Pathophysiology and classification of the vibration white finger

Thrombosed Persistent Median Artery with Coexisting Bifid Median Nerve in a Robotic Arthroplasty Surgeon: A Case Report

CASE

A 47-year-old orthopaedic surgeon presented with acute volar left wrist pain. He performed over 250 robot-assisted knee arthroplasties each year. Color Doppler evaluation revealed bilateral persistent median arteries and bifid median nerves, with focal occlusive thrombosis of the left median artery. He was advised rest and oral aspirin. He could return to his professional activities after 1 month. He had no recurrence of symptoms at 1 year of follow-up.

CONCLUSION

Orthopaedic surgeons use vibrating hand tools on a daily basis. The possibility of hand-arm vibration syndrome must be considered in the differential diagnosis of wrist pain among orthopaedic surgeons.

The effects of standing foot-transmitted vibration on self-reported discomfort ratings

BACKGROUND

Occupational foot-transmitted vibration (FTV) exposure is common in industries like mining, construction, and agriculture, often leading to acute and chronic injuries. Vibration assessments require technical expertise and equipment which can be costly for employers to perform. Alternatively, researchers have observed that self-reported discomfort can be used as an effective indicator of injury risk.

OBJECTIVE

This study aimed to investigate the effect of standing FTV exposure on self-reported ratings of discomfort, and whether these subjective ratings differed by body area and exposure frequency.

METHODS

Participants (n = 30) were randomly exposed to standing FTV at six frequencies (25, 30, 35, 40, 45, and 50 Hz) for 20-45 seconds. Following each exposure, participants rated discomfort on a scale of 0-9 in four body areas: head and neck (HN), upper body (UB), lower body (LB), and total body.

RESULTS

Results indicated that participants experienced the most discomfort in the LB at higher frequencies (p < 0.001), consistent with the resonance of foot structures. The HN discomfort tended to decrease as the exposure frequency increased, although not statistically significant (p > 0.0167). The UB discomfort remained relatively low across all frequencies.

CONCLUSIONS

The study suggests a potential connection between resonant frequencies and discomfort, potentially indicating injury risk. Although self-reported discomfort is insufficient for directly assessing injury risk from FTV, it provides a simple method for monitoring potential musculoskeletal risks related to vibration exposure at resonant frequencies. While professional vibration assessment remains necessary, self-reported discomfort may act as an early indicated of vibration-induced injuries, aiding in implementing mitigation strategies.

Effects on blood parameters from hand-arm vibrations exposure

Vibration exposure from handheld tools can affect the hands with neurological symptoms and vibration-induced Raynaud's phenomenon (VRP). The underlying pathophysiological mechanisms are not fully known, however, changes in the composition of blood parameters may contribute to VRP with an increase in blood viscosity and inflammatory response. The aim of this study was to examine the effect on blood parameters in capillary blood from fingers that had been exposed to a vibrating hand-held tool. This study involved nine healthy participants who had been exposed to vibration and an unexposed control group of six participants. Capillary blood samples were collected before and after vibration exposure for the exposed group, and repeated samples also from the control group. The exposed groups were exposed to vibration for a 15-min period or until they reached a 5.0 m/s² vibration dose. Analysis of blood status and differential counting of leucocytes was performed on the capillary blood samples. The results of the blood samples showed an increase in mean value for erythrocyte volume fraction (EVF), hemoglobin, red blood cell count, white blood cell count and neutrophils, as well as a decrease of mean cell volume, mean cell hemoglobin, and mean cell hemoglobin concentration. The increase of EVF and neutrophils was statistically significant for samples taken from the index finger but not the little finger. Even though the study was small it showed that an acute vibration exposure to the hands might increase EVF and neutrophilic granulocytes levels in the capillary blood taken from index fingers.

Exposure to Hand-Arm Vibration in the Australian Workforce

OBJECTIVE

To estimate the prevalence of hand-arm vibration (HAV) in Australian workplaces.

