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

Evaluation of the bio-dynamic response of the hand-arm system and hand-tool designs - A brief review

Hand-operated tools transmit a high magnitude of vibration exposure to the hand-arm system that causes occupational diseases. The health effects caused in various countries for the past years due to usage of hand tools are necessary to identify the occupational disorders. Researchers have conducted various studies on biological effects, hand-transmitted vibration exposure and biodynamic responses throughout the years. This article goes over each of these studies in detail, as well as identifying areas where more research is needed. The majority of studies deal with the following topics: general guidelines for hand-transmitted vibrations; assessment techniques of vibration exposure; hand-tool evaluation methods; influence of hand-tool design to overcome the biomechanical effects; and finite element modelling for quantifying vibration exposure. In response to this, understanding the biodynamic behaviour of the hand-arm system is useful for better ergonomic intervention in hand tools to reduce fatigue and increase comfort.

Vibration Exposure Safety Guidelines for Surgeons Using Power-Assisted Liposuction (PAL)

BACKGROUND

As power-assisted liposuction (PAL) gains in popularity, plastic surgeons operating these devices experience occupational exposure to hand-transmitted vibration, which can result in hand-arm vibration syndrome, a debilitating neurovasculopathy.

OBJECTIVES

The objective of the study was to determine vibration exposure from the utilization of a PAL device during surgery to generate recommendations for safe use.

METHODS

Vibration emission of a commonly utilized PAL system (MicroAire-650, Surgical Instruments, Charlottesville, VA) was examined employing a vibration data logger under both controlled laboratory conditions and during 13 typical liposuction cases. Data were analyzed and compared with established safety limits of vibration exposure.

RESULTS

The experiments demonstrated a mean vibration magnitude of typical liposuction surgeries to be 5.69 ± 0.77 m/s2 (range, 4.59-6.27 m/s2), which is significantly higher than the manufacturer declared value of 3.77 m/s2. Cannula size was shown to be the most significant contributor to vibration magnitude, with larger cannulas causing more vibration transmission.

CONCLUSIONS

These results indicate that recommendations must be made to prevent undue occupational exposure to vibration from PAL. The MicroAire-650 can generally be safely utilized for less than 1.5 h/d. At exposure levels >1.5 h/d, there is increased risk of developing vibration-related injuries, and vibration-reducing strategies should be implemented. At exposure levels >6 h/d, the safety limit is exceeded and there is significantly increased risk of developing hand-arm vibration syndrome and vibration exposure should be halted.

LEVEL OF EVIDENCE: 4

Dose-response relationship between hand-arm vibration exposure and vibrotactile thresholds among roadworkers

BACKGROUND

Testing of vibration perception threshold (VPT) at the fingertips as a quantitative measure of tactile sensitivity is a commonly used tool in diagnosing hand-arm vibration syndrome. There is limited research on dose-response relationships between hand-arm vibration (HAV) exposure and VPT on an individual level.

AIMS

Assess possible dose-response relationships on an individual level between HAV exposure and VPT at the fingertips.

METHODS

We assessed average daily vibration exposure (m/s²A8) and cumulative lifetime HAV exposure for 104 participants from different departments in a road maintenance company based on vibration measurements and questionnaires. VPT was measured based on the technical method described in ISO 13091-1:2005 using octave frequencies 8-500 Hz. We investigated associations using linear regression models with significance level p≤0.05.

RESULTS

The participants were either exposed to rock drills (n=33), impact wrenches (n=52) or none of these tools (n=19). Exposure to rock drills and impact wrenches was associated with elevated VPT for all seven test frequencies in the second and fifth fingers of both hands. A dose-response with the daily exposure measure m/s²(A8) was found based on 1.2 m/s²(A8) for impact wrenches, and 5.4 m/s²(A8) for rock drills. A stronger association was found with the cumulative exposure for rock drills compared with impact wrenches, and for the second finger compared with the fifth finger.

CONCLUSIONS

HAV exposure was associated with elevated VPT, also at exposure levels below the common exposure action value of 2.5 m/s²(A8). Lowering the HAV exposure can contribute to prevent increasing VPTs in these workers.

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.

Long-term effect of hand-arm vibration on thermotactile perception thresholds

Background

Occupational exposure to hand-transmitted vibration (HTV) is known to cause neurological symptoms such as numbness, reduced manual dexterity, grip strength and sensory perception. The purpose of this longitudinal study was to compare thermotactile perception thresholds for cold (TPT_C) and warmth (TPT_W) among vibration exposed manual workers and unexposed white collar workers during a follow-up period of 16 years to elucidate if long-term vibration exposure is related to a change in TPT over time.

Methods

The study group consisted of male workers at a production workshop at which some of them were exposed to HTV. They were investigated in 1992 and followed-up in 2008. All participants were physically examined and performed TPT bilaterally at the middle and distal phalanges of the second finger. Two different vibration exposure dosages were calculated for each individual, i.e. the individual cumulative lifetime dose (mh/s²) or a lifetime 8-h equivalent daily exposure (m/s²).

Results

A significant mean threshold difference was found for all subjects of about 4-5 °C and 1-2 °C in TPT_W and TPT_C, respectively, between follow-up and baseline. No significant mean difference in TPT_C between vibration exposed and non-exposed workers at each occasion could be stated to exist. For TPT_W a small but significant difference was found for the right index finger only. Age was strongly related to thermotactile perception threshold. The 8-h equivalent exposure level (A (8)) dropped from about 1.3 m/s² in 1992 to about 0.7 m/s² in 2008.

