Standardization in Platform Stabilometry being a Part of Posturography.


* ENT department and Department of Neurology, Free University Hospital, Amsterdam
** Department of Mechanical Engineering resp. Physics, University of Technology Eindhoven
and *** Department of clinical Neurophysiology, Hospital St Annadal, Maastricht

Posturography is not a clearly defined subject. Numerous investigators are working in this field being active in technical laboratories, research institutes and medical departments. Dependent on the intention and the focus of interest the problem statement is formulated and the approach is chosen. So rather different types of equipment are used to measure and study postural stability and body movements either spontaneous or with application of stimuli. One aspect of posturography is the recording of body movements of subjects in standing position. In this restricted sense of the word we will speak about stabilometry. A number of quite different methods are practized for the stabiiometric measurements. Without any claim or suggestion about completeness some stricking proves of inventivity will be mentioned. Supposing a certain rigidity in the body a number of authors studied the movements of the head using accelerometers (Tokita, Watanabe and Fukuda, 1972), light beams (Boman and Jalavisto, 1953; Jarrige, 1968; Kapteyn, 1972; Tokumasu and Kawano, 1976), strings (Fearing, 1924) and mechanical structures (Vierordt, 1864; Tokita, Miyata et al., 1976) fixed to the head. Other authors measured the movement of the trunk, also using quite different methods as accelerometers (Thomas and Whitney, 1959) light (Hirasawa, 1973), sound sources (Guegen and Leroux, 1973); Amblard and Cremieux, 1976), strings (Kuhnke, 1950; Smith, 1957; Nashner, 1971 ; Gantchev, Draganova and Dunev, 1972), magnetic coils or video systems (Kapteyn, 1973; Spaepen, Peeraer and Willems, 1979). A less direct method for studying the body stability is the recording of the movement of the body's point of pressure to the foot support using a force measuring platform. The displacement of the point of pressure is not only caused by a possible shift of the body's point of gravity, but also by the acceleration and deceleration forces related to the movements of the inertial mass of the body (Smith, 1957; Scott and Dzendolet, 1972 Guruinkel, 1973; Hla vacka and Litvinenkova, 1973; Kapteyn, 1973; Geursen, Altena et al., 1976; Spaepen, Vranken and Willems, 1978; Massen and Kodde, 1979; Kodde, Caberg and Mol, 1982). The contribution of this dynamic part is at least as large as that of the static part being the effect of the shift of the point of the body's point of gravity. Besides that such a shift can be caused by a movement of the standing subject as such it also can be caused by a change in configuration of the parts of the body in which case the measured shift is not representative for the subjects stability (Corti, 1959). In some platforms the static and dynamic components are separated. (Thomas and Whitney, 1959; Spaepen, Fortuin and Willems, 1979). Some platform are sensitive for horizontal shearing forces as well (Begbie, 1967; Dichgans, Mauritz et al., 1976; Spaepen, Vranken and Willems, 1978).


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