METHODS

The Australian Workplace Exposure Survey (AWES)-Hearing was a cross-sectional telephone survey of Australian workers conducted in 2016-2017. Respondents were asked about the time spent using tools or performing tasks known to be associated with HAV during their most recent working day. We created a library of HAV magnitude levels for each tool/task and estimated each worker's daily HAV exposure level using standard formulae. We categorized each worker as to whether they exceeded the daily occupational limits of 2.5 and 5.0 m/s2. Results were extrapolated to the Australian working population using a raked weighting method.

RESULTS

In our sample of 4991 workers, 5.4% of men and 0.7% of women exceeded the HAV action limit of 2.5 m/s2 on their most recent working day. We estimate that 3.8% of the Australian workforce exceeds the HAV limit of 2.5 m/s2 and 0.8% exceeds the 5 m/s2 limit. Men were more likely to exceed the HAV limits than women, as were those with trade qualifications, and those who worked in remote locations. Workers in the construction, farming, and automobile industries had the highest prevalence of HAV exposure. Tool groups that contributed to higher exposure levels included: compactors, rollers, and tampers; power hammers and jackhammers; and underground mining equipment.

CONCLUSIONS

HAV is common in the Australian working population. Given the health risks associated with this exposure, reduction strategies and interventions should be developed, with engineering controls as the starting point for exposure reduction strategies.

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: A rarely seen diagnosis

Hand-arm vibration syndrome (HAVS) is a collection of sensory, vascular, and musculoskeletal symptoms caused by repetitive trauma from vibration. This case report demonstrates how to diagnose HAVS on the basis of history, physical examination, and vascular imaging and its treatment options. A 41-year-old man who regularly used vibrating tools presented with nonhealing wounds on his right thumb and third digit. Arteriography revealed occlusions of multiple arteries in his hand with formation of collaterals. We diagnosed HAVS, and his wounds healed after several weeks with appropriate treatment. HAVS is a debilitating condition with often irreversible vascular damage, requiring early diagnosis and treatment.

Plexin-D1/Semaphorin 3E pathway may contribute to dysregulation of vascular tone control and defective angiogenesis in systemic sclerosis

Introduction

The vascular and nervous systems have several anatomic and molecular mechanism similarities. Emerging evidence suggests that proteins involved in transmitting axonal guidance cues, including members of class III semaphorin (Sema3) family, play a critical role in blood vessel guidance during physiological and pathological vascular development. Sema3E is a natural antiangiogenic molecule that causes filopodial retraction in endothelial cells, inhibiting cell adhesion by disrupting integrin-mediated adhesive structures. The aim of the present study was to investigate whether in systemic sclerosis (SSc) Plexin-D1/Sema3E axis could be involved in the dysregulation of vascular tone control and angiogenesis.

Methods

Sema3E levels were measured by quantitative colorimetric sandwich ELISA in serum samples from 48 SSc patients, 45 subjects with primary Raynaud's phenomenon (pRP) and 48 age-matched and sex-matched healthy controls. Immunofluorescence staining on skin sections from 14 SSc patients and 12 healthy subjects was performed to evaluate Sema3E and Plexin-D1 expression. Western blotting was used to assess Plexin-D1/Sema3E axis in human SSc and healthy dermal microvascular endothelial cells (SSc-MVECs and H-MVECs, respectively) at basal condition and after stimulation with recombinant human vascular endothelial growth factor (VEGF), SSc and healthy sera. Capillary morphogenesis on Matrigel was performed on H-MVECs treated with healthy, pRP or SSc sera in the presence of Sema3E and Plexin-D1 soluble peptides.

Results

Serum Sema3E levels were significantly higher both in pRP subjects and SSc patients than in controls. In SSc, Sema3E levels were significantly increased in patients with early nailfold videocapillaroscopy (NVC) pattern compared to active/late patterns and pRP, and in patients without digital ulcers versus those with ulcers. In SSc skin, Sema3E expression was strongly increased in the microvascular endothelium. Cultured SSc-MVECs showed higher levels of phosphorylated Plexin-D1 and Sema3E expression than H-MVECs, and stimulation with SSc sera increased phosphorylated Plexin-D1 and Sema3E in H-MVECs. The addition of Sema3E-binding Plexin-D1 soluble peptide significantly attenuated the antiangiogenic effect of SSc sera on H-MVECs.

