Sensorineural stages of the hand-arm vibration syndrome

Vocational rehabilitative decisions after symptoms and findings consistent with hand-arm vibration syndrome in the Swedish surveillance system - a mixed-method design

BACKGROUND

EU workers exposed to hand-arm vibration should be offered health surveillance to detect early symptoms, and findings, of Hand-Arm Vibration Syndrome (HAVS). To execute the mandatory vocational rehabilitation, the employer needs to be aware of injuries found in the medical check-up. We aimed to analyse: 1) How physicians graded the neurosensory component of HAVS on the Stockholm Workshop Scale (SWS), compared to semi-objective findings. 2) What vocational rehabilitative decisions (VRD) were taken by physicians after examinations. 3) Whether the VRDs differed in relation to the SWS-grading.

METHODS

Data came from 660 medical records - all examinations performed during twelve consecutive months in one large Swedish occupational healthcare company. 572 individuals had data on the SWS from the physician. For the qualitative analysis, we used the inductive-iterative immersion-crystallization method.

RESULTS

60% of the examined workers had symptoms and 32% had semi-objective findings consistent with HAVS. The physicians' SWS gradings were underestimated in 59% of the cases with semi-objective findings. The VRDs were classified, relative to communication with the employer, as: "Adequate" (57%), when no injury was present, communication had already taken place, was planned, or was no longer needed in the absence of further exposure, "Semi-adequate" (18%), if no plan for communication was yet established or only communicated through a document with a shorter time until next check-up, and "Inadequate"(25%), when patients refused (20%), or physicians failed to communicate with the employer, despite findings (80%). Underestimated SWS-gradings of HAVS were significantly associated with more "Inadequate" VRDs in the group with semi-objective findings.

CONCLUSIONS

Occupational physicians underestimate the number of individuals with SWS 2-3 compared with semi-objective findings and regularly fail to communicate to the employer despite findings of HAVS. The underestimation of SWS-grading, followed by inadequate VRDs, excludes many workers from the employer's mandatory protective measures which may lead to aggravation of an untreatable injury in the affected individual and development of HAVS in their similarly exposed colleagues.

Serum levels of biomarkers related to severity staging of Raynaud's phenomenon, neurosensory manifestations, and vibration exposure in patients with hand-arm vibration injury

Our aim was to explore possible relationships between serum levels of biomarkers in patients with hand-arm vibration injury in relation to the severity of the vascular, i.e., Raynaud's phenomenon (RP), and neurosensory manifestations, the current exposure level, and the duration of exposure. This study was of case series design and involved 92 patients diagnosed with hand-arm vibration injury. Jonckheere's trend test was used to assess any association between serum levels of biomarkers and RP as well as neurosensory manifestations, graded by the International Consensus Criteria. Generalized linear models with adjustment for possible confounders were also used for associations between serum levels of biomarkers and; (1) severity of RP recorded as the extent of finger blanching calculated with Griffin score, (2) vibration perception thresholds, (3) magnitude of current exposure as [A(8); (m/s2)] value, and (4) the duration of exposure in years. Serum levels of thrombomodulin, von Willebrand factor, calcitonin gene related peptide (CGRP), heat shock protein 27, and caspase-3 were positively associated with severity of RP. Serum levels of CGRP were positively associated with the neurosensory component. No associations with exposure were shown for these biomarkers. For Intercellular adhesion molecule 1 and monocyte chemoattractant protein 1, no associations were found with neither severity nor exposure. Levels of serum biomarkers associated with endothelial injury or dysfunction, inflammation, vasodilation, neuroprotection, and apoptosis were positively associated with the severity of hand-arm vibration injury.

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).

Concordance between the Stockholm Workshop Scale and the International Consensus Criteria for grading the severity of neurosensory manifestations in hand-arm vibration syndrome in a Swedish clinical setting

OBJECTIVES

Occupational exposure to vibration using hand-held tools may cause hand-arm vibration syndrome (HAVS). Correct diagnosis and grading of severity are crucial in protecting the individual's health and for workers' compensation claims. The International Consensus Criteria (ICC) has been suggested to replace the widely used Stockholm Workshop Scale (SWS). The aims were to, in a clinical setting, assess the concordance between the SWS and the ICC neurosensory severity grading of vibration injury, and to present the clinical picture according to symptoms, type of affected nerve fibres and the relation between vascular and neurosensory manifestations.

METHODS

Data were collected from questionnaires, clinical examination and exposure assessment of 92 patients with HAVS. The severity of neurosensory manifestations was classified according to both scales. The prevalence of symptoms and findings was compared across groups of patients with increasing severity according to the SWS.

RESULTS

Classification with the ICC resulted in a shift towards lower grades of severity than with the SWS due to a systematic difference between the scales. Affected sensory units with small nerve fibres were far more prevalent than affected units with large nerve fibres. The most prevalent symptoms were numbness (91%) and cold intolerance (86%).

CONCLUSIONS

Using the ICC resulted in lower grades of the severity of HAVS. This should be taken into consideration when giving medical advice and approving workers' compensation. Clinical examinations should be performed to detect affected sensory units with both small and large nerve fibres and more attention should be paid to cold intolerance.

Vibration Isolation Properties of Novel Spacer Fabric with Silicone Inlay

Spacer fabrics are good for impact force absorption and have the potential for vibration isolation. Inlay knitting of additional material to the spacer fabrics can give reinforcement to the structure. This study aims to investigate the vibration isolation properties of three-layer sandwich fabrics with silicone inlay. The effect of the presence of the inlay, inlay patterns and materials on the fabric geometry, vibration transmissibility and compression behaviour were evaluated. The results showed that the silicone inlay increases the unevenness of the fabric surface. The fabric using polyamide monofilament as the spacer yarn in the middle layer creates more internal resonance than that using polyester monofilament. Silicone hollow tubes inlay increases the magnitude of damping vibration isolation, whereas inlaid silicone foam tubes have the opposite effect. Spacer fabric with silicone hollow tubes inlaid by tuck stitches has not only high compression stiffness but also becomes dynamic, showing several resonance frequencies within the tested frequency range. The findings show the possibility of the silicone inlaid spacer fabric and provide a reference for developing vibration isolation materials with knitted structure and textiles materials.

Evaluation of neurological testing for hand-arm vibration syndrome

BACKGROUND

The neurological component of hand-arm vibration syndrome (HAVS) uses the Stockholm Workshop Scale sensorineural (SWS SN) stages for classification. Proximal compressive neuropathies are common in HAVS and the symptoms are similar to SN HAVS. The SWS may not be a valid staging tool if a patient has comorbid proximal compression neuropathy.

AIMS

To evaluate the prevalence of proximal compression neuropathy in patients presenting for HAVS assessment and examine the association between compressive neuropathies and SWS SN.

METHODS

A standardized assessment protocol was used to assess 431 patients for HAVS at St. Michael's Hospital, Toronto, Ontario. The prevalence of median and ulnar compressive neuropathies was determined. The association between proximal compression neuropathies and SWS SN stage (0/1 versus 2/3) was evaluated using Chi-square and Fisher's exact tests as well as multivariable logistic regression.

RESULTS

Most patients (79%) reported numbness and 20% had reduced sensory perception (SWS SN Stage 2/3). Almost half (45%) had median neuropathy at the wrist and 7% had ulnar neuropathy. There was no association between the SWS SN stage and median or ulnar neuropathy.

