Vibrotactile sense and hand symptoms in blue collar workers in a manufacturing industry

Applied Force Alters Sensorineural and Peripheral Vascular Function in a Rat Model of Hand-Arm Vibration Syndrome

OBJECTIVE

This study described the effects of applied force (grip) on vascular and sensorineural function in an animal model of hand-arm vibration syndrome (HAVS).

METHODS

Rat tails were exposed to 0, 2, or 4 N of applied force 4 hr/d for 10 days. Blood flow and sensitivity to transcutaneous electrical stimulation and pressure were measured.

RESULTS

Applied force increased blood flow but reduced measures of arterial plasticity. Animals exposed to force tended to be more sensitive to 250-Hz electrical stimulation and pressure applied to the tail.

CONCLUSIONS

Effects of applied force on blood flow and sensation are different than those of vibration. Studies examining co-exposures to force and vibration will provide data that can be used to determine how these factors affect risk of workers developing vascular and sensorineural dysfunction (ie, HAVS).

Pain mechanisms in carpal tunnel syndrome: a systematic review and meta-analysis of quantitative sensory testing outcomes

ABSTRACT

Carpal tunnel syndrome (CTS) is the most common nerve compression in the arm. A mix of peripheral and central contributions on quantitative sensory testing (QST) has been reported in the literature. Thus, this systematic review or meta-analysis aimed to identify the dominant sensory phenotype and draw conclusive evidence about the presence of central sensitization (CS) in CTS. Based on an a priori published protocol and using PRISMA guidelines, 7 databases were searched (Embase, Web of Science, Scopus, PubMed, SAGE, EBSCOhost, and ProQuest). Eligible studies compared the QST findings of individuals with subacute and chronic CTS with those of healthy controls through thermal, mechanical, and vibration detection thresholds; thermal, pressure, and mechanical pain thresholds; mechanical pain sensitivity; presence of allodynia; wind-up ratio; and conditioned pain modulation. Thirty-seven studies were included in the qualitative analysis. Results showed a significant loss of all detection thresholds of hand median nerve territories and hand extramedian areas (little finger and hand dorsum) in CTS (P < 0.05) but no significant difference (P > 0.05) in wind-up ratio, cold, heat, or mechanical pain thresholds of the median nerve territories. Furthermore, there was a significant increase in mechanical pain sensitivity in median nerve territories and remotely in the forearm (P < 0.05) and a significant gain in pressure and heat pain thresholds in the carpal area (P < 0.05). Conditioned pain modulation was impaired in CTS. Hypoesthesia and increased thermal and mechanical pain ratings are the dominant sensory phenotype with inconclusive evidence about CS in CTS due to the heterogenous results of thermal and mechanical pain thresholds.

A Review of Hand-Arm Vibration Studies Conducted by US NIOSH since 2000

Studies on hand-transmitted vibration exposure, biodynamic responses, and biological effects were conducted by researchers at the Health Effects Laboratory Division (HELD) of the National Institute for Occupational Safety and Health (NIOSH) during the last 20 years. These studies are systematically reviewed in this report, along with the identification of areas where additional research is needed. The majority of the studies cover the following aspects: (i) the methods and techniques for measuring hand-transmitted vibration exposure; (ii) vibration biodynamics of the hand-arm system and the quantification of vibration exposure; (iii) biological effects of hand-transmitted vibration exposure; (iv) measurements of vibration-induced health effects; (iv) quantification of influencing biomechanical effects; and (v) intervention methods and technologies for controlling hand-transmitted vibration exposure. The major findings of the studies are summarized and discussed.

Cold Intolerance in the Hand - An Unsolved Problem

Cold intolerance in the hand is a big problem for patients after nerve- and vascular injuries. The purpose of this paper is to emphasise how important and necessary it is that hand therapists consider this phenomenon in the evaluation of hand function after nerve injuries, and that further developmental work and research are needed in this important area.

