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

Vibration transmitted to the hands of power drill operators: Effect of arm posture and type of drilled material

This study investigated the effect of the arm posture and the type of material on the vibration measured at the hands during drilling operation. An experiment was conducted using three different materials (concrete, steel, and wood) and two different arm postures characterized as 90° and 180° angle between the upper arm and forearm. Six male subjects stood on a force platform to measure and control the feed force during the drilling operation. The vibration was measured at the interface between the drill and both hands. The results showed that the effect of arm posture was dependent on the type of material being drilled. For example, drilling in concrete yielded higher frequency-weighted acceleration with the 90° arm posture than the 180° posture while drilling in wood showed an opposite trend. The results tend to suggest no correlation between the material hardness and the vibration at the hands. Higher vibration was also observed at the right hand than the left hand. It is recommended to not use the vibration emission data reported by manufacturers of power tools to evaluate incidences of hand-arm vibration syndrome (HAVS) but to rely on real measurements taken in the field under typical operating conditions.

Hand-arm vibration syndrome among harvesting farmers: A cross-sectional study from Pakistan

BACKGROUND

Constant use of hand-held vibratory tools may cause health issues, including hand dysfunction, among farmers. Thus, exposure to these vibratory instruments may cause hand-arm vibration syndrome (HAVS).

OBJECTIVE

The study aimed to measure the prevalence of HAVS and evaluate neurological and vascular symptoms among farmers.

METHODS

This cross-sectional study included 20 villages in Pakistan and used a three-part questionnaire to collect data from farmers exposed to vibration while farming. The study included demographics, the Health Surveillance Questionnaire, and the Stockholm Workshop Classification Scale. SPSS version 22 was used for the data entry and statistical analysis.

RESULTS

433 (43%) participants had musculoskeletal discomfort and 568 (57%) had hand vibration. Raynaud phenomenon was evident in 430 (43%) participants, whereas carpal tunnel syndrome was found in 218 (22%). Tingling was reported by 255 participants (26%), and numbness was reported by 543 (54%). According to the grading of neurological symptoms, 461 (46%) participants were exposed to vibration but did not experience any symptoms, placing them in stage 0. 185 (18.5%) participants with HAVS with infrequent episodes affecting just the tips of one or more fingers were categorized in stage 01 based on grading of vascular symptoms.

CONCLUSION

HAVS are common among harvesting farmers, with the most noticeable vibrations occurring in the shoulder region. Similarly, most farmers had no vascular symptoms, and most were exposed to vibration but had no neurological symptoms.

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

The effect of road-bike damping on neuromuscular short-term performance

The aim of this study was to understand if and how surface-induced vibrations and road bike damping affect short-term neuromuscular performance in cycling. Thirty cyclists (mass 75.9 ± 8.9 kg, height 1.82 ± 0.05 m, Vo2max 63.0 ± 6.8 ml/min/kg) performed steady-state and maximum effort tests with and without vibration exposure (front dropout: 44 Hz, 4.1 mm; rear dropout: 38 Hz, 3.5 mm) on a damped and a nondamped bike. Transmitted accelerations to the musculoskeletal system, activation of lower extremity muscles (gast. med., soleus, vast. med., rec. fem.) and upper body muscles (erec. spinae, deltoideus, tric. brachii), oxygen uptake, heart rate and crank power output were measured. The main findings indicate a transmission of vibration to the whole body, but since no major propulsive muscles increase their activation with vibration, the systemic energy demand increases only marginally with vibration. Damping reduces vibrations at the upper body, which indicates an increase in comfort, but has no effect on the vibration transfer to the lower extremities. Therefore, road bike damping does not affect neuromuscular response of the propulsive muscle groups and energy demand. Consequently, short-term power output does not increase with damping.

Hand-Arm Vibration Assessment and Changes in the Thermal Map of the Skin in Tennis Athletes during the Service

During recent years the number of tennis athletes has increased significantly. When playing tennis, the human body is exposed to many situations which can lead to human injuries, such as the so-called tennis elbow (lateral epicondylitis). In this work a biomechanical analysis of tennis athletes, particularly during the service, was performed, considering three different types of over-grip and the presence of one anti-vibrator device. One part of the study evaluates the exposure to hand-arm vibration of the athlete, based on the European Directive 2002/44/EC concerning the minimum health and safety requirements, regarding the exposure of workers to risks from physical agents. The second part of the study considers an infrared thermography analysis in order to identify signs of risk of injury, particularly tennis elbow, one of the most common injuries in this sport. The results show that the presence of the anti-vibrator influences the vibration values greatly in the case of athletes with more experience and also for athletes with less performance. The presence of the Cork and/or Tourna on the racket grip does not have any significant effect on the hand-arm vibration (HAV), similarly in the case of athletes with the best performance and athletes with less technique. The results indicated that the infrared thermography technique may be used to identify the risk of injuries in tennis players.