CONCLUSIONS

Two neurological lesions should be investigated in patients presenting for HAVS assessment: compressive neuropathy and digital neuropathy. The prevalence of compressive neuropathies is high in patients being assessed for HAVS and therefore nerve conduction studies (NCS) should be included in HAVS assessment protocols. Comorbid proximal neuropathy does not affect the SWS SN stage; therefore, NCS and SWS SN seem to be measuring different neurological outcomes in HAVS patients.

The clinical consequence of using less than four sensory perception examination methods in the Swedish surveillance system for Hand-Arm vibration syndrome

OBJECTIVES

The Swedish surveillance system aiming to reveal undetected Hand-Arm Vibration Syndrome (HAVS) in workers exposed for vibrations is regulated by the provision AFS 2019:3. The goal for the surveillance system is to diagnose HAVS, as well as to find workers at risk for developing HAVS due to other conditions. The national guidelines stipulate examination using at least two out of four hand sensory examination methods (SEM); monofilament (touch), two-point discrimination (discriminative), tuning fork (vibrotactile), and Rolltemp (thermotactile). The aim of this study was to examine the clinical consequence of using less than four of these SEMs.

METHODS

We collected data on SEMs from the medical records of all individuals that went through the specific surveillance medical check-up in a large occupational health service for 1 year. We then calculated the number of workers found with HAVS when using one, two, or three SEMs, and compared with the result from using all available SEMs.

RESULTS

Out of 677 examined individuals, 199 had positive findings in at least one SEM. The detection rate for these findings was on average 47% when using one SEM, 71% using two SEMs, and 88% using three SEMs (out of 100% detection when all four SEMs were used).

CONCLUSIONS

If fewer than four sensory examination methods are used for surveillance of HAVS, many workers with incipient injuries may stay undetected. This may lead to further exposure resulting in aggravation of injury.

Serum Metabolites in Hand-Arm Vibration Exposed Workers

OBJECTIVE

To investigate whether low molecular organic biomarkers could be identified in blood samples from vibration exposed workers using a metabolomics.

METHODS

The study population consisted of 38 metalworkers. All participants underwent a standardized medical examination. Blood samples were collected before and after work shift and analyzed with gas chromatography time-of-flight mass spectrometry. Multivariate modeling (orthogonal partial least-squares analysis with discriminant analysis [OPLS-DA]) were used to verify differences in metabolic profiles.

RESULTS

Twenty-two study participants reported vascular symptoms judged as vibration-related. The metabolic profile from participants with vibration-induced white fingers (VWF) was distinctly separated from participants without VWF, both before and after vibration exposure.

CONCLUSION

Metabolites that differed between the groups were identified both before and after exposure. Some of these metabolites might be indicators of health effects from exposure to vibrations. This is the first time that a metabolomic approach has been used in workers exposed to vibrations.

Vibrotactile sensitivity testing for occupational and disease-induce peripheral neuropathies

The International Standard Organization (ISO) standard 13091-1 describes methods and procedures for performing the vibrotactile perception threshold (VPT) testing to diagnose changes in tactile sensory function associated with occupational exposures. However, the VPT test also has been used in the diagnosis of peripheral neuropathies associated with a number of disorders. This review examines the VPT test, variations in procedures that have been used, as well as disorders and diseases in which this test has been reliable for the detection of sensory changes. Mechanisms potentially underlying the changes in VPTs are also discussed along with procedural and subject/patient factors that may affect the interpretation of test results. Based upon the review of the literature, there are also suggestions for where additional research might improve the administration of this test, depending upon the subject/patient population and interpretation of data.

Adverse health manifestations in the hands of vibration exposed carpenters - a cross sectional study

BACKGROUND

Despite EU regulatory standards, many workers suffer injury as a result of working with hand-held vibrating tools. Our aim of this study was to confirm whether carpenters, a highly exposed group, suffer more injuries to their hands than painters, a group assumed to be less exposed to vibration.

METHODS

193 carpenters (participation rate 100%) and 72 painters (participation rate 67%), all men, answered a questionnaire and underwent a clinical examination to identify manifestations of neural and vascular origin in the hands. Neurosensory affection was defined as having at least one symptom in the fingers/hands (impaired perception of touch, warmth, or cold, impaired dexterity, increased sensation of cold, numbness or tingling, or pain in the fingers/hands when cold) and at least one clinical finding (impaired perception of touch, warmth, cold, vibration, or two-point discrimination). Logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

Neurosensory affection was fulfilled for 31% of the carpenters and 17% of the painters, age-adjusted OR 3.3 (CI 1.6-7.0). Among carpenters with neurosensory affection 18% reported interference with daily life activities, the most common symptoms being increased sensation of cold, numbness and pain in the fingers/hands when cold, the most common clinical findings were impaired perception of touch and vibration. Neurosensory affection was found in 12% of young carpenters (≤ 30 years old). No difference was found in the prevalence of white fingers between carpenters and painters.

CONCLUSIONS

Carpenters showed more symptoms and clinical findings of neurosensory affection than painters, probably due to vibration exposure. Also young carpenters showed signs of neurosensory affection, which indicates that under current conditions workers at these companies are not protected against injury. This underlines the importance of reducing exposure to vibration and conducting regular medical check-ups to detect early signs of neural and vascular manifestations indicating hand-arm vibration injuries. Special attention should be given to symptoms of increased sensation of cold, pain in the fingers when cold, and numbness, as these were the most common initiating ones, and should be addressed as early as possible in the preventive sentinel process. It is also important to test clinically for small- and large-fibre neuropathy, as the individual may be unaware of any pathology.

Tremor measurements in a 22-year cohort study of workers exposed to hand-held vibrating tools

OBJECTIVES

The objectives of this cohort study were to evaluate possible long-term effects of occupational exposure to hand-arm vibration (HAV) in terms of increased tremor. The aims were to evaluate whether exposure during follow-up, baseline hand-arm vibration syndrome (HAVS), baseline manual dexterity or current medical conditions or life-style habits might be associated with increased tremor. A further aim was to compare two different activation conditions: postural vs rest tremor.

METHODS

Forty men (current age: 60.4 years) who had previously worked as manual workers in a specialized engineering and construction company enrolled in the study. Their hand functions had been examined in 1994. At the baseline examination, 27 had been diagnosed with HAVS, while 13 were not exposed. The follow-up examination in 2016-2017 comprised the CATSYS Tremor Pen^® for measuring postural and rest tremor and the Grooved Pegboard Test for assessing manual dexterity. Blood samples were taken for assessing biomarkers that might have impact on tremor.

RESULTS

Neither cumulative exposure to HAV during follow-up nor HAVS at baseline were associated with increased tremor. A test for manual dexterity at baseline was significantly associated with increased tremor (Tremor Intensity) at follow-up. Blood markers of current medical conditions and tobacco consumption were associated with increased tremor. Rest tremor frequency was higher than postural tremor frequency (p < 0.001).

CONCLUSIONS

The main findings of this 22-year cohort study were no indications of long-term effects on tremor related to HAV exposure and previous HAVS status. However, baseline manual dexterity was significantly associated with increased tremor at follow-up. Activation conditions (e.g., hand position) are important when testing tremor.

