Measuring and testing – Orthopedic pressure distribution
Patent
1995-09-13
1997-10-21
Cuchlinski, Jr., William A.
Measuring and testing
Orthopedic pressure distribution
128779, A61B 5103
Patent
active
056784481
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates generally to foot pressure sensors and more particularly to a system that may be employed by orthopedic surgeons, their patients, physical therapists, athletes, coaches, trainers, and others to measure forces applied by the foot.
BACKGROUND OF THE INVENTION
Controlling the weight placed on an affected leg while moving about can prevent injury and speed recovery of patients recovering from certain trauma or orthopedic procedures. A person is able to perceive a changing relative weight on a foot, but cannot reliably sense how much constant weight is actually being loaded. That is, an individual's own senses cannot reliably detect how much actual constant weight he or she is placing on a foot. This essential weight information must therefore be provided by some type of external or artificial device.
Forces applied by the foot are not always evenly distributed over the entire surface or sole of the foot. They are usually, but not always, concentrated at the heel or ball of the foot, and they are also usually not applied to these two areas at the same time. A typical walking or running foot strike first loads the heel and then the ball of the foot. In other situations, such as when performing an athletic maneuver, the weight placed on the foot will shift in different patterns. The specific location on the sole of the foot where forces are present, the times at which those forces occur, and the magnitude of those forces are of interest in a number of situations.
Many devices have been designed to measure forces applied by the foot. These include devices for measuring applied forces that are coincident with the position of the leg and body during walking or running, for measuring peak pressure to alert sensory impaired individuals such as diabetics, for measuring the total force applied by the foot, and for measuring forces applied by certain areas of the foot for various purposes.
Such foot force measurement devices are typically heavy and cumbersome and, thus, act to restrict the wearer's movements. Devices which employ an electronic package strapped to the wearer's leg above the ankle and electrically connected to a foot sensor require extra effort when attaching or removing the device. Although this extra effort may seem insignificant, it is nevertheless an inconvenience that may prompt wearer's of such devices to neglect their use. Further, these bulky devices chafe the wearer's skin, are prone to snagging, and are subject to failure resulting from stress on the electrical cable that connects the electronic package to the foot sensor. Other devices employ a stationary foot sensor pad and are therefore only suited for use in a laboratory.
All of the known foot force measurement devices function to convert mechanical force into a suitable signal medium, usually electrical signals. Consequently, the devices can be conveniently categorized according to the type of sensor used to convert changes in mechanical force to changes in electrical signals. Accordingly, these types of sensors include pneumatic or hydraulic fluid activated switches, strain gauge sensors that respond to mechanical deformation, single direct electronic force sensors, multiple direct electronic force sensors with random spacing, and multiple direct electronic force sensors with regular spacing.
Pneumatic and hydraulic sensors are prone to produce inaccurate readings because changes in internal pressure are not necessarily proportional to changes in force. An accurate hydraulic sensor can be constructed if the fluid is displaced from a containing structure which itself, not the fluid, supports the applied forces, and the force required to activate a switch or sensor is very small compared to the force being measured. Exemplary of such sensors are those taught in German patent 3631-923-A to Ernst and in U.S. Pat. No. 3,974,491 to Sipe. Another way to construct an accurate fluid sensor is to use rigid plates which limit the applied force to a constant area of fluid contact, as taught in U.S. Pat.
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Fullen George R.
Fullen Jeryl G.
Cuchlinski Jr. William A.
Fullen Systems, Inc.
Worth Willie Morris
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