Portable limb-load monitor utilizing a thin capacitive transducer

We describe a self contained electronic device for controlling the limb loads exerted by patients having one affected foot and using a walking aid. The device measures the limb load with a thin capacitative transducer attached to the sole of the patient's shoe, and operates in two basic modes. In the first mode the device compares the load with two preset thresholds and emits audible feedback tones to guide the patient in maintaining the required load on his affected foot; a low frequency tone when the load falls between the two thresholds, and a high frequency tone when the load exceeds the upper threshold. Experimental results demonstrate the effectiveness of the device in controlling the limb load in the first mode. In the second mode, only one threshold is preset. When the load exceeds that threshold and is maintained above this level for a period longer than a selected stance-duration time, a low-frequency tone is generated.