Frequency-dependent changes in mitochondrial number and generation of reactive oxygen species in a rat model of vibration-induced injury

Regular use of vibrating hand tools results in cold-induced vasoconstriction, finger blanching, and a reduction in tactile sensitivity and manual dexterity. Depending upon the length and frequency, vibration induces regeneration, or dysfunction and apoptosis, inflammation and an increase in reactive oxygen species (ROS) levels. These changes may be associated with mitochondria, this study examined the effects of vibration on total and functional mitochondria number. Male rats were exposed to restraint or tail vibration at 62.5, 125, or 250 Hz. The frequency-dependent effects of vibration on mitochondrial number and generation of oxidative stress were examined. After 10 days of exposure at 125 Hz, ventral tail arteries (VTA) were constricted and there was an increase in mitochondrial number and intensity of ROS staining. In the skin, the influence of vibration on arterioles displayed a similar but insignificant response in VTA. There was also a reduction in the number of small nerves with exposure to vibration at 250 Hz, and a reduction in mitochondrial number in nerves in restrained and all vibrated conditions. There was a significant rise in the size of the sensory receptors with vibration at 125 Hz, and an elevation in ROS levels. Based upon these results, mitochondria number and activity are affected by vibration, especially at frequencies at or near resonance. The influence of vibration on the vascular system may either be adaptive or maladaptive. However, the effects on cutaneous nerves might be a precursor to loss of innervation and sensory function noted in workers exposed to vibration.

Nerve Function Impairment After Acute Vibration Exposure

OBJECTIVE

This study was to investigate the acute effects of hand-arm vibrations on the nerve functions of the hands, and the impact of the grip force applied to the vibrating tool during exposure.

METHODS

Grip strength and perception of vibration, touch, and temperature were evaluated using quantitative sensory testing (QST) before and after vibration exposure in 21 occupationally unexposed individuals. The procedure was performed twice, with a higher grip force being applied during exposure on the second occasion.

RESULTS

Vibration perception was significantly impaired after both exposures. Grip strength, perception of touch, and temperature were only significantly affected after the high grip force exposure.

CONCLUSIONS

Exposure to hand-arm vibrations has acute effects on hand nerve function that are sensitive to the grip force applied during exposure.

Hand-arm Vibration Syndrome in Farmers and its Correlation with Degenerative Triangular Fibrocartilage Complex Injury

Context

Hand-arm vibration syndrome (HAVS) is an occupational disease that affects workers who are exposed to vibrations. Farmers are prone to various musculoskeletal and cumulative trauma disorders. These occur owing to overuse, degeneration, and excess physical efforts along with whole-body vibrations- owing to the use of farming equipment such as tractors and harvesters.

Aims

Aims of the study were to find out the prevalence of various symptoms of HAVS among farmers using tractors, harvesters, etc., and to find out the correlation of triangular fibrocartilage complex (TFCC) injury with HAVS.

Subjects and Methods

A prevalence study was conducted among farmers. Farmers were selected by random sampling method and were asked to fill-up a HAVS surveillance questionnaire. The handgrip strength was recorded with a hand dynamometer. Assessment of carpal tunnel syndrome was done, and correlation of HAVS with TFCC injury was assessed.

Results

Data from 100 farmers was obtained and analyzed. The musculoskeletal symptoms of HAVS, more specifically pain was prevalent (n = 65), followed by sensorineural symptoms (n = 70), and the vascular symptoms were less common (n = 43). HAVS accounts for a prevalence of 64% with 39% of farmers having TFCC injury along with HAVS (P value = <0.0001).

Conclusions

These findings reported in the study provide a better understanding of the impact and extent of HAVS in farmers. There is a significant prevalence of HAVS with mild symptoms of vascular component, mild to moderate symptoms of sensorineural component, and significant involvement of the musculoskeletal component. In addition, TFCC injury is correlated with HAVS.

International consensus criteria for diagnosing and staging hand-arm vibration syndrome

PURPOSE

In the 30 years since the Stockholm Workshop Scale (SWS) was published, the scientific literature on hand-arm vibration syndrome (HAVS) has grown and experience has been gained in its practical application. This research was undertaken to develop an up-to-date evidence-based classification for HAVS by seeking consensus between experts in the field.

METHODS

Seven occupational physicians who are clinically active and have had work published on HAVS in the last 10 years were asked to independently take part in a three-round iterative Delphi process. Consensus was taken when 5/7 (72%) agreed with a particular statement. Experts were asked to provide evidence from the literature or data from their own research to support their views.

RESULTS

Consensus was achieved for most of the questions that were used to develop an updated staging system for HAVS. The vascular and neurological components from the SWS are retained, but ambiguous descriptors and tests without adequately developed methodology such as tactile discrimination, or discriminating power such as grip strength, are not included in the new staging system. A blanching score taken from photographs of the hands during vasospastic episodes is recommended in place of self-recall and frequency of attacks to stage vascular HAVS. Methods with the best evidence base are described for assessing sensory perception and dexterity.

CONCLUSIONS

A new classification has been developed with three stages for the clinical classification of vascular and neurological HAVS based on international consensus. We recommend it replaces the SWS for clinical and research purposes.

Assessment of thermotactile and vibrotactile thresholds for detecting sensorineural components of the hand-arm vibration syndrome (HAVS)

BACKGROUND

Thermotactile thresholds and vibrotactile thresholds are measured to assist the diagnosis of the sensorineural component of the hand-arm vibration syndrome (HAVS).

OBJECTIVES

This study investigates whether thermotactile and vibrotactile thresholds distinguish between fingers with and without numbness and tingling.

METHODS

In 60 males reporting symptoms of the hand-arm vibration syndrome, thermotactile thresholds for detecting hot and cold temperatures and vibrotactile thresholds at 31.5 and 125 Hz were measured on the index and little fingers of both hands.

RESULTS

In fingers reported to suffer numbness or tingling, hot thresholds increased, cold thresholds decreased, and vibrotactile thresholds at both 31.5 and 125 Hz increased. With sensorineural symptoms on all three phalanges (i.e. numbness or tingling scores of 6), both thermotactile thresholds and both vibrotactile thresholds had sensitivities greater than 80% and specificities around 90%, with areas under the receiver operating characteristic curves around 0.9. There were correlations between all four thresholds, but cold thresholds had greater sensitivity and greater specificity on fingers with numbness or tingling on only the distal phalanx (i.e. numbness or tingling scores of 1) suggesting cold thresholds provide better indications of early sensorineural disorder.

CONCLUSIONS

Thermotactile thresholds and vibrotactile thresholds can provide useful indications of sensorineural function in patients reporting symptoms of the sensorineural component of HAVS.

Hand-arm vibration and the risk of vascular and neurological diseases-A systematic review and meta-analysis

Background

Increased occurrence of Raynaud’s phenomenon, neurosensory injury and carpal tunnel syndrome has been reported for more than 100 years in association with work with vibrating machines. The current risk prediction modelling (ISO-5349) for “Raynaud’s phenomenon” is based on a few studies published 70 to 40 years ago. There are no corresponding risk prediction models for neurosensory injury or carpal tunnel syndrome, nor any systematic reviews comprising a statistical synthesis (meta-analysis) of the evidence.

