo Esquelético/anatomía & histología , Cadáver , Humanos , Técnicas In VitroRESUMEN
Subject specific musculoskeletal models typically base some or all of their parameters on a source other than the subject being modeled. Evidence demonstrates that cadaveric measurements do not always scale appropriately to every subject, yet many musculoskeletal models still rely heavily on cadaveric based data. This study focused on the First Dorsal interosseous (FDI) given its unique function as the sole abductor of the second metacarpophalangeal joint. There were two purposes to this study: (1) to describe the procedures that can be used in vivo to determine the properties of a model of the FDI. (2). To determine the model parameters required to characterize the FDI for a group of four subjects. Parameters were determined using ultrasound imaging and a custom-built finger dynamometer. Some parameters were measured directly while other parameters had to be estimated using a least-squares criterion. For example, the parameters for the force-length properties were determined by fitting a model to experimentally determined data, with maximum isometric force values ranging from 86 to 102 N, and optimum lengths from 41 to 53 mm. It was shown that full characterization is possible for the FDI with parameters that are physiologically reasonable, but which showed variability between subjects. This model and approach for parameter identification will allow for more detailed analysis of the function of the FDI.
Asunto(s)
Dedos/fisiopatología , Contracción Isométrica/fisiología , Modelos Biológicos , Dinamómetro de Fuerza Muscular , Fuerza Muscular/fisiología , Músculo Esquelético/fisiología , Adulto , Humanos , MasculinoRESUMEN
The architecture of the muscle fascicles, here meaning their lengths and their arrangement relative to one another, has important implications for the force a muscle can produce. Therefore, quantifying this architectural arrangement and understanding the implications of the architecture are important for understanding muscle function in vivo. There were two purposes of this study: (1) to assess, via blunt dissection, the number and the length of all the fascicles comprising the First Dorsal Interosseous (FDI) muscle and (2) to visually identify, via magnetic resonance imaging (MRI), the arrangement of the fascicles comprising the FDI. Simple blunt dissection of all the fascicles comprising four FDI muscles and their subsequent measurement demonstrated that the fascicles comprising the whole muscle were not as long as the muscle belly from which they were extracted. Muscle fascicles are surrounded by connective tissue hence the paths of the fascicles in two whole FDI muscles were identified via MRI by tracking the connective tissue surrounding the fascicles. The fascicles had a spiral pattern along the length of each muscle, within both muscles many of the fascicles were arranged in series with other fascicles. These architectural features of the fascicles of the FDI have important implications for the force-length and force-velocity properties of the whole muscle.
Asunto(s)
Fascículo Atrioventricular/anatomía & histología , Tejido Conectivo/anatomía & histología , Músculos/anatomía & histología , Músculos/fisiología , Anciano , Anciano de 80 o más Años , Fenómenos Biomecánicos , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana EdadRESUMEN
Accurate in vivo estimation of muscle volume is important as it indicates the amount of power a muscle can produce. By tracking muscle volume changes in vivo, a muscle's response to disease or rehabilitation training can be quantified. The purpose of this study was to validate the use of imaging ultrasound to estimate the volume of a small muscle, specifically the First Dorsal Interosseous (FDI) muscle. The perimeter of the FDI was imaged using ultrasound in 22 cadaver hands. For each FDI, serial cross-sectional areas were determined by manual digitization, volumes were then estimated using the Cavalieri principle. The muscles were then dissected from the cadavers, and muscle volume was determined via the water displacement method. The water displacement measures of muscle volumes were used as the criterion, and compared with those estimated via ultrasound. A Bland-Altman plot illustrated that all measures fell within the 95% confidence interval, with no statistical evidence of changes in measurement accuracy with size of specimen, or of a constant deviation in the accuracy of estimated volumes. For superficial muscles these results indicate that ultrasound imaging is an accurate method for determining muscle volumes in vivo even for a relatively small muscle (volume â¼4 mL).
