Vibration-induced White Finger Research Articles

Rheological and immunological findings in dockers with vibration-induced white fingers.

The aim of the present study was to characterize rheological and immunological features involved in the pathogenesis of vibration-induced white fingers (VWF). Plasma viscosity, at two shear rates (580 s-1 and 1164 s-1), levels of immunoglobulins (IgG, IgM, IgA), circulating immune complexes, rheumatoid factor, antinuclear antibodies, fibronectin, fibrinogen, hemoglobin and erythrocyte sedimentation rate were analysed in 30 male dockers with VWF and in 30 healthy male referents unexposed for hand-arm vibrations. Decreased plasma viscosity was observed among the men with VWF, although formal significance (P less than 0.05) was only obtained at shear rate 580 s-1. The decrease was mainly seen among smokers. In the study there were no significant differences between the VWF group and the referents with regard to immunoglobulin levels, autoantibodies and other plasma proteins. From the study it is concluded that workers with VWF may have a decreased plasma viscosity. The biological relevance of this observation is uncertain and deserves further study.

Hand-arm vibration syndrome and its prevalence in the present status of private forestry enterprises in Japan.

Currently there are no limitations on age of employment on private forestries in Japan. Hence, it was hypothesized that in these kind of enterprises, elderly chain saw operators, or those with long-term exposure, might be at higher risk of developing hand-arm vibration syndrome (HAVS). We consequently investigated the prevalence of HAVS in 447 chain saw workers on private forestries in Gifu Prefecture, Japan, with particular reference to age and exposure period. Of this population, 43 (9.6%) had signs and symptoms of vibration-induced white finger (VWF), and among these workers the severity of finger blanching was significantly correlated (P less than 0.01) with the exposure period. Classification of all subjects by exposure period showed that workers with greater than or equal to 30 years' exposure had higher prevalences of VWF (20.9%) and numbness of the hands (25.4%) compared to other groups. Significant differences (P less than 0.01) were found between the functional capacities of workers with VWF and those of control subjects. We concluded that (a) the elderly chain saw operators and those with longer exposure should be moved to other jobs with a lower or no risk of exposure to vibration, and (b) the results of screening tests, even without cold water immersion (which we did not employ, in order to protect workers' hands), could be helpful for the identification of workers with VWF.

Hand-Arm Vibration Isolation Materials: A Range of Performance Evaluation

Abstract Compliant materials used as a surface treatment for power tool handles may provide reductions in acceleration levels transmitted to the hand. With continued use of some power tools, operators experience symptoms of hand-arm vibration syndrome, vibration-induced white finger, and carpal tunnel syndrome. The numbing and tingling sensation experienced by tool operators has become known as a precursor to more advanced stages of hand-arm vibration syndrome and vibration-induced white finger and is being linked to carpal tunnel syndrome. This study measures the acceleration levels on a bar, vibrating handle attached to a vibration exciter, as well as the acceleration at the surface of a contacting hand. A comparison is made of the changes in vibration levels measured from the same handle covered with various materials. Results are reported in the form of acceleration transmissibility in one-third octave format, which represents isolation effectiveness. Using two grip strengths, 100 and 25 N, an extende...

Sympathetic nerve activity in the skin in relation to vibration-induced white finger.

With a microneurographic method, sympathetic nerve activity in the skin was recorded from median nerve fascicles of six patients with vibration-induced white finger and four age- and gender-matched normal subjects. At an ambient temperature of 15 degrees C the sympathetic nerve activity was greater in the patients than in the normal subjects. The burst activity was increased in all of the subjects during the water immersion test of the contralateral hand, but neither the increase in the mean burst number nor the mean area under the neurogram showed statistically significant group differences. Thus, although vasoconstrictive tone is greater in patients with vibration-induced white finger than in healthy subjects, no support could be found for the hypothesis that increased vascular tone is of prime importance for attacks of white finger in vibration-exposed subjects.

Combined effects of noise and hand-arm vibration on auditory organ and peripheral circulation

This paper first presents an overview of an epidemiological study on noise-induced hearing loss (NIHL) in relation to vibration-induced white finger (VWF). Secondly, the results obtained in a model experiment with a chain-saw under laboratory conditions are discussed from the viewpoints of elucidating the etiological mechanisms of VWF and NIHL. In the epidemiological study, in which 499 chain-saw workers were examined, chain-saw workers with VWF showed a significantly greater hearing loss at high frequencies than those without VWF. Next, an experimental study was designed to determine whether a combination of noise and vibration produced more pronounced changes in temporary shifts of finger skin temperature and temporary threshold shift (TTS) of hearing than those resulting from exposure to either stress alone. The results suggested that noise might play a part in inducing the constriction of the peripheral vessels seen with local exposure to vibration, and that hand-arm vibration may produce an additive effect on the noise-induced TTS. Furthermore, finger skin temperature and finger blood flow were measured simultaneously as indicators of peripheral circulatory movement for five healthy subjects. The relation between the synergistic action of noise and vibration and the participation of the sympathetic nervous system are also discussed.