Objectives

Our aim was to provide a systematic review of the literature on the association between Raynaud’s phenomenon, neurosensory injuries and carpal tunnel syndrome and hand-arm vibration (HAV) exposure. Moreover the aim was to estimate the magnitude of such an association using meta-analysis.

Methods

This systematic review covers the scientific literature up to January 2016. The databases used for the literature search were PubMed and Science Direct. We found a total of 4,335 abstracts, which were read and whose validity was assessed according to pre-established criteria. 294 articles were examined in their entirety to determine whether each article met the inclusion criteria. The possible risk of bias was assessed for each article. 52 articles finally met the pre-established criteria for inclusion in the systematic review.

Results

The results show that workers who are exposed to HAV have an increased risk of vascular and neurological diseases compared to non-vibration exposed groups. The crude estimate of the risk increase is approximately 4–5 fold. The estimated effect size (odds ratio) is 6.9 for the studies of Raynaud’s phenomenon when including only the studies judged to have a low risk of bias. The corresponding risk of neurosensory injury is 7.4 and the equivalent of carpal tunnel syndrome is 2.9.

Conclusion

At equal exposures, neurosensory injury occurs with a 3-time factor shorter latency than Raynaud’s phenomenon. Which is why preventive measures should address this vibration health hazard with greater attention.

Tremor and hand-arm vibration syndrome (HAVS) in road maintenance workers

Objectives

The aim of this study was to evaluate postural and rest tremor among workers using vibrating hand tools, taking into account the possible effects of toxicants such as alcohol and tobacco. A further aim was to study workers diagnosed with hand-arm vibration syndrome (HAVS) at the time of examination.

Methods

This study comprises 103 road maintenance workers, 55 exposed to vibrating hand tools (age 41.0 years; range 21–62) and 48 referents (age 38.5 years; range 19–64). They were examined with the CATSYS Tremor Pen^®. Exposure to vibrating tools and serum biomarkers of alcohol and tobacco consumption were measured.

Results

Cumulative exposure to vibrating tools was associated with increased postural (p < 0.01) and rest tremor (p < 0.05) and with a higher Center Frequency of postural tremor (p < 0.01) among smokers and users of smokeless tobacco. Rest tremor Center Frequency was higher than postural tremor frequency (p < 0.001).

Conclusions

The main findings indicate an association between cumulative exposure to hand-held vibrating tools, tremor parameters and consumption of tobacco products. The hand position is important when testing for tremor. Rest tremor had a higher Center Frequency. Postural tremor was more strongly associated with exposure than rest tremor. The finding of increased tremor among the HAVS subjects indicated that tremor might be a part of the clinical picture of a HAVS diagnosis. As with all cross-sectional studies, inferences should be made with caution when drawing conclusions about associations between exposure and possible effects. Future research using longitudinal design is required to validate the findings of the present study.

Long-term daily vibration exposure alters current perception threshold (CPT) sensitivity and myelinated axons in a rat-tail model of vibration-induced injury

Repeated exposure to hand-transmitted vibration through the use of powered hand tools may result in pain and progressive reductions in tactile sensitivity. The goal of the present study was to use an established animal model of vibration-induced injury to characterize changes in sensory nerve function and cellular mechanisms associated with these alterations. Sensory nerve function was assessed weekly using the current perception threshold test and tail-flick analgesia test in male Sprague-Dawley rats exposed to 28 d of tail vibration. After 28 d of exposure, Aβ fiber sensitivity was reduced. This reduction in sensitivity was partly attributed to structural disruption of myelin. In addition, the decrease in sensitivity was also associated with a reduction in myelin basic protein and 2',3'- cyclic nucleotide phosphodiasterase (CNPase) staining in tail nerves, and an increase in circulating calcitonin gene-related peptide (CGRP) concentrations. Changes in Aβ fiber sensitivity and CGRP concentrations may serve as early markers of vibration-induced injury in peripheral nerves. It is conceivable that these markers may be utilized to monitor sensorineural alterations in workers exposed to vibration to potentially prevent additional injury.

Rheumatic effects of vibration at work

Occupational exposures to vibration come in many guises, and they are very common at a population level. It follows that an important minority of working-aged patients seen by medical services will have been exposed to this hazard of employment. Vibration can cause human health effects, which may manifest in the patients that rheumatologists see. In this chapter, we identify the health effects of relevance to them, and review their epidemiology, pathophysiology, clinical presentation, differential diagnosis and vocational and clinical management. On either side of this, we describe the nature and assessment of the hazard, the scale and common patterns of exposure to vibration in the community and the legal basis for controlling health risks, and we comment on the role of health surveillance in detecting early adverse effects and what can be done to prevent the rheumatic effects of vibration at work.

Self-reported cold sensitivity in patients with traumatic hand injuries or hand-arm vibration syndrome - an eight year follow up

BACKGROUND

Cold sensitivity is a common complaint following hand injuries. Our aim was to investigate long-term self-reported cold sensitivity, and its predictors and the importance of sense of coherence (SOC), 8 years after a hand injury as well as in patients treated for Hand Arm Vibration Syndrome (HAVS) during the same time period.

METHODS

Responses to the Cold Intolerance Symptom Severity (CISS) questionnaire and the Sense of Coherence (SOC) questionnaire were investigated in hand injured patients (n = 64) and in patients with HAVS (n = 26). The Mann-Whitney U-Test was used to identify significant differences between subgroups. When analysing predictors for cold sensitivity severity, the Spearman rank correlation (rS coefficient) were used for quantitative predictive variables, Mann-Whitney U-Test for dichotomous variables and Kruskal-Wallis Test for multiple categorical data. The Wilcoxon's signed rank test was used to investigate longitudinal changes in outcome.

RESULTS

There was a significant change in total CISS score for patients with traumatic hand injury, indicating fewer problems with cold sensitivity over time. Symptoms, such as stiffness, weakness and skin colour change on cold exposure, caused fewer problems, but perceived pain/aching and numbness remained unchanged as well as time needed for relief of symptoms on return to a warm environment. The negative impact of cold sensitivity on daily activities and at work was reduced, but problems when engaged in hobbies or when being exposed to cold wintry weather remained unchanged. None of the investigated predictors related to the hand injury were significantly associated with a change in cold sensitivity at the 8-year follow up. In contrast, no significant change in cold sensitivity was noted in the patients with HAVS for any of the situations included in the CISS questionnaire. A lower sense of coherence score correlated significantly with worse cold sensitivity (CISS score) in both patient groups.

CONCLUSIONS

The negative impact of cold sensitivity on daily life was reduced for patients with traumatic hand injury, but did not change over time in patients with HAVS. A low SOC is associated with worse cold sensitivity in such groups of patients. Information about relieving strategies should be provided for patients with cold sensitivity.

Upper limb disability in Norwegian workers with hand-arm vibration syndrome

Background

Hand-arm vibration syndrome (HAVS) is a well-known disease among workers using hand-held vibrating tools. These patients experience major symptoms from their upper limbs. However, there are few studies on disability in this patient group. In this study we wanted to describe the disability of HAVS patients.

Methods

All HAVS patients diagnosed at Haukeland University Hospital in Bergen, Norway in a five-year period were invited. The disabilities of the arm, shoulder and hand (DASH) questionnaire was sent by mail. Clinical data were extracted from their hospital journals. Descriptive statistics and regression analyses were performed.