Asunto(s)
Mano/diagnóstico por imagen , Músculo Esquelético/anatomía & histología , Músculo Esquelético/diagnóstico por imagen , Humanos , Persona de Mediana Edad , Variaciones Dependientes del Observador , Tamaño de los Órganos , UltrasonografíaRESUMEN
Estimation of muscle fiber optimum length is typically accomplished using either laser diffraction or by counting the number of sarcomeres in a portion of the muscle fiber, measuring the distance that encompasses those sarcomeres and dividing by the number of sarcomeres to obtain an average sarcomere length. If the sarcomeres are not uniformly distributed, either of these techniques could produce errors when estimating optimum lengths. The purposes of this study were: to describe new software that automatically analyzes digital images of skeletal muscle fibers to measure individual sarcomere lengths; and to use this software to measure individual sarcomere lengths along complete muscle fibers to examine the influence of computing whole muscle fiber properties from portions of the fiber. Six complete muscle fibers were imaged using a digital camera attached to a microscope. The images were then processed to achieve the best resolution possible, individual sarcomeres along the image were detected, and each individual sarcomere length was measured. The software accuracy was compared with that of manual measurement and was found to be as accurate. In addition, the time to measure individual sarcomere lengths was greatly reduced using the software compared with manual measurement. The arrangement of individual sarcomere lengths demonstrated long-range correlations, which indicates problems in assuming only a portion of a fiber can be used to determine whole fiber properties. This study has provided evidence on the number of sarcomeres which must be analyzed to infer the properties of whole muscles.
Asunto(s)
Procesamiento de Imagen Asistido por Computador/métodos , Fibras Musculares Esqueléticas/citología , Músculo Esquelético/anatomía & histología , Sarcómeros/ultraestructura , Cadáver , Humanos , Fibras Musculares Esqueléticas/ultraestructura , Músculo Esquelético/citología , Músculo Esquelético/ultraestructura , Programas InformáticosRESUMEN
Muscle architecture is considered to reflect the function of muscle in vivo, and is important for example to clinicians in designing tendon-transfer and tendon-lengthening surgeries. The purpose of this study was to quantify the architectural properties of the FDI muscle. It is hypothesized that there will be consistency, that is low variability, in the architectural parameters used to describe the first dorsal interosseous muscle because of its clear functional role in index finger motion. The important architectural parameters identified were those required to characterize a muscle adequately by modeling. Specifically the mass, cross-sectional area, and length of the tendon and muscle were measured in cadavers along with the muscle fiber optimum length and pennation angle, and the moment arm of the first dorsal interosseous at the metacarpophalangeal joint. These parameters provide a characterization of the architecture of the first dorsal interosseous, and were used to indicate the inherent variability between samples. The results demonstrated a large amount of variability for all architectural parameters measured; leading to a rejection of the hypothesis. Ratios designed to describe the functioning of the muscles in vivo, for example the ratio of tendon to fiber optimum lengths, also demonstrated a large variability. The results suggest that function cannot be deduced from form for the first dorsal interosseous, and that subject-specific architectural parameters may be necessary for the formulation of accurate musculoskeletal models or making clinical decisions.
Asunto(s)
Mano/fisiología , Contracción Muscular/fisiología , Músculo Esquelético/fisiología , Tendones/fisiología , Adulto , Anciano , Anciano de 80 o más Años , Fenómenos Biomecánicos , Cadáver , Femenino , Mano/anatomía & histología , Humanos , Masculino , Modelos Biológicos , Músculo Esquelético/anatomía & histología , Tendones/anatomía & histologíaRESUMEN
The purpose of this study was to validate ultrasound muscle volume estimation in vivo. To examine validity, vastus lateralis ultrasound images were collected from cadavers before muscle dissection; after dissection, the volumes were determined by hydrostatic weighing. Seven thighs from cadaver specimens were scanned using a 7.5-MHz ultrasound probe (SSD-1000, Aloka, Japan). The perimeter of the vastus lateralis was identified in the ultrasound images and manually digitized. Volumes were then estimated using the Cavalieri principle, by measuring the image areas of sets of parallel two-dimensional slices through the muscles. The muscles were then dissected from the cadavers, and muscle volume was determined via hydrostatic weighing. There was no statistically significant difference between the ultrasound estimation of muscle volume and that estimated using hydrostatic weighing (p > 0.05). The mean percentage error between the two volume estimates was 0.4% +/- 6.9. Three operators all performed four digitizations of all images from one randomly selected muscle; there was no statistical difference between operators or trials and the intraclass correlation was high (>0.8). The results of this study indicate that ultrasound is an accurate method for estimating muscle volumes in vivo.