Activation of blood coagulation and fibrinolysis in vibration syndrome

The pathophysiology of peripheral circulatory disturbance in patients presenting with vibration syndrome was studied from the viewpoint of blood coagulation. Plasma levels of fibronectin (FN), vitronectin (VN), thrombin-antithrombin III complex (TAT), and alpha 2-plasmin inhibitor-plasmin complex (PIC) were measured in 23 subjects who showed no evidence of vibration-induced white finger [VWF(-) group] and in 24 patients who presented with VWF [VWF(+) group]. In the VWF(-) group, plasma FN concentrations were elevated but plasma TAT and PIC levels were within the normal ranges. In the VWF(+) group, plasma FN concentrations were normal but plasma TAT and PIC levels were significantly elevated. In both groups, plasma VN concentrations were similar to those in normal controls. For purposes of comparison, 32 patients presenting with diabetes mellitus were also studied. They were divided into 2 groups, 13 subjects who showed no evidence of angiopathy [complication(-) group] and 19 patients who presented with angiopathy [complication(+) group]. In the complication(+) group, plasma TAT and PIC concentrations were significantly elevated, as in the VWF(+) group. These results suggest that in vibration syndrome, vibration, cold stimulus, or other factors first injure the vascular endothelium, resulting in a rise in plasma FN, and that in the VWF(+) group, augmentation of coagulation and fibrinolysis induces a state of compensated disseminated intravascular coagulation (DIC).

Finger blood pressure and rewarming rate for screening and diagnosis of Raynaud's phenomenon in workers exposed to vibration.

Both the finger systolic blood pressure (FSP) and the rewarming test of finger skin are measures of circulation in the finger; the first reflects the vasoconstriction phase and the second the vasodilatation phase. The combinations of the specificity and the sensitivity of these methods were evaluated by a receiver operating characteristic curve (ROC). The material included 37 vibration-induced white finger (VWF) cases, five primary Raynaud's cases, and 37 controls. The specificity of the FSP test was high with regard to the anamnesis of white finger and the test was useful for the diagnosis of Raynaud's phenomenon, but the sensitivity was too low for screening. The rewarming test was useful for screening primary Raynaud's case and possibly for screening disorders in peripheral vasodilative function. The connections between the rewarming test and VWF are not clear and according to the present study the rewarming test was not suitable for screening VWF.

Autonomic and peripheral nervous system dysfunction in workers exposed to hand-arm vibration: a study of R-R interval variability and distribution of nerve conduction velocities.

To assess the effects of vibrating-tool operation on the autonomic and peripheral nervous system, we measured the variability in the electrocardiographic R-R interval (CVRR) and the distribution of nerve conduction velocities (DCV) in 24 men who were vibrating-tool operators and in 17 healthy adult men (control group). Of the 24 tool operators, 13 had a history of vibration-induced white finger [VWF(+) group] and 11 had no such history [VWF(-) group]. Two components of CVRR, i.e. C-CVRSA and C-CVMWSA, which have been considered to reflect parasympathetic and sympathetic activities, respectively, were also examined. Both the CVRR and the C-CVRSA in the VWF(+) group and the CVRR in the VWF(-) group were found to be significantly depressed as compared with the control values; moreover, a significant difference in the C-CVRSA was observed between the VWF(+) group and the VWF(-) group. The faster DCVs and the sensory median nerve conduction velocity were significantly slowed in the VWF(+) and VWF(-) groups. The C-CVMWSA was significantly correlated with most of the DCV parameters and with the median nerve conduction velocities in all 24 vibrating-tool operators. These data suggest that operation of vibrating tools, which involves exposure to combined stressors of local vibration, heavy work, climate, and noise, affects both the faster myelinated nerve-fiber activity and the parasympathetic activity; the sympathetic activity at rest in workers exposed to hand-arm vibration may be related to depression of peripheral nerve conduction.