Results

Thirty-eight patients were recruited. Mean DASH score was 41.2, while the mean of a normal population is 10. Ability to perform tasks related to work and everyday life was affected in these patients. We found a significant association between the DASH score, hand grip strength and tendinitis, also after adjustment for age and smoking in pack-years.

Conclusion

HAVS patients demonstrate a high level of upper limb disability as assessed by the DASH score. Ability to perform tasks related to work and everyday life was affected. We found a significant association between the DASH score, hand grip strength and tendinitis. This should be focused upon in future research.

The effect of hand-arm vibration syndrome on quality of life

BACKGROUND

It is important to determine how hand-arm vibration syndrome (HAVS), a common occupational condition, affects quality of life (QOL).

AIMS

To measure the physical (SF12-P) and mental (SF12-M) components of QOL in workers with HAVS, using the SF12 questionnaire, and to determine the effect of the vascular, sensorineural and musculoskeletal components of HAVS on QOL.

METHODS

Subjects were recruited consecutively from workers with HAVS attending an occupational medicine clinic. They were assessed to determine the Stockholm vascular and sensorineural scale stages as well as an upper extremity pain score, measured by the Borg scale, as an indication of musculoskeletal problems associated with the use of vibrating tools. The SF12-P and SF12-M were both compared with Canadian population normal values after adjusting for age and sex. Multiple linear regression was used to determine the effect of the various HAVS components on SF12-P and SF12-M as well as the effects of age and carpal tunnel syndrome.

RESULTS

One hundred and forty-one subjects were recruited and 139 (99%) agreed to participate, including 134 men and 5 women. The SF12-P and SF12-M scores were significantly below the Canadian population mean values (P < 0.001), indicating lower QOL. In the multiple regression analysis, the predictor with the largest partial R (2) value for both the SF12-P and SF12-M was the upper extremity pain score.

CONCLUSIONS

Both the physical and the mental QOL in workers with HAVS were below Canadian population normal values and subjects' upper extremity pain score had the greatest effect on their QOL.

Normative data for neuromuscular assessment of the hand-arm vibration syndrome and its retrospective applications in Korean male workers

PURPOSE

The purpose of this study was to describe normative data for the neuromuscular assessments of the hand-arm vibration syndrome (HAVS) in Korean.

METHODS

Data for the vibrotactile perception threshold (VPT) at three frequencies (31.5, 125, and 250 Hz), the hand grip strength (HGS), the finger pinch strength (FPS), the finger tapping test, and the Purdue pegboard tests were collected from 120 male office workers aged 30-59 years with no prior history of regular use of handheld vibrating tools. The collected data were compared with the results of a similar study of shipbuilding workers in order to investigate the diagnostic utility of clinical test for HAVS.

RESULTS

The mean VPT values indicate that no significant differences were observed between the dominant and non-dominant hands or between the index and little fingers. The age group of 30s was highly sensitive to vibration input with a peak in sensitivity at 125 Hz among all age groups. In neuromuscular performance, dominant hands are usually more accurate, dexterous, and functionally quicker than non-dominant hands. The index finger was superior to the little finger in the finger tapping counts (p < 0.05). Also, FPS was greater in the index finger than in the middle finger (p < 0.05). The HGS of dominant hands was significantly stronger than that of non-dominant hands (p < 0.05). When the normative data were compared with the data of shipyard workers exposed to vibration, there were statistically significant differences in VPT and neuromuscular functions.

CONCLUSIONS

The current data can be used to evaluate HAVS in Korean male workers. Age is an important factor for VPT.

Hand-arm vibration syndrome: clinical characteristics, conventional electrophysiology and quantitative sensory testing

OBJECTIVE

Workers exposed to vibrating tools may develop hand-arm vibration syndrome (HAVS). We assessed the somatosensory phenotype using quantitative sensory testing (QST) in comparison to electrophysiology to characterize (1) the most sensitive QST parameter for detecting sensory loss, (2) the correlation of QST and electrophysiology, and (3) the frequency of a carpal tunnel syndrome (CTS) in HAVS.

METHODS

QST, cold provocation tests, fine motor skills, and median nerve neurography were used. QST included thermal and mechanical detection and pain thresholds.

RESULTS

Thirty-two patients were examined (54 ± 11 years, 91% men) at the more affected hand compared to 16 matched controls. Vibration detection threshold was the most sensitive parameter to detect sensory loss that was more pronounced in the sensitivity range of Pacinian (150 Hz, x12) than Meissner's corpuscles (20 Hz, x3). QST (84% abnormal) was more sensitive to detect neural dysfunction than conventional electrophysiology (37% abnormal). Motor (34%) and sensory neurography (25%) were abnormal in HAVS. CTS frequency was not increased (9.4%).

CONCLUSION

Findings are consistent with a mechanically-induced, distally pronounced motor and sensory neuropathy independent of CTS.

SIGNIFICANCE

HAVS involves a neuropathy predominantly affecting large fibers with a sensory damage related to resonance frequencies of vibrating tools.

Characterization of frequency-dependent responses of the vascular system to repetitive vibration

OBJECTIVE

Occupational exposure to hand-transmitted vibration can result in damage to nerves and sensory loss. The goal of this study was to assess the frequency-dependent effects of repeated bouts of vibration on sensory nerve function and associated changes in nerves.

METHODS

The tails of rats were exposed to vibration at 62.5, 125, or 250 Hz (constant acceleration of 49 m/s2) for 10 days. The effects on sensory nerve function, nerve morphology, and transcript expression in ventral tail nerves were measured.

RESULTS

Vibration at all frequencies had effects on nerve function and physiology. However, the effects tended to be more prominent with exposure at 250 Hz.

CONCLUSION

Exposure to vibration has detrimental effects on sensory nerve function and physiology. However, many of these changes are more prominent at 250-Hz exposure than at lower frequencies.

DASH work module in workers with hand-arm vibration syndrome

BACKGROUND

The Disabilities of the Arm, Shoulder and Hand work module (DASH-W) questionnaire has not previously been described in relation to hand-arm vibration syndrome (HAVS).

AIMS

To measure work-related disability in workers with HAVS using the DASH-W questionnaire and to determine how the various components of HAVS affect the DASH-W score.

METHODS

Workers with HAVS from a variety of industries were assessed over a 2-year period at the occupational health clinic, St Michael's Hospital, Toronto. Subjects completed the DASH-W questionnaire and were assessed by an occupational physician to determine their Stockholm sensorineural and vascular stages and upper extremity pain score measured by the Borg scale, as an indication of musculoskeletal problems associated with HAVS. The average DASH-W score was compared with the average value for the US population. Multiple linear regression was used to determine the contribution of the various components of HAVS to the DASH-W score.

RESULTS

There were 139 (134 men and 5 women) participants. The subjects with HAVS had a mean DASH-W score of 54.7 (95% CI: 50.3-59.1), which was considerably higher than the average for the US population (P < 0.001). Statistically significant HAVS variables in the multiple linear regression included the Stockholm sensorineural stage (P < 0.05) and the upper extremity pain score (P < 0.001) with the pain score having the highest partial R (2) value.