Conclusions

A lifetime 8-h equivalent daily exposure to hand-transmitted vibration less than 1.3 m/s² does not have a significant effect on thermotactile perception. Age, however, has a significant impact on the change of temperature perception thresholds why this covariate has to be considered when using TPT as a tool for health screening.

Health effects associated with occupational exposure to hand-arm or whole body vibration

Workers in a number of different occupational sectors are exposed to workplace vibration on a daily basis. This exposure may arise through the use of powered-hand tools or hand-transmitted vibration (HTV). Workers might also be exposed to whole body vibration (WBV) by driving delivery vehicles, earth moving equipment, or through use of tools that generate vibration at low dominant frequencies and high amplitudes, such as jackhammers. Occupational exposure to vibration has been associated with an increased risk of musculoskeletal pain in the back, neck, hands, shoulders, and hips. Occupational exposure may also contribute to the development of peripheral and cardiovascular disorders and gastrointestinal problems. In addition, there are more recent data suggesting that occupational exposure to vibration may enhance the risk of developing certain cancers. The aim of this review is to provide an assessment of the occupations where exposure to vibration is most prevalent, and a description of the adverse health effects associated with occupational exposure to vibration. This review will examine (1) various experimental methods used to measure and describe the characteristics of vibration generated by various tools and vehicles, (2) the etiology of vibration-induced disorders, and (3) how these data were employed to assess and improve intervention strategies and equipment that reduces the transmission of vibration to the body. Finally, there is a discussion of the research gaps that need to be investigated to further reduction in the incidence of vibration-induced illnesses and injuries.

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.

Thermal perception thresholds among workers in a cold climate

Purpose

To investigate whether exposure to cold could influence the thermal perception thresholds in a working population.

Methods

This cross-sectional study was comprised of 251 males and females and was carried out at two mines in the northern part of Norway and Sweden. The testing included a baseline questionnaire, a clinical examination and measurements of thermal perception thresholds, on both hands, the index (Digit 2) and little (Digit 5) fingers, for heat and cold.

Results

The thermal perception thresholds were affected by age, gender and test site. The thresholds were impaired by experiences of frostbite in the fingers and the use of medication that potentially could affect neurosensory functions. No differences were found between the calculated normative values for these workers and those in other comparative investigations conducted in warmer climates.

Conclusions

The study provided no support for the hypothesis that living and working in cold climate will lead to impaired thermal perception thresholds. Exposure to cold that had caused localized damage in the form of frostbite was shown to lead to impaired thermal perception.

Whole-body vibration and musculoskeletal diseases in professional truck drivers

Abstract Background: Most occupational diseases do not fit the paradigm of medical interpretation of the health-disease process based on linear causality, in which it would be possible to find a single cause for each type of disease. Objectives: to conduct a systematic review in order to investigate the association between whole-body vibration (WBV) and musculoskeletal disorders (MSD) in professional truck drivers (PTD). Methods: The scientific databases of PubMed, Cochrane, Lilacs and Scielo were used to collect articles published from 2000 until the present time. Two independent reviewers adopted inclusion and quality criteria to evaluate the selected articles. Results: From adopted inclusion and quality criteria, nine articles were chosen to identify the association between MSD and WBV in PTD. The results showed that MSD seems to be closely associated to exposure to WBV in these workers, mainly due to high prevalence and symptoms of low back pain. Two cohort studies showed exposure to WBV as risk for MSD. Only one, with case-control design, did not show WBV as a significant factor. Conclusions: In this study the importance of exposure analysis of WBV in the occurrence of MSD in PTD was elucidated. This study showed the importance of WBV exposure analysis on the occurrence of MSD in PTD. There is adequate information to provide rationale for the reduction of WBV exposure to the lowest possible level, to ensure the health of these workers. Studies with a greater power of investigation, of a prospective, design, should be encouraged, supplanting those only of association.

Quantitative neurosensory findings, symptoms and signs in young vibration exposed workers

Background

Long-term exposure to hand-held vibrating tools may cause the hand arm vibration syndrome (HAVS) including vibration induced white fingers and sensorineural symptoms. The aim was to study early neurosensory effects by quantitative vibrotactile and monofilament tests in young workers with hand-held vibration exposure.

Methods

This cross-sectional study consisted of 142 young, male machine shop and construction workers with hand-held exposure to vibrating tools. They were compared with 41 non-vibration exposed subjects of the same age-group. All participants passed a structured interview, answered several questionnaires and had a physical examination including the determination of vibrotactile perception thresholds (VPTs) at two frequencies (31.5 and 125 Hz) and Semmes Weinstein’s Monofilament test.

Results

In the vibration exposed group 8% of the workers reported episodes of tingling sensations and 10% numbness in their fingers. Approximately 5–10% of the exposed population displayed abnormal results on monofilament tests. The vibrotactile testing showed significantly increased VPTs for 125 Hz in dig II bilaterally (right hand, p = 0.01; left hand, p = 0.024) in the vibration exposed group.

A multiple regression analysis (VPT - dependent variable; age, height, examiner and five different vibration dose calculations – predictor variables) in dig II bilaterally showed rather low R²-values. None of the explanatory variables including five separately calculated vibration doses were included in the models, neither for the total vibration exposed group, nor for the highest exposed quartile.

A logistic multiple regression analysis (result of monofilament testing - dependent variable; age, height, examiner and five vibration dose calculations – predictor variables) of the results of monofilament testing in dig II bilaterally gave a similar outcome. None of the independent variables including five calculated vibration doses were included in the models neither for the total exposed group nor for the highest exposed quartile.

Conclusion

In spite of the fairly short vibration exposure, a tendency to raised VPTs as well as pathologic monofilament test results was observed. Thus, early neurophysiologic symptoms and signs of vibration exposure may appear after short-term exposure also in young workers.