Conclusions

Our findings suggest that Plexin-D1/Sema3E axis is triggered in SSc endothelium and may have a role in the dysregulation of angiogenesis and vascular tone control by inducing neuro-vascular mechanism alterations clinically evident in particular in the early disease phases.

Vibration induced white-feet: overview and field study of vibration exposure and reported symptoms in workers

BACKGROUND

Workers who stand on platforms or equipment that vibrate are exposed to foot-transmitted vibration (FTV). Exposure to FTV can lead to vibration white feet/toes resulting in blanching of the toes, and tingling and numbness in the feet and toes.

OBJECTIVES

The objectives are 1) to review the current state of knowledge of the health risks associated with foot-transmitted vibration (FTV), and 2) to identify the characteristics of FTV and discuss the associated risk of vibration-induced injury.

PARTICIPANTS

Workers who operated locomotives (n=3), bolting platforms (n=10), jumbo drills (n=7), raise drilling platforms (n=4), and crushers (n=3), participated.

METHODS

A tri-axial accelerometer was used to measure FTV in accordance with ISO 2631-1 guidelines. Frequency-weighted root-mean-square acceleration and the dominant frequency are reported. Participants were also asked to report pain/ache/discomfort in the hands and/or feet.

RESULTS

Reports of pain/discomfort/ache were highest in raise platform workers and jumbo drill operators who were exposed to FTV in the 40 Hz and 28 Hz range respectively. Reports of discomfort/ache/pain were lowest in the locomotive and crusher operators who were exposed to FTV below 10 Hz. These findings are consistent with animal studies that have shown vascular and neural damage in exposed appendages occurs at frequencies above 40 Hz.

CONCLUSIONS

Operators exposed to FTV at 40 Hz appear to be at greater risk of experiencing vibration induced injury. Future research is required to document the characteristics of FTV and epidemiological evidence is required to link exposure with injury.

Whole body vibration at different exposure frequencies: infrared thermography and physiological effects

The aim of this study was to investigate the effects of whole body vibration (WBV) on physiological parameters, cutaneous temperature, tactile sensitivity, and balance. Twenty-four healthy adults (25.3 ± 2.6 years) participated in four WBV sessions. They spent 15 minutes on a vibration platform in the vertical mode at four different frequencies (31, 35, 40, and 44 Hz) with 1 mm of amplitude. All variables were measured before and after WBV exposure. Pressure sensation in five anatomical regions and both feet was determined using Von Frey monofilaments. Postural sway was measured using a force plate. Cutaneous temperature was obtained with an infrared camera. WBV influences the discharge of the skin touch-pressure receptors, decreasing sensitivity at all measured frequencies and foot regions (P ≤ 0.05). Regarding balance, no differences were found after 20 minutes of WBV at frequencies of 31 and 35 Hz. At 40 and 44 Hz, participants showed higher anterior-posterior center of pressure (COP) velocity and length. The cutaneous temperature of the lower limbs decreased during and 10 minutes after WBV. WBV decreases touch-pressure sensitivity at all measured frequencies 10 min after exposure. This may be related to the impaired balance at higher frequencies since these variables have a role in maintaining postural stability. Vasoconstriction might explain the decreased lower limb temperature.

Raynaud's phenomenon: from molecular pathogenesis to therapy

Raynaud's phenomenon (RP) is a well defined clinical syndrome characterized by recurrent episodes of digital vasospasm triggered by exposure to physical/chemical or emotional stress. RP has been classified as primary or secondary, depending on whether it occurs as an isolated condition (pRP) or is associated to an underlying disease, mainly a connective tissue disease (CTD-RP). In both cases, it manifests with unique "triple" (pallor, cyanosis and erythema), or "double" color changes. pRP is usually a benign condition, while sRP can evolve and be complicated by acral digital ulcers and gangrene, which may require surgical treatment. The pathogenesis of RP has not yet been entirely clarified, nor is it known whether autoantibodies have a role in RP. Even so, recent advances in our understanding of the pathophysiology have highlighted novel potential therapeutic targets. The aim of this review is to discuss the etiology, epidemiology, risk factors, clinical manifestations, recently disclosed pathogenic mechanisms underlying RP and their correlation with the available therapeutic options, focusing primarily on pRP and CTD-RP.