Experimental Modal Analysis of Hand–Arm Vibration in Golf: Influence of Grip Strength

Interest in the design of products that link performance and comfort is rapidly growing in the field of sport. To this end, the equipment industry is progressively shifting towards customization and it is focusing on man-machine interaction. The notion itself remains insufficiently studied by the scientific community. With regard to golf, several works conclude that vibrations that are perceived in the handle may be harmful and they have significant influence on comfort as well as performance. In that respect, the present paper investigates the effects of grip strength on three indicators of club dynamics: modal characteristics, overall vibratory levels, and vibration dose perceived by the club user, according to ISO 5349 standard. The study can be broken down into three steps. First, the experimental modal characteristics of a golf club are identified while using free-free, fixed-free, and grip-free (with three levels of grip strength) boundary conditions. Subsequently, a numerical model is developed and updated using experimental results. Finally, the root mean squared values and vibration dose transmitted to the hand-arm system after ball contact are extracted from the validated numerical model.

Can sensation of cold hands predict Raynaud's phenomenon or paraesthesia?

Background

Raynaud’s phenomenon and neurosensory symptoms are common after hand-arm vibration exposure. Knowledge of early signs of vibration injuries is needed.

Aims

To investigate the risk of developing Raynaud’s phenomenon and paraesthesia in relation to sensation of cold hands in a cohort of male employees at an engineering plant.

Methods

We followed a cohort of male manual and office workers at an engineering plant in Sweden for 21 years. At baseline (1987 and 1992) and each follow-up (1992, 1997, 2002, 2008), we assessed sensation of cold, Raynaud’s phenomenon and paraesthesia in the hands using questionnaires and measured vibration exposure. We calculated risk estimates with univariate and multiple logistic regression analyses and adjusted for vibration exposure and tobacco usage.

Results

There were 241 study participants. During the study period, 21 individuals developed Raynaud’s phenomenon and 43 developed paraesthesia. When adjusting the risk of developing Raynaud’s phenomenon for vibration exposure and tobacco use, the odds ratios were between 6.0 and 6.3 (95% CI 2.2–17.0). We observed no increased risk for paraesthesia in relation to a sensation of cold hands.

Conclusions

A sensation of cold hands was a risk factor for Raynaud’s phenomenon. At the individual level, reporting a sensation of cold hands did not appear to be useful information to predict future development of Raynaud’s phenomenon given a weak to moderate predictive value. For paraesthesia, the sensation of cold was not a risk factor and there was no predictive value at the individual level.

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.

Role of Kv4.3 in Vibration-Induced Muscle Pain in the Rat

We hypothesized that changes in the expression of voltage-gated potassium channel (Kv) 4.3 contribute to the mechanical hyperalgesia induced by vibration injury, in a rodent model for hand-arm vibration syndrome in humans. Here we show that the exposure of the gastrocnemius muscle to vibration injury induces muscle hyperalgesia that is accompanied by a significant downregulation of Kv4.3 in affected sensory nerve fibers in dorsal root ganglia. We additionally show that the intrathecal administration of antisense oligonucleotides for Kv4.3 messenger RNA itself induces muscle hyperalgesia in the rat. Our results suggest that attenuation in the expression of Kv4.3 may contribute to neuropathic pain in people affected by hand-arm vibration syndrome.

PERSPECTIVE

Our findings establish Kv4.3 as a potential molecular target for the treatment of hand-arm vibration syndrome.

Work ability in vibration-exposed workers

Background

Hand–arm vibration exposure may cause hand–arm vibration syndrome (HAVS) including sensorineural disturbances.

Aims

To investigate which factors had the strongest impact on work ability in vibration-exposed workers.

Methods

A cross-sectional study in which vibration-exposed workers referred to a department of occupational and environmental medicine were compared with a randomized sample of unexposed subjects from the general population of the city of Gothenburg. All participants underwent a structured interview, answered several questionnaires and had a physical examination including measurements of hand and finger muscle strength and vibrotactile and thermal perception thresholds.

