Three Dimensional Ultrasound Analysis of Fascicle Orientation in Human Tibialis Anterior Muscle Enables Analysis of Macroscopic Torque at the Cellular Level
The purpose of this study was to test the hypothesis that the internal structure of the bipennate human tibialis anterior muscle is sufficiently homogenous throughout the muscle that the cellular stresses could be interpreted correctly from measurable anatomic properties and torque in the limb. This result is needed for facile comparison of extrinsic mechanical data and intrinsic energetic fluxes. Three-dimensional imaging of the fascicles of the human tibialis anterior muscle was made by capturing a series of ultrasound images while registering their location in space. Subsequent tracing of hundreds of structures in the ultrasound images with the use of custom software identified muscle boundaries, tendon surfaces, and fascicles as anatomic elements in 3-D space. The tendon was reconstructed as a mesh through the tracings identified as a component of the tendon. The angle of insertion of each identified fascicle at the tendon was calculated against the nearest normal in the mesh of the tendon. In three subjects the average angle of insertion of the fascicles onto the internal tendon was 11° (coefficient of variation 40%). The angle decreased along the length of the muscle from ∼ 15° near the belly of the muscle to 6° near the ankle in fascicles superior and inferior to the central tendon. The angle increased by several degrees during a voluntary contraction. Despite the differences in angles of insertion that can be measured, these distinctions have little significance for the distribution of forces along cellular axes within the muscle: the angles, their distribution within the muscle and change with contraction are small. For his bipennate muscle the cosine of the angle of insertion of the cellular bundles is always close to unity. Thus measurements of whole muscle mechanical data are simply related to mechanical stress of its cells.
KeywordsMaximal Voluntary Contraction Human Muscle Tibialis Anterior Muscle Maximal Voluntary Isometric Contraction Muscle Fascicle
Unable to display preview. Download preview PDF.
- Narici, M. V., T. Binzoni, et al. (1994). “Human gastrocnemius muscle architecture from rest to the contracted state.” Journal of Physiology 475: 17 P.Google Scholar
- Sheehan, F. H., E. L. Bolson, et al. (1998). “Three Dimensional Echocardiography System for Quantitative Analysis of the Left Ventricle.” IEEE Computers in Cardiology 25: 649–652.Google Scholar
- Spoor, C. W., J. L. Van Leeuwen, et al. (1991). “Active Force-Length Relationship of Human Lower-leg 29(3): Muscles Estimated from Morphological Data: a Comparison of Geometric Muscle Models.” Europ. J. Van Morphol. 137–160.Google Scholar
- Leeuwen, J. L. and C. W. Spoor (1996). “A Two Dimensional Model for the Prediction of Muscle Shape and. Intramuscular Pressure.” Europ. J. Morphol. 34(1): 15–30.Google Scholar