CONCLUSIONS

Workers with HAVS reported significant upper extremity work-related disability as measured by the DASH-W questionnaire, and the upper extremity pain score made the largest contribution to the DASH-W scores in these subjects.

Exposure assessment in health assessments for hand-arm vibration syndrome

BACKGROUND

Assessing past cumulative vibration exposure is part of assessing the risk of hand-arm vibration syndrome (HAVS) in workers exposed to hand-arm vibration and invariably forms part of a medical assessment of such workers.

AIMS

To investigate the strength of relationships between the presence and severity of HAVS and different cumulative exposure metrics obtained from a self-reporting questionnaire.

METHODS

Cumulative exposure metrics were constructed from a tool-based questionnaire applied in a group of HAVS referrals and workplace field studies. These metrics included simple years of vibration exposure, cumulative total hours of all tool use and differing combinations of acceleration magnitudes for specific tools and their daily use, including the current frequency-weighting method contained in ISO 5349-1:2001.

RESULTS

Use of simple years of exposure is a weak predictor of HAVS or its increasing severity. The calculation of cumulative hours across all vibrating tools used is a more powerful predictor. More complex calculations based on involving likely acceleration data for specific classes of tools, either frequency weighted or not, did not offer a clear further advantage in this dataset. This may be due to the uncertainty associated with workers' recall of their past tool usage or the variability between tools in the magnitude of their vibration emission.

CONCLUSIONS

Assessing years of exposure or 'latency' in a worker should be replaced by cumulative hours of tool use. This can be readily obtained using a tool-pictogram-based self-reporting questionnaire and a simple spreadsheet calculation.

A longitudinal study of peripheral sensory function in vibration-exposed workers

PURPOSE

To investigate prospectively the relation between vibration-induced sensory dysfunction and measures of daily exposure to hand-transmitted vibration (HTV).

METHODS

Thermal perception thresholds for warmth and cold (TPT in °C) and vibrotactile perception thresholds (VPT in dB) at 31.5 and 125 Hz were measured at the fingertips of digit II (for the median nerve) and digit V (for the ulnar nerve) of both hands in 27 male controls and 29 naval engine workers exposed to HTV. In the HTV workers, peripheral sensory function was investigated over a follow-up period of 1-3 years. Vibration exposure was expressed in terms of equivalent frequency-weighted acceleration [A (h(eq,T)) in ms(-2) rms], duration of exposure (T in hours), and frequency-weighted acceleration normalised to a period of 8 h [A(8) in ms(-2) rms].

RESULTS

At baseline, the HTV workers showed significantly higher TPT for warmth and lower TPT for cold than the controls, while no differences in the VPTs at both frequencies were observed between the two groups. After adjustment for several confounders, data analysis with the generalised estimating equations method and a transition model showed that the changes over time in the TPTs of the HTV workers were significantly related to all measures of daily vibration exposure [A (h(eq,T)), T, A(8)]. No significant associations were observed for VPTs at either 31.5 or 125 Hz.

CONCLUSIONS

The findings of this longitudinal study suggest a significant exposure-response relationship between thermal sensory impairment over time and measures of vibration exposure. The measurement of TPT may be a useful testing method to assess vibration-induced neuropathy at an early stage.

Reduced muscle strength in abduction of the index finger: an important clinical sign in hand‐arm vibration syndrome

Muscle strength in extrinsic and intrinsic hand muscle was assessed in 21 patients with hand-arm vibration syndrome. Twenty-one age-matched healthy workers served as controls. Grip and pinch strength was significantly reduced in the vibration-exposed group (18%; p = 0.006 and 18% p = 0.007, respectively) as well as strength of palmar abduction of the thumb (28%; p < 0.0001) and radial abduction of the index finger (37%; p < 0.0001) while abduction strength in the little finger was not significantly reduced (7%). We postulate that the reduced manipulative skill and impaired dexterity of the hand, which often is associated with vibration syndrome, is not only of sensorineural origin but may also be an effect of reduced intrinsic muscle strength. Reduced strength in abduction of the index finger is an important indicator of intrinsic muscular dysfunction in subjects who use hand-held vibrating tools.

Current perception threshold and the HAVS Stockholm sensorineural scale

BACKGROUND

It is important to determine which tests of sensorineural dysfunction identify the neurological damage from hand-arm vibration exposure.

AIMS

To examine the association between the hand-arm vibration syndrome (HAVS) Stockholm sensorineural scale stages and tests of peripheral neurological function including measurement of current perception threshold (CPT) and nerve conduction.

METHODS

All the subjects were men who were assessed for HAVS with a medical and occupational history and physical examination to determine the Stockholm stage, CPT testing at frequencies of 5, 250 and 2000 Hz for the median and ulnar nerves and measurement of nerve conduction carried out in a blinded fashion.

RESULTS

A total of 155 of the 157 recruited subjects agreed to take part in the study, a 99% participation rate. CPT was statistically significantly increased (P < 0.001) in both Stockholm sensorineural Stages 1 and > or =2 in comparison to Stage 0 for every frequency and nerve combination. However, CPT could not discriminate well between Stages 1 and > or =2. There was no association between median or ulnar neuropathy measured by nerve conduction and the Stockholm stages. Polychotomous multinomial logistic regression indicated that the CPT measurements at 2000 Hz, corresponding to damage to large myelinated nerve fibres, were most predictive of both Stockholm Stages 1 and > or =2 in comparison to Stage 0.

CONCLUSIONS

Neuropathy measured by nerve conduction was unrelated to the Stockholm scale stages. CPT was increased above Stage 0 but did not distinguish well between the higher stages of the Stockholm scale.

Upper extremity disability in workers with hand-arm vibration syndrome

BACKGROUND

Hand-arm vibration syndrome (HAVS) is a common occupational problem and it is important to understand the disability associated with this condition.

AIMS

To measure upper extremity disability using the disabilities of the arm, shoulder and hand (DASH) questionnaire in workers with HAVS and to determine how this disability is affected by the vascular and neurological components of HAVS and other factors, in particular musculoskeletal variables.

METHODS

Subjects were recruited from HAVS patients assessed at St Michael's Hospital, Toronto, Canada, over a 2-year period. All participants were assessed by an occupational medicine specialist to determine the specific components of HAVS and musculoskeletal variables including upper extremity pain score measured by the Borg scale. The DASH questionnaire was completed on the same day as the clinical assessment and before any feedback had been given about the clinical findings.

RESULTS

A total of 141 workers with HAVS were recruited and 139 agreed to participate in the study. This study group had a statistically significantly higher mean DASH score than the US population (P < 0.001). The multiple linear regression analysis indicated that upper extremity pain score (P < 0.001), the Stockholm sensorineural scale (P < 0.01) and the number of fingers blanching (P < 0.05) had a statistically significant association with an increase in the DASH score. The highest partial R(2) value was for the upper extremity pain score.

CONCLUSIONS

Workers with HAVS have significant upper extremity disability and musculoskeletal factors appear to make an important contribution to this disability.

Syndromes from segmental vibration and nerve entrapment: observations on case definitions for carpal tunnel syndrome

OBJECTIVES

The purpose of this paper is to assess the overlap and stability of two different case definitions of carpal tunnel syndrome CTS. The analysis considers the association between different case definitions and objective tests (sensory nerve conduction velocities, SNCVs and vibrotactile perception thresholds, TTS), and the natural history of CTS, in the context of two vibration-exposed cohorts.