Circulatory disturbances of the foot in vibration syndrome

Circulatory disturbances of the foot in patients with vibration syndrome were studied by measuring the skin temperature of both index fingers and great toes through a 3-min immersion of the right foot in cold water at 10 degrees C. Subjects included 11 patients with vibration-induced white finger (VWF) [VWF(+) group], 12 patients without VWF [VWF(-) group], and 20 healthy referents not exposed to vibration. Patients were all male chain saw operators who had scarcely been exposed to vibration of the foot. The prevalence of coldness felt in the upper and lower extremities was greater than 90% in the VWF(+) group, about 60% in the VWF(-) group, and less than 10% in the referents. The extent of the coldness was greatest in the VWF(+) group. The skin temperature of both fingers and toes was lowest in the VWF(+) group, somewhat higher in the VWF(-) group, and highest in the referents both before and after immersion. These findings indicate that patients with vibration syndrome, especially those with VWF, have circulatory disturbances in the foot as well as in the hand. The disturbances in the foot may be related to long-term repeated vasoconstriction in the foot induced by hand-arm vibration through the sympathetic nervous system.

Diagnostic value of finger systolic blood pressure in the assessment of vasospastic reactions in the finger skin of vibration-exposed subjects after finger and body cooling.

To assess the severity of vibration-induced white finger (VWF), finger systolic blood pressure (FSBP) after finger cooling and after combined finger and body cooling was measured by strain-guage plethysmography for 100 vibration-exposed men and 22 healthy men. The exposed men were classified as being without VWF (EW), with mild VWF (EM), and with severe VWF (ES) according to records of blanching attacks. FSBP was significantly reduced only in the ES group after finger cooling and in the ES and EM groups after both body and finger cooling. The diagnostic sensitivity and specificity for VWF was 81.7 and 90.3%, respectively. Skin temperature measurements before and after immersion in cold water (5 degrees C, for 10 min) could not be used for the estimation of VWF severity.

EXPOSURE TO VIBRATION AND SELF-REPORTED HEALTH COMPLAINTS OF RIVETERS IN THE AIRCRAFT INDUSTRY<xref ref-type="fn" rid="fn1"><sup>*</sup></xref>

Workers using vibrating tools may experience neurological and vascular symptoms in the fingers and hands. The effect of vibration exposure on bone and joint disorders in the hand, arm and shoulder is less clear. In a cross-sectional study, riveters and controls in an aircraft company were investigated for vibration exposure and health complaints. Vibration measurements showed that frequency-weighted acceleration levels for riveting hammers and bucking bars ranged from 5.5 to 12.3 m s -2. The calculated equivalent frequency-weighted acceleration for a period of 4 h was the questionnaire survey 101 riveters reported statistically significant more complaints of pain and stiffness in their hands and arms when compared with 76 controls with no, or little, exposure to vibration. After 10 years of exposure statistically significant age-adjusted odds ratios (P less than 0.05) were found for vibration-induced white finger (VWF) (1.9) and pain or stiffness of the wrist (3.2). Although they were not statistically significant (0.05 less than P less than 0.10) odds ratios appreciably greater than 1 were found for numbness in fingers (1.6) and pain or stiffness in the elbow (1.6) and the shoulder (1.5), and these complaints were strongly associated with duration of exposure to vibration. With logistic regression the probabilities for a riveter of having symptoms of VWF after 10 and 20 years of exposure was estimated to be P = 0.18 and P = 0.29, respectively, which can be compared with the prevalences predicted by the dose-response relationship for VWF in ISO 5349, which are 10 and 30%. The results of this study suggest that exposure to vibration from working with impact power tools can contribute to complaints of pain and stiffness in the hand, arm and shoulder, and especially in the wrist.

Comparing subjective and objective assessments of the severity of vibration induced white finger

The present staging of the disease severity of vibration induced white finger (VWF) is based on the patients' symptoms. Forty patients, with a history of VWF, with disease severity stage III or stage IV, on the Taylor-Pelmear scale, were investigated. Total, reactive hyperaemic blood flow to the hands was measured using an isotope limb blood flow (ILBF) technique. Skin blood flow patterns were assessed using a cold provocation test, followed by thermographic assessment of hand rewarming. Thermographic abnormalities were detected in 39 patients (97%). Decreased post-occlusive, reactive hyperaemic blood flow occurred in 29 patients (73%). There was no difference in skin blood flow patterns or in total hand blood flow between the stage III and stage IV groups. Reduction of postocclusive reactive hyperaemic blood flow may be indicative of occlusive lesions of the digital vessels. We conclude that the classification of the severity of VWF using subjective assessment, needs to be augmented by objective evidence of altered blood flow.

