A new method for the measurement of normal pressure between amputation residual limb and socket.

Present address : Orthopaedic Workshop "Anna Kliniek", Mezenstraat 2, 2333 Leiden, the Netherlands. b Present address : Prins Frisolaan 20, 7242 GZ Lochem, the Netherlands. « Laoummimsveuuovs, unxmrsn~ pa,/s xx INTRODUCTION The measurement of normal pressures at an interface is a universal problem in prosthetics (1, 2, 3). One difficulty is that the existing pressure pattern is disturbed by the sensor placed at the interface . A second problem is that, in general, the interface between the residual limb and the socket is not Ua1, but may be either concave or convex. The first problem is often solved by countersinking the sensor in the socket wall . This, of course, requires removal of materiul from the socket wall,and if measurements were to be made at a large number of places in the socket, lasting damage might be done to the socket . For this reason, we decided to develop a sensor which can stick to the inner surface of the socket wall . In order to disturb as little as possible the existing pressure pattern, such a sensor should be very thin. The second problem (of the curved interface) could be solved by making the sensor flexible. We have not succeeded in finding a transducer which can be placed at the interface while satisfying the abovementioned requirements. Therefore, we have chosen a solution in which the pressure is transmitted first in the form of a hydraulic pressure signal . This hydraulic pressure is then measured with a transducer outside the socket, where more space is available. This has been schematically represented in Figure 1.