Anatomical coordinate system

Joint Kinematics Reiative Motion between Adjacent Anatomical Coordinate Systems... 

In a subject cahbration, usually performed with the subject standing, additional data are collected by the measurement system that relates the technical coordinate systems to the underlying anatomical structure. For example, as shown in Figure 51.2b, the medial and lateral femoral condyles and the medial... 

FIGURE 76.1 Planes and axes are illustrated in anatomical position. The central coordinate system with its origin between the cornua of the sacrum is shown. (From White III A.A. and Panjabi M.M. 1990. Clinical Biomechanics of the Spine, 2nd ed., p. 87. Philadelphia, JB Lippincott Company. With permission.)... 

Force platforms are used to resolve the load a subject applies to the ground. These forces and moments are measured about X, Y, and Z axes specific to the force platform. In general, the orientation of the force platform axes will differ from the orientation of the reference axes of the object-space. This is illustrated schematically in Fig. 5.14. Thus, it is necessary that the ground reaction forces be transformed into the appropriate reference system before they are used in subsequent calculations. For example, the ground reaction forces acting on the foot should be transformed into the foot coordinate system, if ankle joint forces and moments are expressed in an anatomically meaningful reference system (i.e., about axes of the ACSfooi). 

Orientation of Sensors. Tissue-, interface-, and structure-mounted sensors may be aligned as closely as possible with the axes of a biodynamic coordinate system (see, for example, Fig. 10.2), even though these may have inaccessible origins that are anatomical sites within the body. In practice, sensors are commonly oriented to record the component accelerations defined by the basicentric coordinate systems shown in Fig. 10.2 (ISO 2631-1, 1997 ISO 5349-1,2001), which have origins at the interface between the body and the vibrating surface. The location of accelerometers to record the handle vibration of specific power tools is described in an international standard (ISO 5349-2, 2001). 

Physiologically, in both normal and hypertensive individuals, blood pressure is maintained by moment-to-moment regulation of cardiac output and peripheral vascular resistance, exerted at three anatomic sites (Figure 11-1) arterioles, postcapillary venules (capacitance vessels), and heart. A fourth anatomic control site, the kidney, contributes to maintenance of blood pressure by regulating the volume of intravascular fluid. Baroreflexes, mediated by autonomic nerves, act in combination with humoral mechanisms, including the renin-angiotensin-aldosterone system, to coordinate function at these four control sites and to maintain normal blood pressure. Finally, local release of vasoactive substances from vascular endothelium may also be involved in the regulation of vascular resistance. For example, endothelin-1 (see Chapter 17) constricts and nitric oxide (see Chapter 19) dilates blood vessels. 

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