Altered sensitivity of digital blood flow to acute vibration in patients with vasospastic disease

Fifteen patients with primary Raynaud's, 18 patients with vibration induced white finger (VWF) and 15 controls were exposed to sine wave vibration, with an amplitude of 0.15 mm and frequencies of 40, 80 and 120 Hz. Baseline digital blood flow was measured using venous occlusion strain gauge plethysmography. A digit was vibrated for 1 min and subsequent blood flow measurements were taken from both vibrated and non-vibrated digits. Vibration at 40 Hz causes a significant decrease in flow in the vibrated digits of the control group only ( P < 0.05, Wilcoxon test). Vibration at 80 Hz shows a significant decrease in blood flow in the vibrated digits of both the control and the VWF groups ( P < 0.005) and also in the non-vibrated digits of the VWF group ( P < 0.05). Vibration at 120 Hz significantly decreases blood flow in the vibrated digits of control, VWF and Raynauds groups ( P < 0.001). The Raynaud's non-vibrated digits also had decreased flow ( P < 0.005). These results imply that patients with established vasospastic disease are less sensitive to the direct effects of acute vibration than controls. The results also imply that vibration at 40, 80 and 120 Hz affect digital blood flow in controls through local mechanism. Vibration at certain frequencies, appears to modulate blood flow in patients with vasospastic disease by acting through central mechanisms.

Response to cold and abnormalities of nerve conduction velocity in hand-arm vibration syndrome.

The hand-arm vibration syndrome (HAVS) contains both vascular (vibration induced white finger (VIWF)) and sensorineural components. Although a close link between the two has been found in some studies,1 others indicate that vasomotor and neuropathic dysfunction develop independently.2 We have found support for the second view while comparing the results of a cold provocation test with electrophysiological nerve conduction velocity (NCV) studies.

Vibration Exposure, Vibration-Induced White Finger and Digital Arterial Tone in Chain Saw Operators

In a group of 65 Italian forestry operators using chain saws, the overall prevalence of vibration-induced white finger (VWF) was found to be 29.2%. The occurrence of VWF was higher in the chain sawyers who had operated non-antivibration (non-A/V) as well as A/V saws (46.4%) than in those with experience limited to A/V saws (16.2%). The latency time before VWF averaged 9.4 yr (SD 6.8). The mean value of the four-hour energy-equivalent frequency-weighted acceleration [(ah,w)eq(4)] was 7.2 m/s2 (SD 1.2). On the basis of the known VWF prevalence and of [(ah,w)eq(4)], a latent period before VWF of 7.1 yr was expected according to ISO 5349. The measurement of finger systolic pressure (FSP) at 15°C and 10°C by plethysmographic technique showed that the chain sawyers affected with VWF experienced a more intense digital vasospasm than a group of comparable controls and the chain sawyers without VWF. The sensitivity of the method to detect vibration-induced digital arterial hyper-responsiveness to cold was 84.2% and the specificity was 100%. The findings of this study showed a good agreement between the expected and observed latency times before VWF, even though the ISO dose-effect relationship seems to overestimate slightly the risk. The results of the cold test indicated that the measurement of FSP during local cooling is an accurate laboratory method to diagnose objectively Raynaud's phenomenon of occupational origin.

An improved biomechanical model for simulating the strain of the hand-arm system under vibration stress

In order to define relationships between the vibration stress and the strain of the human hand-arm system a biomechanical model was developed. The four masses of the model representing the hand, the forearm and the upper arm were connected by dampers and springs in two perpendicular directions. Simulating muscle activity, damped torsion springs were included additionally. The motions of the model were described by a differential matrix equation which was solved by using a ‘transfer matrix routine’ as well as by numerical integration. Thus, functions with harmonic or transient time courses could be selected as an excitation. The simulated vibrations were compared with those of other hand-arm models. The forces and torques transmitted between the masses, and the energy dissipated by the dampers were computed for several combinations of exciter frequencies and accelerations. The dependence of torques upon excitation agreed fairly well with the behaviour of the arm muscles under vibration as described by various investigators. At frequencies above 100 Hz the energy was dissipated mainly by the dampers between the masses near to the exciter. Transferring this result to the hand-arm system it shows that at high frequencies energy is dissipated by the hand and its palmar tissues and this might be one cause for the incidence of vibration-induced white finger disease.