Results

The vibration-exposed group (47 subjects) showed significantly reduced sensitivity to cold and warmth in digit 2 bilaterally (P < 0.01) and in digit 5 in the left hand (P < 0.05) and to warmth in digit 5 in the right hand (P < 0.01), compared with the 18 referents. Similarly, tactilometry showed significantly raised vibration perception thresholds among the workers (P < 0.05). A strong relationship was found for the following multiple regression model: estimated work ability = 11.4 − 0.1 × age − 2.3 × current stress level − 2.5 × current pain in hands/arms (multiple r = 0.68; P < 0.001).

Conclusions

Vibration-exposed workers showed raised vibrotactile and thermal perception thresholds, compared with unexposed referents. Multiple regression analysis indicated that stress disorders and muscle pain in hands/arms must also be considered when evaluating work ability among subjects with HAVS.

The association between vibration and vascular injury in rheumatic diseases: a review of the literature

Vascular manifestations can be seen early in the pathogenesis of inflammatory rheumatic diseases. Animal experiments, laboratory and clinical findings indicated that acute or long-term vibration exposure can induce vascular abnormalities. Recent years, in addition to Raynaud's phenomenon (RP), vibration as a risk factor for other rheumatic diseases has also received corresponding considered. This review is concentrated upon the role of vibration in the disease of systemic sclerosis (SSc). In this review, we are going to discuss the main mechanisms which are thought to be important in pathophysiology of vascular injury under the three broad headings of "vascular", "neural" and "intravascular". Aspects on the vibration and vascular inflammation are briefly discussed. And the epidemiological studies related to vibration studies in SSc and other rheumatic diseases are taken into account.

Physical capacity and psychological mood in association with self-reported work ability in vibration-exposed patients with hand symptoms

BACKGROUND

The aim of this study was to investigate whether self-reports of work ability correlated to the results of quantitative tests measuring physical capacity and a questionnaire assessing psychological mood in vibration-exposed patients with hand symptoms.

METHODS

The participants comprised 47 patients (36 men and eleven women) with exposure to hand vibration and vascular and/or neurological symptoms in the hands. They performed several quantitative tests (manual dexterity, hand grip strength, finger strength) and completed the Work Ability Index (WAI) and Hospital Anxiety and Depression Scale (HADS) questionnaires.

RESULTS

Correlation analysis revealed statistically significant associations between the WAI results, the HADS indices, hand grip and finger strength, and manual dexterity measured using the Purdue Pegboard®. Multiple regression analysis revealed age and HADS indices as the strongest predictors of work ability.

CONCLUSIONS

The patient's age and psychological mood may be stronger predictors of work ability compared with results from tests measuring physical capacity of the hands in vibration-exposed patients with hand symptoms. When using the WAI as an instrument for assessing work ability in these patients, health care providers need to be more aware of the impact of the psychological mood.

Vibration from a riveting hammer causes severe nerve damage in the rat tail model

INTRODUCTION

Hand-arm vibration syndrome (HAVS) is an occupational neurodegenerative and vasospastic disorder in workers who use powered hand tools. Frequency weighting (ISO 5349) predicts little risk of injury for frequencies >500 HZ. Potentially damaging high frequencies abound in impact tool-generated shock waves.

METHODS

A rat tail impact vibration model was developed to deliver shock-wave vibration from a riveting hammer to simulate bucking bar exposure. Rat tails were vibrated continuously for 12 min. Tail flick withdrawal times were determined for noxious heat. Nerve trunks and skin were processed for light and electron microscopy.

RESULTS

Immediately after vibration, the tails were hyperalgesic and had disrupted myelinated axons, fragmented nerve endings, and mast-cell degranulation. By 4 days, the tails were hypoalgesic; nerve endings were lost in the skin.

CONCLUSIONS

Shock-wave vibration causes severe nerve damage. Frequency weighting seriously underestimates the risk of nerve injury with impact tools.