A comparison of hand-arm vibration syndrome between Malaysian and Japanese workers

OBJECTIVES

The aim of this study was to investigate the clinical characteristics of HAVS in a tropical environment in comparison with a temperate environment.

METHODS

We conducted a series medical examinations among the forestry, construction and automobile industry workers in Malaysia adopting the compulsory medical examination procedure used by Wakayama Medical University for Japanese vibratory tools workers. We matched the duration of vibration exposure and compared our results against the Japanese workers. We also compared the results of the Malaysian tree fellers against a group of symptomatic Japanese tree fellers diagnosed with HAVS.

RESULTS

Malaysian subjects reported a similar prevalence of finger tingling, numbness and dullness (Malaysian=25.0%, Japanese=21.5%, p=0.444) but had a lower finger skin temperature (FST) and higher vibrotactile perception threshold (VPT) values as compared with the Japanese workers. No white finger was reported in Malaysian subjects. The FST and VPT of the Malaysian tree fellers were at least as bad as the Japanese tree fellers despite a shorter duration (mean difference=20.12 years, 95%CI=14.50, 25.40) of vibration exposure.

CONCLUSIONS

Although the vascular disorder does not manifest clinically in the tropical environment, the severity of HAVS can be as bad as in the temperate environment with predominantly neurological disorder. Hence, it is essential to formulate national legislation for the control of the occupational vibration exposure.

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.

Noise-induced hearing loss in construction workers being assessed for hand-arm vibration syndrome

BACKGROUND

Construction workers are at risk of noise-induced hearing loss (NIHL) but often have no periodic audiometric testing.

METHODS

The participants were construction workers assessed for Hand-Arm Vibration Syndrome (HAVS) at the Occupational Health Clinic, St. Michael's Hospital, Toronto, Ontario. Audiometry was offered and 169 of the 191 workers assessed for HAVS agreed to have the audiometric test. The objective was to examine the prevalence of hearing loss in these 169 workers and to determine the effect on hearing of duration of work in construction (as a proxy for noise exposure) and the severity of vibration white finger (VWF) which previous studies have suggested is a marker for increased individual susceptibility for NIHL. VWF was measured by the Stockholm vascular scale.

RESULTS

All participants were men, median age of 57 (range: 28-75), median number of years worked in construction of 35 (range: 4-52). All of the Spearman rank correlations between years worked in construction and the hearing levels at each audiometric frequency were statistically significant (p < 0.001). Overall, 31 (18.3%) participants had hearing loss at or above the level at which a workers' compensation pension would be granted in Ontario and the prevalence of this auditory outcome had a statistically significant increase as years worked in construction increased. Multivariate linear regression indicated that VWF also had a statistically significant effect on hearing loss for all audiometric frequencies combined after controlling for years worked in construction.

CONCLUSION

Improved prevention of hearing loss in construction workers is needed.

Occupational changes in manual tactile sensibility of the dentist

The aim of this study was to find out if the use of vibrating tools (drill, ultrasonic scaler ...) in dental practice has negative side effects on the manual tactile sensibility of the dentist. The sensory tests were performed on 50 subjects, who were allocated to three different groups according to their occupation and the length of their working experience. The first test group consisted of 20 dentists, who had more than 25 years of work experience. As a control group, 20 non-dentists were recruited to obtain a similar age distribution as the former test group. A final group consisted of 10 dentists with more than 1 year of work experience. All subjects underwent three tests: light-touch sensation test, two-point discrimination test and thermal sensation test on the thumb and the index finger of the working and non-working hands. Results showed significant differences, especially for the light-touch sensation test. The study showed more specifically that the tactile sensibility of the working hand of the dentists with more than 25 years of work experience was significantly diminished with respect to the non-working hand and to the working hand of non-dentists. In the test group of young dentists, there was no noticeable reduction of manual tactile sensibility.