The Hand-Arm Vibration International Consortium (HAVIC): Prospective Studies on the Relationship Between Power Tool Exposure and Health Effects

OBJECTIVES

The Hand-Arm Vibration International Consortium (HAVIC) is a collaboration of investigators from Europe and North America studying health effects from hand-arm vibration (HAV). Features include prospective design, cross-cohort exposure, and health assessment methods.

METHODS

Two new cohorts (dental hygienists and dental hygiene students), two existing cohorts (Finnish forest workers, and Swedish truck cab assemblers), and a previous population (US shipyard workers) are included. Instruments include surveys, quantitative medical tests, physical examination, and work simulation and data logging to assess exposure. New methods were developed for nerve conduction and data logging.

RESULTS

Findings on the relationship between nerve conduction and skin temperature in HAV-exposed subjects resulted in a new approach to subject warming.

CONCLUSIONS

Integrating established cohorts has advantages over de novo cohort construction. Complex laboratory tests can be successfully adapted for field use.

Impaired manual dexterity and neuromuscular dysfunction in patients with hand-arm vibration syndrome

Manual dexterity and hand functional difficulties in daily life in hand-arm vibration syndrome (HAVS) were investigated in 29 male patients with HAVS and 30 male controls without occupational exposure to hand-arm vibration. Manual dexterity was assessed by measuring the performance time of picking up and transferring 30 red beans, one by one, from one plate to another. Vibrotactile perception thresholds at 125 Hz and grip strength were also examined. Hand functional difficulties in daily life were surveyed with a questionnaire. The HAVS patients had an increased vibrotactile threshold, decreased grip strength, and low performance in transferring beans. Low performances with transfer times over 53 s (2SD from the mean in the controls) were found in 66% of the HAVS patients and 3% of the controls. Bean transfer times in the patients were correlated with an increasing vibrotactile threshold and decreasing grip strength. The transfer times of the patients were also associated with hand functional difficulties such as picking up coins, turning the pages of a newspaper, buttoning clothes, and pouring from a teapot. The patients with a prolonged transfer time over 60 s (3SD from the mean in the controls) were most likely to have hand functional difficulties. The present findings suggest that measurement of the bean transfer time will serve to assess manual dexterity among HAVS patients, and that impaired manual dexterity in patients may be associated with impaired sensory feedback and muscular dysfunction in the fingers and hands.

Hand muscle pathology after long-term vibration exposure

The morphology of the abductor pollicis brevis muscle was studied in 20 patients suffering from hand-arm vibration syndrome. The main morphological changes observed were centrally located myonuclei and fibre type grouping (found in all 20 muscle biopsies), angulated muscle fibres (found in 19 biopsies), ring fibres and regenerating fibres (found in 18 biopsies) and fibrosis (found in 17 biopsies). The observed abnormalities are believed to reflect damage to both the muscle fibres and the motor nerve. The changes were related to different vibration exposure parameters. The number of fibres demonstrating centrally located nuclei correlated significantly with the cumulative vibration exposure, while the number of angulated fibres correlated significantly with the total vibration exposure time. This indicates that the vibrating tools may cause direct damage to muscle fibres as well as nerves.

Digital vibration threshold testing and ergonomic stressors in automobile manufacturing workers: a cross-sectional assessment

Upper extremity musculoskeletal disorders (UEMSDs) comprise a large proportion of work-related illnesses in the USA. Physical risk factors including manual force and segmental vibration have been associated with UEMSDs. Reduced sensitivity to vibration in the fingertips (a function of nerve integrity) has been found in those exposed to segmental vibration, to hand force, and in office workers. The objective of this study was to determine whether an association exists between digital vibration thresholds (VTs) and exposure to ergonomic stressors in automobile manufacturing. Interviews and physical examinations were conducted in a cross-sectional survey of workers (n = 1174). In multivariable robust regression modelling, associations with workers' estimates of ergonomic stressors stratified on tool use were determined. VTs were separately associated with hand force, vibration as felt through the floor (whole body vibration), and with an index of multiple exposures in both tool users and non-tool users. Additional associations with contact stress and awkward upper extremity postures were found in tool users. Segmental vibration was not associated with VTs. Further epidemiologic and laboratory studies are needed to confirm the associations found. The association with self-reported whole body vibration exposure suggests a possible sympathetic nervous system effect, which remains to be explored.