Neuropathic pain-like alterations in muscle nociceptor function associated with vibration-induced muscle pain

We recently developed a rodent model of the painful muscle disorders induced by occupational exposure to vibration. In the present study we used this model to evaluate the function of sensory neurons innervating the vibration-exposed gastrocnemius muscle. Activity of 74 vibration-exposed and 40 control nociceptors, with mechanical receptive fields in the gastrocnemius muscle, were recorded. In vibration-exposed rats ∼15% of nociceptors demonstrated an intense and long-lasting barrage of action potentials in response to sustained suprathreshold mechanical stimulation (average of 2635 action potentials with frequency of ∼44Hz during a 1min suprathreshold stimulus) much greater than that has been reported to be produced even by potent inflammatory mediators. While these high-firing nociceptors had lower mechanical thresholds than the remaining nociceptors, exposure to vibration had no effect on conduction velocity and did not induce spontaneous activity. Hyperactivity was not observed in any of 19 neurons from vibration-exposed rats pretreated with intrathecal antisense for the IL-6 receptor subunit gp130. Since vibration can injure peripheral nerves and IL-6 has been implicated in painful peripheral neuropathies, we suggest that the dramatic change in sensory neuron function and development of muscles pain, induced by exposure to vibration, reflects a neuropathic muscle pain syndrome.

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.

Behavioural treatment of post‐traumatic and vibration‐induced digital cold sensitivity

Cold sensitivity is a common problem after all types of hand injuries. The aim of the present study was to assess possible effects of treatment by Pavlovian conditioning, a behavioural treatment method for digital cold sensitivity where whole body cold exposure becomes associated with warm hands. Eighteen hand-injured patients and nine patients with vibration-induced problems in their hands completed the treatment. Questionnaires and questions, assessment of perception of touch/pressure and skin temperatures after cold provocation, was made before and after the completed period of treatment and after 6 and 12 months. The results indicated subjective improvement in the hand-injured group in contrast to a lack of response in the vibration group. An increased digital skin temperature after treatment was noted for the vibration-exposed group only, which however did not persist at 6 and 12 months' follow-up.

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.

Increased oxidant activity mediates vascular dysfunction in vibration injury

Occupational exposure to hand-operated vibrating tools causes a spectrum of pathological changes in the vascular, neurological, and musculoskeletal systems described as the hand-arm vibration syndrome (HAVS). Experiments were performed to determine the effects of acute vibration on the function of digital arteries. Rats paws were exposed to a vibrating platform (4 h, 125 Hz, constant acceleration of 49 m/s(2) root mean squared), and digital artery function was assessed subsequently in vitro using a pressure myograph system. Constriction to phenylephrine or 5-hydroxytryptamine was reduced in digital arteries from vibrated paws. However, after endothelium denudation, constriction to the agonists was no longer impaired in vibrated arteries. Inhibition of nitric-oxide synthase (NOS) with N(omega)-nitro-l-arginine methyl ester (l-NAME) increased constriction to phenylephrine or 5-hydroxytryptamine in vibrated but not control arteries and abolished the vibration-induced depression in constrictor responses. However, nitric oxide (NO) activity, determined using the NO-sensitive probe 4-amino-5-methylamino-2', 7'-difluorofluorescein, was reduced in vibrated compared with control arteries. Endogenous levels of reactive oxygen species (ROS), determined using the ROS-sensitive probe 5-(and 6)-chloromethyl-2',7'-dichlorodihydro-fluorescein, were increased in vibrated compared with control arteries. The increased ROS levels were abolished by L-NAME or by catalase, which degrades extracellular hydrogen peroxide. Catalase also increased constriction to phenylephrine or 5-hydroxytryptamine in vibrated but not control arteries and abolished the vibration-induced depression in constrictor responses. The results suggest that acute vibration causes vascular dysfunction in digital arteries by increasing ROS levels, which is probably mediated by uncoupling of endothelial NOS. Therefore, therapeutic strategies to inhibit ROS or augment NO activity may be beneficial in HAVS.

An investigation on the biodynamic foundation of a rat tail vibration model

The objectives of this study are to examine the fundamental characteristics of the biodynamic responses of a rat tail to vibration and to compare them with those of human fingers. Vibration transmission through tails exposed to three vibration magnitudes (1 g, 5 g, and 10 g r.m.s.) at six frequencies (32 Hz, 63 Hz, 125 Hz, 160 Hz, 250 Hz, and 500 Hz) was measured using a laser vibrometer. A mechanical-equivalent model of the tail was established on the basis of the transmissibility data, which was used to estimate the biodynamic deformation and vibration power absorption at several representative locations on the tail. They were compared with those derived from a mechanical-equivalent model of human fingers reported in the literature. This study found that, similar to human fingers, the biodynamic responses of the rat tail depends on the vibration magnitude, frequency, and measurement location. With the restraint method used in this study, the natural frequency of the rat tail is in the range 161-368 Hz, which is mostly within the general range of human finger resonant frequencies (100-350 Hz). However, the damping ratios of the rat tail at the unconstrained locations are from 0.094 to 0.394, which are lower than those of human fingers (0.708-0.725). Whereas the biodynamic responses of human fingers at frequencies lower than 100 Hz could be significantly influenced by the biodynamics of the entire hand-arm system, the rat tail biodynamic responses can be considered independent of the rat body in the frequency range used in this study. Based on these findings it is concluded that, although there are some differences between the frequency dependences of the biodynamic responses of the rat tail and human fingers, the rat tail model can provide a practical and reasonable approach to examine the relationships between the biodynamic and biological responses at midrange to high frequencies, and to understand the mechanisms underlying vibration-induced finger disorders.