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.

Assessing the Influence of Antivibration Glove on Digital Vascular Responses to Acute Hand‐arm Vibration

This study was designed to assess the influence of an antivibration glove on digital vascular responses in healthy subjects exposed to short-term grasping of a vibrating handle. To measure finger blood flow (FBF) and finger skin temperature (FST) once at the end of every min, a blood flowmeter sensor was attached to the dorsum and a thermistor sensor was attached to the medial surface of the subject's middle phalanx of the third finger of the right hand. After 5 min of baseline measurements without or with an antivibration glove meeting ISO standard 10819, worn on the right hand, subjects gripped a vibrating handle with the same hand for a period of 5 min. Vibration was generated at two frequencies of 31.5 Hz and 250 Hz with a frequency weighted rms acceleration of 5.5 m/s(2). FBF and FST continued to be recorded for a further 5 min after release of the vibrating handle. Statistical analysis showed no significant change after vibration exposure in either FST or FBF at 250 Hz, compared to baseline (control) measurements while using the antivibration glove. At 31.5 Hz, FBF data exhibited a significant difference between before and after grasping of vibrating handle, which was less under the condition of wearing the antivibration glove than under the condition of bare hand. The results provide evidence that the antivibration glove considerably influenced finger vascular changes in healthy subjects induced by vibration exposure, especially against high frequency vibration. Further studies are required to assess finger vascular responses to hand-transmitted vibration with antivibration gloves of different manufacturers.

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.

Hand–arm vibration syndrome with concomitant arterial thrombosis in the hands

BACKGROUND

Hand-arm vibration syndrome (HAVS) refers to the vascular, neurological and musculoskeletal effects that may occur in workers with prolonged exposure to vibrating tools. Hypothenar hammer syndrome (HHS) is a lesion of the ulnar artery at the level of the hamate bone secondary to single or repeated episodes of trauma to the hypothenar eminence. The literature suggests that digital arterial thrombosis and HHS may be associated with the use of vibrating tools.

AIM

This study will familiarize investigators with the range of vascular abnormalities seen in workers using vibrating tools, and highlight the importance of screening for arterial thrombosis in the hand when assessing hand-arm vibration-exposed patients.

METHODS

In the patients referred to our clinic for HAVS assessment, three were identified during the period 2001 to 2004 who had vascular occlusions in the hands in addition to HAVS. In addition to standardized HAVS vascular investigations, all three patients had arteriograms based on a significantly positive Allen's test.

RESULTS

All three cases had documented HAVS based on vascular testing. Arteriograms revealed a spectrum of severity of arterial thromboses from severe HHS, to occlusion limited to the digital arteries.

CONCLUSION

Our study reports three cases of HAVS with concomitant HHS and/or digital artery thrombosis. These findings support previous reports of an association between HAVS and vascular thrombosis in the hands. Screening for arterial occlusive problems in the hands should be included in the HAVS work up.

Potential occupational health problems for dentists in Flanders, Belgium

The aim of this study was to gather data on occupational health effects among Flemish dentists. A questionnaire on various potential health effects was sent out to randomly selected Flemish dentists. Pilot experimental studies were performed on hearing and sensory function of the fingers on small groups of dentists. Audiometric data of both ears, gathered with an interval of 10 years, were analysed. Sensory tests of the fingers were performed for dominant and non-dominant hands in relation to exposure time to (ultra)sonic equipment. Positive responses for the questionnaire were as follows: low back pain, 54% (stress-correlated); vision problems, 52.3% (age-correlated); infections, 9%; allergies, 22.5% (mainly latex); stress level was scored 7 on a scale from 0 to 10; diminished sensitivity of the fingertips, 6% and auditory disorders, 19.6%. Pilot audiometric data showed a hearing loss at 4,000 Hz for the left ear, presumably indicative of occupational noise trauma. The two-point discrimination ability of the dominant hand tended to diminish in line with the number of years of practice. Dentists in Flanders were found to suffer from various health-related problems. More elaborate studies are required to provide more details on the risks for occupational hearing impairment and vibration hand neuropathy and to determine whether the problems described were related to the practice of dentistry.