Normative vibrotactile thresholds measured at five European test centres

OBJECTIVES

To compare vibrotactile thresholds between five international test centres, to determine causes of variability, and to provide normative data for use by health professionals.

METHODS

Vibrotactile thresholds were measured on various fingers in 1,008 subjects at 31.5 Hz (2,531 measurements) and at 125 Hz (2,807 measurements). Three centres used the up-and-down method of limits, rate of change of stimulus 3dB/s, to obtain vibrotactile thresholds. The push force on the surround was 2 N, the probe contact force was 1 N and the probe diameter was 6 mm concentric to a 10-mm diameter hole in the surround. One centre used an up-and-down method of limits with a 5-dB step and a 1.26-mm diameter probe with no surround. Another centre used a stepping algorithm, no surround, and the force on the 6-mm-diameter probe was unspecified.

RESULTS

The 31.5-Hz thresholds and 125-Hz thresholds, expressed in dB, were similar between centres using similar methods. There were small (<5 dB) differences in vibrotactile thresholds between male and female subjects, between white-collar and blue-collar workers and between fingers. Both 31.5-Hz and 125-Hz thresholds increased with age; the mean effect of age on 31.5-Hz thresholds was approximately 2 dB over 25 years, while the effect of age on 125 Hz-thresholds was as high as 10 dB over 25 years.

CONCLUSIONS

Vibrotactile thresholds are influenced by measurement method but can be similar at different centres if similar methods are used. Effects of measurement location and gender are often negligible. Thresholds depend on age, but over the range of ages considered, only the effect on 125-Hz thresholds is sufficient for correction; methods of correcting for age are given. These normative data may be used to assist the diagnosis of peripheral neuropathy involving vibrotactile sensation.

Effects of whole body cooling on sensory perception and manual performance in subjects with Raynaud's phenomenon

Patients with Raynaud's phenomenon (RP) have abnormal digital vasoconstriction in response to cold. The aim of the study was to investigate the effects of cooling on sensory perception and manual performance in healthy male subjects and subjects with RP. There were two groups of subjects with primary RP: 12 subjects fulfilled the criteria of Lewis (L) and the other 12 the more critical criteria of Maricq (M). Control group (C) consisted of 19 healthy men. Subjects were exposed to 5 degrees C for 60 min. Skin temperatures were measured. Finger dexterity, pinch strength, abduction/adduction of fingers, pressure perception threshold and vibration perception threshold were tested during the exposure every 15 min. At the beginning of the exposure the mean (S.E.) finger temperature was 2.5 (1.2) degrees C (P<0.05) lower in M than in C. Manual performance and sensory perception were impaired due to the cooling, the impairment being significantly greater in M than in C. Responses of L were between those of M and C. In a given finger temperature vibration and pressure sensibility and manual performance were lower in M and L than in C. In conclusion, cold exposure decreased sensory perception and manual performance in the subjects with RP to a lower level than in the healthy subjects. Non-thermal factors may also decrease performance in RP.

Agreement between clinical examination and quantitative tests of neurologic function among 384 subjects

BACKGROUND

Quantitative neurological tests are often cheaper and easier than clinical examinations, and provide continuous data which may discriminate between exposed and nonexposed groups with more sensitivity than dichotomous (normal/abnormal) examination data.

METHODS

We compare clinical examinations and analogous quantitative tests for arm tremor, postural sway, and vibrotactile sensitivity (finger and toe), for 384 subjects.

RESULTS

The "abnormal" clinical outcomes studied were relatively common (range, 3-36%), and did not result in impairment of daily activity for affected subjects. All the quantitative tests were reasonably good predictors of the corresponding clinical outcome. The most predictive test was for toe vibrotactile sensitivity. The probability of an abnormal clinical result for those in the worst quartile for the toe test was 0.63, compared with 0.36 for all subjects.

CONCLUSIONS

Our results suggest that certain quantitative tests might be used in epidemiologic studies instead of a physical examination.