Treatment of chronic digital ischemia with direct microsurgical revascularization

The authors present their technique for treating digital ischemia using a radial-to-digital artery bypass graft performed in a bloodless field under tourniquet with the use of a microscope. The outcomes in 6 patients were resolution of fingertip ulcers, avoidance of more proximal amputations, and elimination of ischemic pain.

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.

Pathologic Conditions of the Hypothenar Eminence: Evaluation with Multidetector CT and MR Imaging

Pain, weakness, and sensory loss occur frequently in the hypothenar eminence. However, clinical examination is difficult and nonspecific, and the prescribed imaging technique may be inadequate, or images may be misinterpreted. Different imaging modalities have various degrees of usefulness for the diagnosis of painful pathologic conditions of the hypothenar eminence. Radiography, multidetector computed tomography (CT), multidetector CT arthrography, and magnetic resonance (MR) imaging of the wrist are useful for surveying the anatomy of the hypothenar eminence, the Guyon canal, and the ulnar nerve and artery and for determining the cause of pain or other symptoms. A fracture of the pisiform bone or the hook of the hamate bone, osteoarthritis or osteochondromatosis of the pisotriquetral joint, Guyon canal syndrome, hypothenar hammer syndrome, tendinopathy of the flexor carpi ulnaris, an anomalous muscle, a ganglion cyst, or a tumor may be responsible for ulnar neuropathy. Specific radiographic views, such as the semisupinated oblique view and the lateral view with the hand radially deviated and the thumb abducted, often provide a sufficient basis for the diagnosis of acute fracture of the hook of the hamate or the pisiform bone. Multidetector CT angiography is an efficient method for diagnosing hypothenar hammer syndrome, and multidetector CT arthrography is well suited for evaluation of the pisotriquetral joint. MR imaging is the modality of choice for depiction of the ulnar nerve.

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.

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.

Hand muscle weakness in long-term vibration exposure

Hand muscle strength was compared between workers regularly exposed to hand-held vibrating tools (n=81) and a non-exposed control group (n=45). Maximal voluntary strengths of hand grip, thumb pinch, thumb palmar abduction and index and little finger abduction were measured. The exposed workers had significantly weaker extrinsic (7%, P<0.01) and intrinsic (19%, P<0.0001) muscles than the controls. Reduced vibration perception was noted in nine vibration-exposed workers who presented with symptoms of hand muscle weakness (P<0.01). Cold intolerance following vibration exposure was found to precede sensorineural and vasospastic symptoms. We therefore postulate that cold intolerance may be a valuable marker for early detection of the adverse effects of vibration. This study emphasizes the need for tests of intrinsic muscle strength in order to evaluate the impairment of hand function observed in vibration-exposed workers.

Hand-arm-vibration syndrome (HAVS): is there a central nervous component? An fMRI study

Hand-held vibrating tools may result in neuromuscular dysfunction and vasospastic problems of the hand. Sensory and motor dysfunction can be explained by injury to peripheral structures, but could also be due to changes in cortical somatotopic mapping of the hand in the brain. The purpose of the present study was to use functional magnetic resonance imaging (fMRI) to assess the somatotopic cortical representation of the hands of workers subjected to occupational vibration. The study included six men with severe vibration exposures who were suffering from hand-arm-vibration syndrome (HAVS) and six controls. The analysis focused on the pattern and degree of activation of contra- and ipsilateral hemispheres of the brain with tactile stimulation and motor activation of the hand. These stimulations resulted in well-defined activation of the contralateral, and to a lesser extent the ipsilateral hemisphere. Statistical analysis of this limited patient material did not indicate any significant somatotopic cortical changes following long-term exposure to vibrating hand-held tools, although there was a tendency to a shift of activation towards the more cranial parts of the cortex in the patient group.