Technical
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1NG
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Email: info@havsscreening.co.uk
Hand Arm Vibration Syndrome - Clinical Information
Introduction
Hand arm vibration is a widespread hazard, with over one million UK workers exposed to vibration over the HSE action limit 2.8m/s2. At present at least 300,000 workers have reported symptoms of Hand Arm Vibration Syndrome (HAVS). HSE guidance (HSG88) states that up to 10% of exposed workers will develop symptoms of blanching, based on exposure to 2.8m/s2 for 8 years. HAVS is the most common disease assessed by the DSS and is the most common disease reported under RIDDOR.
The excessive exposure to hand held vibrating tools can cause damage to nerves, impair blood circulation, and cause musculoskeletal damage. The symptoms associated with HAVS include numbness, tingling, pain and subsequent reduced dexterity of the hands.HAVS Assessments
HAVS Screening Ltd is now able to offer medical assessments for HAVS.
The Clinical Examination
The clinical examination consists of a history questionnaire and a full examination of fingers, hands and upper body. It is performed by an experienced medical practitioner.
Initially the exposure history is assessed, together with a general overview of how the hands are affected. Whilst assessing the vascular component, the hands are examined and the subject is asked if whiteness or blanching occurs. The Griffin scoring system is used to assign a blanching score. The sensorineural component assesses if tingling and/or numbness occurs, and if there is loss of dexterity. The past medical history is taken, and includes any injury to the neck and upper body, heart/circulation ill health and nerve problems. A full list of current medications is taken with daily smoking and alcohol consumption.
The full examination consists of the following tests:blood pressure for both right and left sides
examination of hands, fingers, wrists and forearms
Allen's Test - demonstrates the integrity of the radial and ulnar arteries of the hands and fingers
Tinel and Phalen's Test - these tests are used to elicit symptoms of carpal tunnel compression. Therefore the complaint of tingling during these tests is indicative of compression of the median nerve under the carpal ligament
Adson's Test - detects any obstruction to the arterial flow to the arm at the level of the neck
Purdue Pegboard - assesses the dexterity of the hand/fingers
Grip strength - assesses the muscle strength of the hand.The Standardised Tests
The physiological standardised test panel consists of three tests designed to assess nerve and blood vessel damage to the hands. There are two nerve systems in the hand, the median and the ulnar. In order to test both systems the index finger (innovated by the median nerve) and the little finger (innovated by the ulnar nerve) of both hands are tested.
There are two tests used to assess nerve damage. The Thermal Aesthesiometry (TA) requires a subject to press a response button when they can detect a temperature change when a fingertip is placed on a metal plate, and the plate either warms or cools. From these responses the hot and cold thermal perception thresholds are calculated. The cold threshold is subtracted from the hot threshold giving the Temperature Neutral Zone (TNZ). This TNZ is the range of temperature which the subject can not detect. The more damage to the nerves of the hand and fingers, the larger the TNZ.
The Vibrotactile Threshold (VTT) is similar to the TA, except the subject is asked to respond when they can detect a vibration in their fingertip. Two vibration frequencies are used in order to assess the damage to two different receptors in the skin. One for the touch sensors and another for the pressure sensors. From these responses the vibration perception threshold is calculated. The more damage to the nerves in the hands and fingers, the higher the VTT.
The Cold Provocation Test (CPT) is used to assess damage to the blood supply in the finger. During this test thermocouples for measuring skin temperature are attached to the subject's fingertips. The hand is cooled in cold water (15°C) for 5 minutes and then allowed to rewarm at room temperature for a period of 10 minutes. During this time the finger skin temperature is measured and the time taken for the fingertip to rewarm 4°C is recorded. This test is a sensitive measure of blood vessel damage. The more damage present in the blood vessels of the fingers, the longer the time taken for them to rewarm.
Classification of HAVS
The Stockholm Workshop scales are used to classify HAVS. This classification system takes into account the vascular and the neurological symptoms of HAVS, as it is recognised that these two components of the disease can progress independently although usually concurrently.The test results are used to support the diagnosis of any damage. The results are scored for both the left and right hands. Using these scores and the results of the clinical examination, the doctors use the Stockholm Workshop scales, and each hand is staged for the vascular and neurologic component.