METHODS

Clinical CTS cases were defined in two ways: (1) by the study physician using fixed criteria, and; (2) by questionnaire and hand diagram. SNCV in median and ulnar nerves was measured for digital, transpalmar, and transcarpal segments, and conventionally as from wrist-digit. Skin temperature was assessed as a point measurement by thermistor and regionally by thermal imaging. VTTs were determined at the bilateral fingertips of the third and fifth digits using a tactometer meeting the requirements of ISO 13091-1 (ISO 2001). The subjects were cohorts of shipyard workers in 2001 and 2004, and dental hygienists in 2002 and 2004.

RESULTS

Results are reported for 214 shipyard workers in 2001 and 135 in 2004, and for 94 dental hygienists in 2002 and 66 in 2004. In 2001, 50% of shipyard workers were diagnosed as CTS cases by at least one of the diagnostic schemes, but only 20% were positive by both criteria. Among study physician diagnosed cases, 64% were CTS negative in 2001, 76% were negative in 2004, 13% were positive in both years, 22% became negative after being positive, and 11% became positive after being negative. For only study physician diagnosed CTS did VTTs differ between cases differ and non-cases in digit 3; there was no such distinction in digit 5. The dental hygienists had little CTS.

CONCLUSION

Clinical case definitions of CTS based on diagrams and self-assessment, and clinical evaluation have limited overlap. Combining clinical criteria to create a more narrow or specific case definition of CTS does not appear to predict SNCV. The natural history of CTS suggests a protean disorder with considerable flux in case status over time.

Negligent exposures to hand-transmitted vibration

OBJECTIVES

If the negligence of an employer results in the disability in an employee, the employer is responsible, in whole or in part, for the disability. The employer is wholly responsible when the worker would not have developed the disability if the employer had taken all reasonable preventative measures. The employer is only partly responsible if the worker would probably have developed some disability even if the employer had taken all reasonable precautions. The employer's responsibility may be estimated from the difference between the actual disability of the worker and the disability that the worker would have suffered if the employer had taken all reasonable preventative measures. This paper considers alternative ways of apportioning negligent and non-negligent exposures to hand-transmitted vibration.

RESULTS

The equivalent daily vibration exposure, A(8), used in current EU Directives is shown to be unsuitable for distinguishing between the consequences of negligent and non-negligent exposures because the risks of developing a disorder from hand-transmitted vibration also depend on the years of exposure. Furthermore, daily exposures take no account of individual susceptibility or the practicality of reducing exposure. The consequences of employer negligence may be estimated from the delay in the onset and progression of disorder that would have been achieved if the employer had acted reasonably, such as by reducing vibration magnitude and exposure duration to the minimum that was reasonably achievable in the circumstances. This seems to be fair and reasonable for both employers and employees and indicates the consequences of negligence-the period of the worker's life with disease as a result of negligence and the period for which their employment opportunities may be restricted as a result of the onset of the disorder due to negligence.

CONCLUSIONS

The effects of negligence may be estimated from the delay in the onset of disease or disability that would have occurred if the employer had behaved reasonably. This definition of negligence encourages employers to reduce risks to the lowest reasonably practical level, consistent with EU Directives.

Measurement, evaluation, and assessment of peripheral neurological disorders caused by hand-transmitted vibration

Regular exposure to hand-transmitted vibration can result in symptoms and signs of peripheral vascular, neurological and other disorders collectively known as the hand-arm vibration syndrome. The measurement of the effects of hand-transmitted vibration involves converting the evidence of disorder (symptoms and signs) into information that can be stored. Evaluation requires the use of scales on which to indicate the severity of the various symptoms and signs. Assessment involves a judgement of severity relative to a criterion, usually for a specific purpose (e.g. to decide on removal from work or compensation). The measurement and evaluation of symptoms and signs is necessary when monitoring patient health and when performing epidemiological studies for research. The assessment of the severity of the hand-arm vibration syndrome is currently performed with staging systems, but the criteria are not clear and not related to defined methods for measuring or evaluating the symptoms and signs. Recognizing that similar symptoms can occur without injury from occupational exposures to hand-transmitted vibration, this paper attempts to define significant peripheral neurological symptoms caused by hand-transmitted vibration (i.e. 'unusual symptoms') and how these symptoms and related signs may be measured. Scales for evaluating the symptoms (e.g. their extent) and the related signs (e.g. their probability relative to the probability of the sign being present in persons not exposed to vibration) are defined. A method of relating unusual symptoms to both the signs of disorder and the pattern of vibration exposure is illustrated. Assessments of severity will vary according to the reasons for assessing the health effects of vibration, and will depend on local practice and convenience, but a way of combining evaluations of symptoms and signs is demonstrated in a staging system. Although inherently complex, the methods may assist the collection of data required to improve understanding of the effects of hand-transmitted vibration and also support a more complete reporting of the condition in those adversely affected by hand-transmitted vibration.

Grading of sensorineural disturbances according to a modified Stockholm workshop scale using self-reports and QST

OBJECTIVE

The objective of the study was to apply, on a group of vibration exposed individuals, a proposed modification of the Stockholm Workshop scale for grading of sensorineural disorders by using self-reports and data from objective testing and to compare grading obtained through the two approaches.

METHODS

The study group consisted of 126 young persons with different individual levels of hand-transmitted vibration exposures. Effect measurements included a self-administered questionnaire and vibrotactile perception measurements and Purdue Pegboard testing. For grading using self reports three specific questions, believed to be good markers for complaints of intermittent numbness, sensory deficiency, and reduced performance in fine motor tasks, was picked out from the questionnaire. Results from vibrotactile perception and Purdue Pegboard testing were used for grading based on quantitative sensory testing. The sensorineural grading obtained by the two methods was then compared.

RESULTS

The outcome showed that about 60% of all individuals within the study group are graded equally by the two methods for grading. The frequency of individuals graded at advanced SN stages were however higher when using QST, predominantly due to more positive cases for the Purdue pegboard test compared with the corresponding outcome from the self reports.

CONCLUSION

The proposed modification of the grading scale reduces the in-built progressiveness and allows different combinations of sensorineural symptoms. The two grading methods seem to be somewhat correlated, something which may be considered as encouraging and promising for those who prefer to use, or must use one of the methods for grading. The proposed model for grading using self-reports should, however, be considered more as a conceptual idea for how this may be done. The models should be applied on a larger, more vibration exposed and more symptomatic study group, compared with the present study group, before any far-reaching conclusions can be drawn.

A prospective cohort study of manipulative dexterity in vibration-exposed workers

OBJECTIVES

To investigate the relation between manipulative dexterity and vibration exposure, ergonomic risk factors, and upper limb disorders in a group of workers exposed to hand-transmitted vibration (HTV).

METHODS

Manipulative dexterity was investigated on 115 HTV workers (82 forestry workers and 33 stone workers) and 64 control men over 1-year follow-up period. The Purdue pegboard method was used to test manipulative dexterity which was scored for the dominant hand, non-dominant hand, and both hands. Information about individual, work and health history was obtained by means of a standardised questionnaire. Vibration exposure was assessed in terms of tool vibration magnitudes, daily and total exposure duration, and cumulative vibration dose.

