Surgery – Diagnostic testing – Measuring anatomical characteristic or force applied to or...
Reexamination Certificate
1999-10-25
2001-05-15
O'Connor, Cary (Department: 3736)
Surgery
Diagnostic testing
Measuring anatomical characteristic or force applied to or...
Reexamination Certificate
active
06231525
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a device for measuring both the absolute and relative muscular strength of the hand digits innervated by the median and ulnar nerves. In addition, the present invention provides a method by which the ratiometric strengths of the digits may be used to distinguish between repetitive motion injuries such as Carpal Tunnel Syndrome (CTS) and other neural or trauma induced injuries.
BACKGROUND OF THE INVENTION
Repetitive motion disorders such as carpal tunnel syndrome are the most common occupational illnesses being reported among a wide range of professions which involve significant hand/wrist motions such as typists (particularly forceful typists), meat cutters, etc. Carpal tunnel syndrome (CTS) symptoms include decreased strength; paresthesias (burning or tingling) in the thumb and adjacent fingers; pain in the wrist, palm, forearm; decreased median nerve conduction velocities; and sensory loss in areas of the hand innervated by the median nerve.
Symptoms resembling CTS may be due to chronic diseases such as rheumatoid arthritis or diabetes mellitus; congenital defects; acute trauma; age; birth control pill usage; and pregnancy. Historically, to aid in the diagnosis of the symptoms, Tinel's Sign, Phalen's Test, and Electromyography nerve conduction tests are usually conducted. Additional tests have been developed to aid in symptom diagnosis which are based on specific measurable parameters such as: the expected weakness of the diseased hand; the decreased sensitivity of the fingers to applied vibrational stimulus; restricted range of motion; sensitivity to applied pressure and chemical analysis of body proteins.
By lightly percussing the course of the median nerve for several seconds, a tingling sensation may be felt in the distribution of the median nerve, indicating a positive Tinel's Sign that suggests that CTS may be present. Phalen's Test generally requires the patient to press the backs of both hands together forming right angles, or holding the patient's wrist in acute flexion for 60 seconds. Numbness or tingling developing over the distribution of the median nerve is an indication that CTS is possible. Positive results in these tests are usually followed by electromyography (EMG) nerve conduction studies. An EMG is sensitive enough to detect the syndrome in 85% of those tested. However, a positive test result cannot be achieved in cases where the nerve has not been damaged to the extent that conduction has been impaired.
Presently, objective clinical information regarding the structure and functionality of the nervous system may be collected by recording electrical signals generated or propagated through the muscular or neural paths of interest. These electrodiagnostic tests require electrodes to be affixed to the patient under study so that electrical signals passing through the area of study may be collected and recorded. In general, these systems require the use of electrodes for both collection and stimulation, which may cause surface burns and/or pain to the patient during the evaluation. Two safety issues are present when using these tests: patient/practitioner contamination due to blood born infection, and possible electrical shock. Both of these hazards may be minimized through disposable electrodes and through proper electrical shielding to make the systems “touch- proof” (shock-proof).
To significantly augment the present electrodiagnostic methods, a methodology relying on totally different physics is necessary. The prior art, not relying on the art of electrodiagnostics, discloses several devices which measure a variety of parameters which are intended to provide evidence of injury, specifically CTS. These prior devices fall into distinct categories which rely or different physical concepts or address specific symptoms. These groups are:
Muscle Strength: Device measures the strength of the finger(s), thumb, or the whole hand grip.
Vibration Threshold: Device measures the threshold of the finger's sensitivity to applied vibrations.
External Pressure: Device applies an external pressure to the appropriate nerve pathway and then asks for subjective report of numbness or weakness.
Body Mobility: Device assesses range of motion in conjunction with EMG testing;
Chemical Analysis: Body fluids are extracted and analyzed via electrophoresis or immunoassay to measure relative amounts of proteins which may be used to infer injury.
U.S. Pat. No. 4,774,966 describes a muscle strength measurement. This device is intended to provide an objective method to measure any weakness present in the hand. If present, this weakness might be related to carpal tunnel syndrome and as such, provide an early identification of the problem. This measurement is accomplished by measuring the strength of the intrinsic hand muscles innervated by the median nerve after it passes through the carpal tunnel. The motion of the hand is limited by the fixture provided such that only the muscles supplied by the median nerve are measured. The test provides a screening by comparing the strength measured to a predefined normal strength. If the test individual should indicate weakness, further evaluation would be indicated. Weakness could be due to peripheral neuropathy, cerebral damage, cervical cord damage and neuromuscular disease.
U.S. Pat. No. 5,163,443 describes a muscle strength measurement. This invention provides for the measurement of applied forces exerted by the hand, wrist and forearm with the intention of detecting the presence of cumulative trauma disorders, such as CTS. The forces measured are correlated with forces expected or required in specific work tasks, by comparing maximal strength as well as mobility of the limb in question. In addition, the system will provide a grip and finger strength measurement. These measurements are made by a single transducer.
U.S. Pat. No. 5,471,996 describes a muscle strength measurement. This patent describes an apparatus which allows a measurement of the muscle strength of the thumb to be studied. Assessment of the strength of the abductor pollicis brevis is important in the diagnosis of some types of neck and elbow injuries, and for CTS and other hand disorders. This apparatus restrains the hand and allows restricted movement to guarantee a reproducible force is applied by the thumb. Isometric and isokinetic testing is possible with this apparatus.
U.S. Pat. No. 5,002,065 describes a vibration threshold measurement. Nerve injury may be induced by exposure to excessive vibration, causing the sensory threshold to be increased for the afflicted fingers. It has also been suggested that an increase in the perception threshold for vibration stimuli is the earliest detectable objective sign in patients with CTS. This patent teaches that serious injury caused by exposure to vibration may be prevented by predicting the injury to the hands prior to irreversible damage by observing the patient's threshold to vibrational stimuli. This same method may be used to measure sensory disturbances such as CTS. This invention provides for the application of a normalized vibrational stimulus to a finger of the patient. The frequency and amplitude of the stimulus are discrete and variable. As the test ensues and the frequency/amplitude are increased, the patient is requested to indicate the onset of sensory perception of the stimuli. The patient is also asked to indicate the loss of detection of the stimuli while the frequency/amplitude sweep is decreasing. The patent addresses the conditions of hand position, temperature, and uniform pressure during testing.
U.S. Pat. No. 5,230,345 describes a vibration threshold measurement. This patent provides for a system and method for detecting CTS in a patient by utilizing a vibratory waveform having a discrete frequency and a variable amplitude. The waveform is applied directly to the finger via contact with a speaker cone. A single finger is measured during the test procedure. When the stimuli is detected by the patient, the patient “clicks” the mous
O'Connor Cary
Szmal Brian
LandOfFree
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