Risk of hand-arm vibration syndrome according to occupation and sources of exposure to hand-transmitted vibration: A national survey

BACKGROUND

Although some occupational sources of hand-transmitted vibration (HTV) have been extensively investigated, the risks associated with others are poorly characterized.

METHODS

A questionnaire was mailed to a community sample of 12,240 men aged 16- 64 years and 906 men from the armed forces. Questions covered current occupation, sources of HTV, numbness or tingling in the fingers in the past week, and finger blanching. In the 5,364 respondents who had been at work in the past week, associations between symptoms and exposures were examined by logistic regression, with odds ratios converted into prevalence ratios (PRs).

RESULTS

Altogether, 513 men (10%) reported cold-induced finger blanching and 769 (14%) sensory symptoms in the fingers. The risk of blanching was increased in builders (PR 2.4, 95% CI 1.0-5.2), carpenters and joiners (PR 1.9, 95% CI 1.0-3.4), motor mechanics (PR 2.3, 95% CI 1.1-4.6), and laborers (PR 2.8, 95% CI 1.3-6.0); while the risk of sensory symptoms was elevated in laborers (PR 4.0, 95% CI 2.3-6.6) and plant operatives (PR 3.5, 95% CI 1.9-5.9). Use of hand-guided mowers, concrete breakers, chain saws, and jig saws was significantly associated with symptoms.

CONCLUSIONS

Little attention has been paid to the risks of vibration injury in construction workers, woodworkers, motor mechanics, and laborers, or to the risks from mowers, jig saws and several other common vibratory tools. These should be a focus for further investigation and preventive measures.

The prevalence of sensorineural symptoms attributable to hand-transmitted vibration in Great Britain: a national postal survey

BACKGROUND

Exposure to hand-transmitted vibration (HTV) can cause sensorineural symptoms in the upper limb, but its impact has not previously been assessed in the general population.

METHODS

To investigate, we mailed a questionnaire about exposures to HTV, finger blanching and sensory symptoms (numbness or tingling) in the upper limbs to a population sample comprising 21,201 working-aged men and women selected at random from the age-sex registers of 34 British general practices, and a further 993 randomly selected from the pay records of the armed services. Associations were explored using multiple logistic regression models to adjust for confounding, with the resultant odds ratios converted into prevalence rate ratios (PRs).

RESULTS

Of 12,907 respondents, 2,607 (20.2%) reported sensory symptoms in the upper limb during the past week. Sensory symptoms were more prevalent in those with blanching, and were commonly associated with exposure to HTV, especially in men. In comparison with men who had never been exposed to HTV, the PR in men exposed both at work and in leisure was 2.2 (95% CI 1.9-2.4). Associations were found even in those who had never blanched.

CONCLUSIONS

Sensorineural symptoms in the upper limbs are common. HTV is an important risk factor for such complaints in the general population.

Exposure-response relationship between hand-arm vibration and vibrotactile perception sensitivity

BACKGROUND

The objectives of the study were to examine whether occupational use of vibrating hand-held tools was associated with an impaired vibrotactile perception, whether any exposure-response relationship exists, and whether the different populations of mechano-receptive afferent units are equally affected.

METHODS

Vibrotactile perception thresholds have been measured at seven frequencies (8-500 Hz) and evaluated among 125 vibration-exposed and 45 non-exposed male employees in a heavy engineering production workshop. Vibration exposure measurements were assessed on tools in accordance with ISO 5349. Vibrotactile perception thresholds have been individually graded in stages and placed in relation to individual vibration exposure.

RESULTS

The outcome did not reveal a clear relationship between vibration exposure and reduced vibrotactile sensitivity on an individual basis. There was a clear tendency on a group basis towards elevated thresholds when the study population was divided into three exposure categories. A fourfold increase in relative risk of reduced vibrotactile sensitivity for test frequencies above 40 Hz was observed between the highest exposure category compared to the non-exposed.

CONCLUSIONS

It was concluded that reduced tactile sensitivity is related to the degree of vibration exposure but it is not at present possible to delineate an exposure-response relationship.