RESULTS

On the cross-sectional investigation, Purdue pegboard scores were significantly lower in the HTV workers than in the controls (0.001 < P < 0.05). Over 1-year follow-up period, Purdue pegboard scores were found to be inversely related to age, smoking and use of vibratory tools (0.001 < P < 0.05). Moreover, deterioration of some measures of manipulative dexterity was significantly associated with sensorineural and vascular symptoms in the fingers of the HTV workers. Random-intercept linear regression analysis showed that Purdue pegboard scores decreased with the increase of vibration exposure. The reduction of assembly score (i.e. number of pins, collars, and washers assembled in a 60-s period) was significantly associated with the increase in vibration exposure and ergonomic stress (neck-upper arm posture, hand-intensive work, and total ergonomic score). Purdue pegboard scores tended to improve over the follow-up period in both the controls and the HTV workers, suggesting a possible learning effect over time.

CONCLUSION

The findings of this longitudinal study suggest an association between deterioration of manipulative dexterity and neurovascular symptoms in the fingers of HTV workers. There was evidence for a significant relation between loss of precise manipulation and exposures to hand-transmitted vibration and ergonomic risk factors.

Relationship between self-reported upper limb disability and quantitative tests in hand-arm vibration syndrome

PURPOSE

To establish the relationship between quantitative tests of hand function and upper limb disability, as measured by the Disability of the Arm, Shoulder and Hand (DASH) questionnaire, in hand-arm vibration syndrome (HAVS).

METHOD

A total of 228 individuals with HAVS were included in this study. Each had undergone a full HAVS assessment by an experienced physician, including quantitative tests of vibrotactile and thermal perception thresholds, maximal hand-grip strength (HG) and the Purdue pegboard (PP) test. Individuals were also asked to complete a DASH questionnaire.

RESULTS

PP and HG of the quantitative tests gave the best and statistically significant individual correlations with the DASH disability score (r2 = 0.168 and 0.096). Stepwise linear regression analysis revealed that only PP and HG measurements were statistically significant predictors of upper limb disability (r2 = 0.178). Overall a combination of the PP and HG measurements, rather than each alone, gave slightly better discrimination, although not statistically significant, between normal and abnormal DASH scores with a sensitivity of 73.1% and specificity of 64.3%.

CONCLUSIONS

Measurements of manual dexterity and hand-grip strength using PP and HG may be useful in helping to confirm lack of upper limb function and 'perceived' disability in HAVS.

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.

Quality of life in Swedish workers exposed to hand–arm vibration

The objective of the present study was to analyse whether differences existed among workers exposed to hand-arm vibration (HAV) with regard to quality of life (QoL) issues. One hundred and eight male workers from a heavy manufacturing plant, with and without HAV symptoms, and workers referred to a hand surgery department with severe HAV symptoms participated in the study. The participants attended a clinical interview, were given a physical examination of the hands and administered the Göteborg Quality of Life instrument and the Evaluation of Daily Activity Questionnaire (EDAQ). Results indicated that workers referred to a hand surgery department with more severe HAV symptoms described a lower quality of life, defined here as lower subjective well-being, more symptoms of ill-health and difficulties with activities of daily living (ADL), than workers with no HAV symptoms. Workers from a heavy manufacturing plant with HAV symptoms experienced more difficulties with ADL, especially while working outdoors in cold weather, than workers with no HAV symptoms. Limitations of the present study include the use of a subjective scale to describe HAV symptoms. Further research is recommended on a larger sample of workers at risk for HAV symptoms to develop preventative ergonomic strategies.

Sensory nerve conduction velocities of median, ulnar and radial nerves in patients with vibration syndrome

OBJECTIVE

The present study aimed to clarify the range of involvement for hand-arm vibration syndrome (VS) in the median, ulnar and radial nerves of the hand.

METHODS

Sensory nerve conduction velocities (SCVs) for 3 nerves in the hands and arms were examined for 34 patients with VS and 23 age-matched controls. Neuropathy types were classified by possible carpal tunnel syndrome (CTS), Guyon's syndrome and digital neuropathy in three nerves.

RESULTS

SCV in the median nerve (middle finger, wrist-elbow) and ulnar nerve (little finger, wrist-elbow), and amplitudes of the median nerve (wrist-proximal and distal parts of the middle finger), ulnar nerve (wrist-proximal and distal parts of the little finger; forearm-proximal part of the little finger; upper arm-proximal part of the little finger) and radial nerve (dorsal side of the hand-thumb) were significantly reduced in VS patients compared with controls. According to subject classifications based on the results of SCV and amplitude of nerve action potential, 52.9% of VS patients displayed multi-focal neuropathy including digital neuropathy, possible CTS and/or Guyon's syndrome.

CONCLUSION

These findings suggest that VS affects all three nerves in the hand. According to classification results, the main disorders of peripheral nerves comprise digital neuropathy.

Nerve conduction and sensorineural function in dental hygienists using high frequency ultrasound handpieces

BACKGROUND

Oscillatory vibration from industrial power tools poses a well-recognized risk of peripheral nerve injury. There have been reports of elevated vibrotactile perception thresholds (VPT) among dentists, dental technicians, and dental hygienists, using rotary devices and ultrasonics. Elevated VPTs are an indicator of small fiber nerve or mechanoreceptor injury, but the high frequencies associated with dental instruments are presumed by the ISO to exceed physiological response upper thresholds. This study examines nerve conduction and sensorineural deficits in dental hygienists.

METHODS

A cross-sectional study of 94 experienced dental hygienists was conducted to assess peripheral nerve function and clinical signs and symptoms. Specialized testing included measurement of VPTs for three different categories of mechanoreceptors, sensory nerve conduction tests with fractionated digit and palmar segments, and measurement of calibrated pinch force with force sensitive resistors (FSRs) during a simulated procedure.

RESULTS

Chronic hand paresthesias were described by 44.7% of experienced dental hygienists. Sensory nerve conduction velocity (SNCV) across the wrist-palm segment of the median nerve. VPTs were particularly elevated at the FAII mechanoreceptor among experienced dental hygienists. Compared to participants without carpal tunnel syndrome (CTS), as defined by study criteria, 14 experienced hygienists with diagnosed CTS had almost twice the average weekly use of vibratory instruments -8.3 hr versus 4.5 hr, and had SNCV deficits along the digit -47.11 m/sec (+8.70) versus 42.57 m/sec (+8.25), and across the wrist -44.04 m/sec (+7.15) versus 41.36 m/sec (+9.27). There was a distinct subset of dental hygienists (27%) with a combination of low calibrated pinch force in simulations, subjective loss of strength and elevated VPTs, especially in the FAII mechanoreceptor population -110.82 db (+8.57) versus 104.84 db (+6.80) in the rest of the cohort. This subset also had a higher prevalence of paresthesias (67% vs. 39%) and greater cumulative vibration exposure (OR = 1.206 [CI 1.005-1.448]), than other hygienists.

CONCLUSIONS

The high levels of paresthesias observed among dental hygienists appear to be attributable to several pathophysiological mechanisms, including, sensory nerve demyelination at the carpal tunnel and intrinsic to the digits, and dysfunction of fingertip mechanoreceptors. A distinct sub-population appears to exhibit a high level of accumulated abnormality.