Evidence for frequency-dependent arterial damage in vibrated rat tails

The effects of single 4-hr bouts of continuous 30, 60, 120, and 800 Hz tail vibration (49 m/sec2, root mean squared) were compared to assess frequency-amplitude-related structural damage of the ventral caudal artery. Amplitudes were 3.9, 0.98, 0.24, and 0.0055 mm, respectively. Vibrated, sham-vibrated, and normal arteries were processed for light and electron microscopy. The Curry rat tail model of hand-arm vibration (Curry et al. Muscle Nerve 2002;25:527-534) proved well-suited for testing multiple frequencies. NFATc3 immunostaining, an early marker of cell damage, increased in smooth muscle and endothelial cells after 30, 60, and 120 Hz but not 800 Hz. Increased vacuolization, which is indicative of smooth muscle contraction, occurred for all frequencies except 800 Hz. Vacuoles increased in both endothelial and smooth muscle cells after 60 and 120 Hz. Only 30 Hz showed pronounced smooth muscle cell vacuolization along the internal and external elastic membranes, suggesting stretch-mediated contraction from the large amplitude shear stress. Discontinuities in toluidine blue staining of the internal elastic membrane (IEM) increased for all frequencies, indicating vibration-induced structural weakening of this structure. Patches of missing IEM and overlying endothelium occurred in approximately 5% of arteries after 60, 120, and 800 Hz. The pattern of damage after 800 Hz suggests that the IEM is disrupted because it resonates at this frequency. Vibration acceleration stress and smooth muscle contraction appear to be the major contributors to arterial damage. The pattern of vibration-induced arterial damage of smooth muscle and endothelial cells is frequency-amplitude-dependent.

Thermoregulation and rheological properties of blood in primary Raynaud?s phenomenon and the vibration-induced white-finger syndrome

OBJECTIVE

Frequent use of vibrating tools may lead to typical attacks of Raynaud's phenomenon (RP). The present study assesses the feasibility of the use of thermographic measurements of blood rheometry in the diagnosis of vibration-induced white-finger (VWF) syndrome.

SUBJECTS AND METHODS

We studied 38 patients that were suffering from RP (primary RP, n=29; VWF, n=9) and 13 controls (six men and 45 women; mean age 49.1+/-11.6 years). Superficial finger skin blood flow was assessed with an infrared thermocamera before and after exposure to heat and cold. Fibrinogen, whole-blood viscosity and erythrocyte aggregation at different shear rates and plasma viscosity were measured.

MAIN RESULTS

In patients with RP finger temperatures after re-warming were lower than those in controls [right hand digit (DIG) I P<0.02; DIG II-V P<0.01; left hand DIG I P<0.01; DIG II-V p<0.02], male patients with primary RP had higher Fg-values (P<0.02) and a trend to higher plasma viscosity. Patients with VWF had a trend to lower plasma viscosity than controls. Whole-blood viscosity at each shear rate was highest in patients with VWF.

CONCLUSION

Provocation manoeuvres are essential in the diagnosis of RP. We speculate that the decreased plasma viscosity in VWF is a compensatory physiological mechanism, probably counteracting the chronic effects of vasospasm. The rise in whole-blood viscosity could be due to endothelial injury or to a reduction in the venous blood pH level. The abnormal cold reactivity of patients with RP may be partly related to rheological factors.

