1. Technical Field
The present invention relates generally to medical diagnostic devices and more specifically it relates to a device for testing sensation by means of placing a vibratory apparatus against a human body part.
2. Description of Prior Art
The present invention discloses a vibratory device to be placed onto a human body part, such that the perception (or lack of perception) of the vibrations by the human subject indicates a degree of sensitivity to touch in that body part. Such testing is useful in diagnosing peripheral neuropathy in the extremities, such as the feet. Peripheral neuropathy (i.e., damage to nerves of the peripheral nervous system) is a common cause of foot ulcers in diabetics, resulting in the loss of protective sensation. A frequent consequence of diabetic foot ulcers is lower extremity amputation. It is well established that diabetic foot ulcers precede amputation in most instances. The Center for Disease Control and Prevention recently estimated the prevalence of diabetes in the United States at 8% of the population. The World Health Organization forecasts that the worldwide prevalence of diabetes will double by the year 2030. In light of these staggering numbers and their attendant human and financial costs, a concerted effort is under way to treat diabetes and prevent its subsequent complications.
Simple screening tests for diabetic peripheral neuropathy have been performed for decades to assess sensation in the feet of diabetic patients. The goal of these tests is to appropriately identify those patients with a loss of protective sensation. Once the diagnosis is made, preventative interventions such as palliative podiatric care, specialized shoe wear, and surgery can be initiated. These interventions can prevent diabetic foot ulcers which lead to subsequent infections, hospitalizations and amputations.
The two most common screening tools are the Semmes-Weinstein 10 gram nylon monofilament and the 128 Hertz tuning fork. The nylon monofilament is designed to buckle when 10 grams of force is applied to the skin. The test is performed on various anatomic locations on the bottom of the patient's foot. If the patient is unable to perceive the monofilament at any location, they are deemed to have a loss of protective sensation putting them at risk for foot ulcers. Although the use of this test is widespread, its accuracy and validity have been called into question. It has long been known that nylon monofilaments undergo fatigue with use, rendering them unable to consistently apply 10 grams of pressure. Another complicating factor is the frequent presence of calluses on the bottom of a patient's feet which falsely can mimic neuropathy when only slight pressures are applied.
The 128 Hz tuning fork is an alternative to the nylon monofilament test. It has also been used for decades to assess diabetic peripheral neuropathy and is generally known to be more sensitive than other screening methods. The test is conducted by striking a tuning fork on a solid object and then touching the base of the tuning fork to a bony prominence on the patient's foot. The patient will then perceive (or not) a vibration which gradually subsides over time. The patient tells the clinician when they are no longer able to perceive the vibrations. If the clinician can still feel the vibrations after the patient cannot, then the patient is deemed to have diminished vibratory sensation. Research has shown that patients who are able to feel the tuning fork vibrations for four seconds or less have severe diabetic peripheral neuropathy and are at risk for foot ulceration. Because the vibrations from the tuning fork will propagate through tough or callused skin, use of this test avoids the significant disadvantage of the monofilament test. A tuning fork will also not degrade as will a nylon monofilament, so it can be used over and over without need for replacement.
Despite the better accuracy of the tuning fork test, the use of traditional tuning forks involves an unacceptable degree of subjectivity. Specifically, the force of the initial strike of the tuning fork against the solid object will vary from clinician to clinician and even from one administration of the test to another by the same clinician. The pressure of the end of the tuning fork against the body part may also vary. Either or both of these factors can impact the strength of the initial vibration and thus the time of subsidence of the vibration (whereby a stronger initial vibration will be felt for a longer period of time than a weaker initial vibration). Finally, the exact time of sensation is difficult to precisely determine, either because a simple wall clock is used or another person is required to operate a stop watch.
One device used in an attempt to remove subjectivity from the tuning fork test is known as a biothesiometer. A biothesiometer is a sophisticated vibration testing device involving a contact component, a meter, and an external power supply. It electronically controls a vibration, having means for adjusting the amplitude to determine a sensory threshold. The user either sets a predetermined amplitude and determines whether the patient perceives sensation, or sets the device to either a low amplitude or a high amplitude and then either increases or decreases the amplitude, as appropriate, until the patient first perceives the sensation or stops perceiving the sensation. While the use of a biothesiometer is considered the gold standard in vibration testing, because of its expense and complexity it is little used in most medical offices.
It is therefore shown that there is a need for an improved device for administering a vibratory sensation test having the advantages of the traditional tuning fork test while minimizing the subjectivity inherent in traditional tuning fork tests.
It is therefore an object of the present invention to provide an improved device for administering a vibratory sensation test to a portion of the human body.
Another object of the present invention is to provide an improved device that provides the advantages of a traditional tuning fork test.
Another object of the present invention is to provide an improved device that provides a uniform initial vibration each time it is utilized.
Another object of the present invention is to provide an improved device that provides a uniform degradation of vibration over time each time it is utilized.
Another object of the present invention is to provide an improved device that is integrated with a timer.
Another object of the present invention is to provide an improved device that provides quantifiable, objective information to the clinician.
Another object of the present invention is to provide an improved device that is easy to use.
Another object of the present invention is to provide an improved device that is easy and inexpensive to manufacture.
Other objects and advantages of the present invention will become obvious to the reader and it is intended that these objects and advantages are within the scope of the present invention. To the accomplishment of the above and related objects, this invention may be embodied in the form illustrated in the accompanying drawing. Attention being called to the fact, however, that the drawing is illustrative only, and that changes may be made in the specific construction illustrated and described within the scope of this disclosure.