Vibration perception threshold of forest worker's finger during temporary obstructed blood circulation

Vibration detection threshold (VPT) of 149 professional forest workers was measured during a compulsory annual health examination. The authors' earlier developed measuring method for VPT of finger was modified. The blood circulation of the hand was obstructed for 6 min and VPT was measured 4 min after releasing the obstruction. VPTs of all forest workers increased during obstruction. In forest workers suffering from decreased hand grip force (decreased HGF) the increase of VPT differed significantly from forest workers without symptoms, and VPT in the former group still increased after releasing the obstruction. VPT remained also at the raised level after releasing the obstruction with forest workers suffering from vibration-induced white finger (VWF). Nevertheless, on an individual basis even the modified measuring method failed to discriminate subjects without symptoms from those with symptoms of hand-arm vibration syndrome. The raised VPT and sensitivity for obstruction of blood circulation suggest that the reason for decreased HGF in forest workers may be a consequence of an injury in the peripheral nerves.

Physiological reactions during brush saw operation

An experimental study of the physiological effects of brush saw operation was performed on eight professional agricultural workers. The experiments were carried out in the field under practical working conditions. Aesthesiometric thresholds (two-point discrimination and depth sense perception), manipulative dexterity, pinch grip force and fingertip skin temperature (FST) were measured before and after exposure to different combinations of static load (handle holding), noise and vibration by using new production brush saws for 5 to 15 min. The changes in the peripheral circulatory, sensorineural and muscular functions of the brush saw workers were not found to be significantly different under the various exposure conditions. Static load accounted for the major part of the changes in aesthesiometric thresholds, pinch grip force and FST after brush saw operation. With respect to baseline measurements, no significant difference in manipulative skill was observed after each exposure period. The weighted vibration accelerations from the right and left handles of a brush saw were 3.13 and 1.80 m/s2, respectively. The assessment of brush saw vibration exposure according to ISO 5349 and the results of FST measurements were consistent with the findings of some epidemiological surveys indicating a low risk of vibration-induced white finger among brush sawyers. This investigation pointed out that the increase in the aesthesiometric thresholds was mainly determined by handle holding, and that the reduction in gripping force during actual work was related to the duration of brush saw operation. Therefore, prolonged static overload on the nerves, muscles and joints of the hand-arm system could explain the increased risk of musculoskeletal and sensorineural disorders found among brush saw users.

Medical aspects of the hand-arm vibration syndrome

A review of the effects of hand-arm vibration on workers using hand-held vibrating tools is presented. Epidemiological, clinical and physiological investigations indicate that hand-arm vibration can provoke digital vasospastic symptoms (vibration-induced white finger), peripheral sensorineural disturbances (finger numbness, impaired tactile function) and musculoskeletal abnormalities in the hands and arms (muscle fatigue, degenerative changes in bones and joints). The complex of peripheral neurological, circulatory and musculoskeletal lesions occurring in vibration-exposed workers is called “Hand-Arm Vibration Syndrome”. It is believed that different mechanisms are involved in the etiopathogenesis of vibration-induced disorders in the upper limbs and, consequently, the symptoms may develop independently though concurrently. At present, the neurological and vascular components of the hand-arm vibration syndrome are classified separately according to two staging systems proposed at an international symposium held in Stockholm in 1986. It is generally accepted that chronic disturbances of the central nervous system, such as insomnia, vertigo, headache, etc., should not be included in the hand-arm vibration syndrome. The relationship between exposure to segmental vibration and changes in autonomic tone is still uncertain and requires further research.

Physical Characteristics of Vibration in Relation to Vibration-Induced White Finger

Predicted and observed prevalences and latency periods of vibration-induced white finger (VWF) were examined among workers exposed to hand-arm vibration. The different physical characteristics of vibration--spectra and impulsiveness--were measured. The following groups of workers were included in the study: forest workers (n = 199), pedestal grinders (n = 12), stone workers (n = 16), shipyard workers (n = 171), and platers (n = 5). The exposure to vibration was measured according to the ISO 5349 method. The impulsiveness of vibration was defined as the difference between peak levels and RMS levels. A good agreement was observed between the predicted and observed data for prevalence and latency of VWF in the forest workers. For the tools with high impulsiveness used in grinding, stone works, and shipyard assembly hall, the results were nonconfirmative; and there was a poor correlation between vibration and VWF. The ISO 5349 standard does not consider the high peak values of the vibration signal which may comprise high-frequency components and cause short transients in the underlying tissue of the worker's hand. These characteristics in vibration may be hazardous in the genesis of VWF and cannot be predicted when measuring vibration by the present standard method.