Musculoskeletal geometry

The nervous system can learn to achieve desired levels of accuracy by adjusting control signals to accommodate factors such as changing musculoskeletal geometry, and dynamics. For example, when an object is grasped and lifted with fingers, the grip force varies directly in an anticipation of the load force as determined by mass and acceleration of the object [ 13-16]. 

If the musculoskeletal geometry is included, muscle forces can then be estimated firom the joint moments, and from these it may be possible to estimate ligament and joint compressive forces. 

The musculoskeletal model requires the muscle force simulation and the musculoskeletal geometry. For the muscle force simulation, Hill-based muscle models have been used for... 

The musculoskeletal geometry is required for the calculation of the muscle length. The musculoskeletal geometry consists of the three dimensional location of muscle attachment and the position relation of bones such as the pelvis, femur, tibias, and feet. There have been several attempts to develop a database for the lower extremities [10-12]. The model of Brand et al. [12] is used in this study because they provide a full database of the 43 muscles. The attachment points of each muscle are described based on the coordinates of the attached bone. The graphically reconstructed model of muscles and each coordinate of the bone are shown in Figure 2. Unlike the given coordinates in Brand et al., the coordinates for the femur are divided into the proximal and the distal in order to determine the fracture position. The coordinates of the force sensor are added to calculate the muscle forces and moments at the position of the force sensor, which will be compared to the force measured in real-time. 

The linear approximation is also able to describe creep and stress relaxation experiments in suspended cells (e.g., leukocytes) and several types of anchorage-dependent cells [Koay, 2003 Sato, 1990]. Taking the continuum theory to another level of complexity, the cytoplasm may be considered to consist of both solid polymeric contents and interstitial fluid. Then it will be appropriate to treat the two phases separately as in the biphasic model [Humphrey, 2001], This model has been widely used to study musculoskeletal cell mechanics, especially single chondrocytes and their interaction with the extracellular cartilage matrix [Shieh, 2002 Shieh, 2003], However, the biphasic theory and irregular geometry often render analytical solution too challenging [Shieh, 2003]. 

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