Pathogenesis of Raynaud's phenomenon

The pathogenesis of Raynaud's phenomenon is not fully understood. However, the last 20 yr have witnessed enormous increases in our understanding of different mechanisms which, singly or in combination, may contribute. A key point is that Raynaud's phenomenon can be either primary (idiopathic) or secondary to a number of underlying conditions, and that the pathogenesis and pathophysiology vary between these conditions. This review concentrates upon those subtypes of Raynaud's phenomenon of most interest to rheumatologists: systemic sclerosis-related Raynaud's phenomenon, primary Raynaud's phenomenon and Raynaud's phenomenon secondary to hand-arm vibration syndrome. In this review, I shall discuss the main mechanisms thought to be important in pathophysiology under the three broad headings of 'vascular', 'neural' and 'intravascular'. While these are false distinctions because all interrelate, they facilitate discussion of the key elements: the blood vessel wall (particularly the endothelium), the neural control of vascular tone, and the many circulating factors which can impair blood flow and/or cause endothelial injury. Vascular abnormalities include those of both structure and function. Neural abnormalities include deficiency of the vasodilator calcitonin gene-related peptide (released from sensory afferents), alpha(2)-adrenoreceptor activation (possibly with up-regulation of the normally 'silent' alpha(2C)-adrenoreceptor) and a central nervous system component. Intravascular abnormalities include platelet activation, impaired fibrinolysis, increased viscosity and probably oxidant stress. As our understanding of the pathophysiology of Raynaud's phenomenon increases, so do our possibilities for identifying effective treatments.

Nifedipine pretreatment reduces vibration-induced vascular damage

A rat-tail vibration model of hand-arm vibration was employed to test whether preemptive administration of nifedipine (5 mg/kg) to block vasoconstriction prevents vibration-induced arterial damage. The tails of vibrated and nifedipine-pretreated vibrated Sprague-Dawley rats were exposed continuously to 4 h of 60-HZ vibration at 49 m/s(2) rms. In nonvibrated anesthetized rats, the ventral tail arteries were bathed for 15 min in situ in 1 mM epinephrine or 1 mM norepinephrine to induce structural changes indicative of intense vasoconstriction. Arteries were processed for light and electron microscopy 45 min after treatment. Compared to sham control, 4-h vibration significantly (P < 0.01) reduced lumen size, generated endothelial disruption (7.0 +/- 2.6%), elevated nuclear factor of activated T cells c3 (NFATc3) expression in endothelial and smooth muscle cells, and increased smooth muscle cell vacuolization. The findings demonstrate that blockage of vibration-induced vasoconstriction with nifedipine prevents acute vascular damage. Smooth muscle and endothelial cells structurally altered by vasoconstriction are rendered susceptible to damage by vibration.

Laser Doppler anemometry distinguishes primary Raynaud phenomenon from VWF syndrome

OBJECTIVES

We evaluated two microcirculatory function-tests, the Laser Doppler (LD)-Anemometry and the Laser Doppler Imager (LDI)-Flowmetry in their value to further elucidate functional behavior of the "Vibration-induced white finger syndrome" (VWF) and to distinguish between Raynaud's phenomenon (RP) of idiopathic or vibration origin.

PARTICIPANTS AND METHODS

Ninety-four patients, suffering from RP were studied (78 patients with primary RP and 16 patients with VWF). Measurement of blood cell velocity (BCV) before and after provocation was obtained by nailfold capillary microscopy and an included Laser detector ("Anemometry"). Digital blood flux was recorded by LDI-Flowmetry during a standardized cooling and rewarming thermal challenge.

RESULTS

"Time to peak" of BCV, a measure of maximal reactive hyperemia was longer in VWF in comparison to primary RP (30.37 versus 19.29 sec P < 0.02), respectively.

CONCLUSION

Based on the fact, that prolongation of reactive hyperemia, an indicator of impaired endothelium-dependent vasodilation is also frequently found in peripheral arterial occlusive disease, it is hypothesized that VWF is not only a microcirculatory vasospastic disorder, but may also be related to atherosclerosis. Anemometry, in association with an appropriate provocation-test, could represent a useful non-invasive method for objectifying diagnosis of VWF in patients with RP.

Extracellular signal-regulated kinase activation and endothelin-1 production in human endothelial cells exposed to vibration

Hand-arm vibration syndrome is a vascular disease of occupational origin and a form of secondary Raynaud's phenomenon. Chronic exposure to hand-held vibrating tools may cause endothelial injury. This study investigates the biomechanical forces involved in the transduction of fluid vibration in the endothelium. Human endothelial cells were exposed to direct vibration and rapid low-volume fluid oscillation. Rapid low-volume fluid oscillation was used to simulate the effects of vibration by generating defined temporal gradients in fluid shear stress across an endothelial monolayer. Extracellular signal-regulated kinase (ERK1/2) phosphorylation and endothelin-1 (ET-1) release were monitored as specific biochemical markers for temporal gradients and endothelial response, respectively. Both vibrational methods were found to phosphorylate ERK1/2 in a similar pattern. At a fixed frequency of fluid oscillation where the duration of each pulse cycle remained constant, ERK1/2 phosphorylation increased with the increasing magnitude of the applied temporal gradient. However, when the frequency of flow oscillation was increased (thus decreasing the duration of each pulse cycle), ERK1/2 phosphorylation was attenuated across all temporal gradient flow profiles. Fluid oscillation significantly stimulated ET-1 release compared to steady flow, and endothelin-1 was also attenuated with the increase in oscillation frequency. Taken together, these results show that both the absolute magnitude of the temporal gradient and the frequency/duration of each pulse cycle play a role in the biomechanical transduction of fluid vibrational forces in endothelial cells. Furthermore, this study reports for the first time a link between the ERK1/2 signal transduction pathway and transmission of vibrational forces in the endothelium.

Hand function tests and questions on hand symptoms as related to the Stockholm workshop scales for diagnosis of hand-arm vibration syndrome

The severity of hand-arm vibration syndrome (HAVS) is usually graded according to the Stockholm workshop scales. Although the Stockholm workshop scales are regarded the gold standard for assessing the severity of HAVS, they are based primarily on subjective symptoms. The aim of the present study was to explore the agreement between Stockholm workshop scales and the outcome from ten well-defined clinical tests commonly used in hand rehabilitation for assessment of hand function. One hundred and eleven vibration-exposed workers participated in the study. Ten objective tests of hand function and four questions on subjective hand symptoms were included. The results indicated that, out of these tests, perception of vibration, perception of touch/pressure and dexterity showed a moderate agreement with Stockholm workshop scales. Among specific questions on hand symptoms, cold intolerance and pain showed a high agreement with Stockholm workshop scales. It is concluded that defined objective tests combined with directed questions on specific hand symptoms, together with the Stockholm workshop scales, may be helpful for diagnosing HAVS.

Vibration damage to the hand: clinical presentation, prognosis and length and severity of vibration required

Exposure to vibrating hand-held tools can cause a variety of vascular and neuromuscular symptoms collectively named Hand-Arm Vibration Syndrome (HAVS). The clinical presentation of this syndrome includes paraesthesiae or tingling in digits, pain or tenderness in the wrist and hand, digital blanching, cold intolerance, weakness of the finger flexors or intrinsic muscles and discolouration and trophic skin lesions of the fingers. HAVS can be reversible, at least in the earlier stages, but resolution of symptoms is unusual in more severe cases, and continued use of vibrating tools in such cases is unwise. The duration of exposure needed to produce HAVS cannot be readily defined. This is due not only to different individual susceptibilities to vibration, but also to the different physical characteristics of the vibration exposure. There is a cumulative effect of vibration on both the vascular and sensorineural components of HAVS and these components appear to occur and progress independently of each other.

Raynaud's phenomenon

Raynaud's phenomenon is characterised by episodic vasospasm of the fingers and toes typically precipitated by exposure to cold. Mild Raynaud's is common and is not usually a harbinger of clinically important disability; its onset, however, can be startling and uncomfortable for patients, and the well recognised association in some cases with systemic rheumatic conditions often precipitates aggressive assessments for underlying diseases. Advances in vascular physiology have shed light on the role of the endothelium as well as endothelium-independent mechanisms in the altered vasoregulation of Raynaud's. We review clinical aspects of the disorder and new insights with respect to pathophysiology, and we discuss potential new therapeutics based on the disease mechanism, such as prostacyclin analogues, serotonin antagonists, and calcitonin gene-related peptides.