Cumulative trauma disorders.
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A method of describing the musculoskeletal loads in the hand and wrist during manual tasks is presented. A profile of twelve factors is used to quantify the exposure of applicable soft tissues to modes of loading suggested as being related to a number of chronic, work-related musculoskeletal disorders such as chronic muscle strain, tenosynovitis, and carpal tunnel syndrome. These factors include estimates of tendon loads and movement, frictional work done on the tendon sheaths, and muscle activation determined using electromyography. The response of these measures to changes of force, repetition, and posture was studied using eight conditions of a simulated task utilizing a pistol grip tool. Measures of tendon frictional work and dynamic electromyographic activity best paralleled the injury outcomes of an epidemiological study using similar task definitions (Silverstein et al. 1986). This field-usable system is being used currently to investigate the relationship between occupational exposure and musculoskeletal disorders.
PURPOSE/METHOD: Early diagnosis of Carpal Tunnel Syndrome (CTS) is essential for its effective treatment and subsequent reduction or prevention of the personal and economic losses associated with it. This paper describes a comparison of vibration threshold testing (VTT) and nerve conduction testing (NCT) within the same subjects. RESULTS: Across age and diagnostic category there was little difference between VTT results and the NCT velocity measure in their ability to identify individuals with CTS. CONCLUSION: This is important because VTT is more easily administered and tolerated than NCT and can be used in general screening studies to identify potential CTS cases.
Surveillance for musculoskeletal disorders of the upper extremity in industry is in its infancy. Research efforts to elucidate the causal factors of these disorders often rely on either the analysis of existing medical records, worker compensation records (passive surveillance), or the surveying of workers with questionnaire and physical examination (active surveillance). The use of either type of data for routine surveillance presents several difficulties illustrated with the results presented in this paper. The analysis of existing records is generally less costly but the reliability of the data is difficult to assess. Standardized questionnaire and physical examinations can be as sensitive as the use of unusually thorough existing occupational medical records; however, it is unclear whether the additional cost of an active surveillance system will deter the routine use of such systems.
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Chronic tendon and nerve disorders of the upper extremity, such as tendinitis and carpal tunnel syndrome, are a common problem among persons who routinely perform hand-intensive work. This article summarizes the most commonly reported occupational risk factors: repetitiveness, forcefulness, certain postures, mechanical stresses, exposure to vibration, and exposure to low temperatures. It describes how to look for these factors and how to control them through the design of work equipment and procedures.
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1. Ergonomic hazards impact employers and workers and their families. Poor workplace design, awkward body mechanics or postures, repetitive movements, and other ergonomic hazards induce or contribute to a staggering number of cumulative trauma disorders. 2. Cumulative trauma disorders (CTD) affect hands, wrists, elbows, arms, shoulders, the lower back, and the cervical spine area. Structures involved include tendons, muscles, bones, nerves, and blood vessels. One can plan strategies for abatement by learning to recognize the hazards that contribute to CTD. 3. OSHA has published the Ergonomic Program Management Guidelines. OSHA has also given Advance Notice of Proposed Rulemaking for an Ergonomic Standard that will affect all industries. 4. A company wide ergonomic assessment should be developed, followed by a well written ergonomic plan. Ergonomic abatement will decrease the costs associated with CTD and ultimately impact the corporate "bottom line."
The occupational use of video display terminals (VDTs) has been associated with the increasing incidence of upper extremity musculoskeletal disorders, often called cumulative trauma disorders. To guide clinical and policy decisions about the prevention and treatment of these VDT related disorders, valid and economic measures of total daily VDT use and VDT related job tasks such as data entry or editing will be important. In this study of newspaper reporters and copy editors (n = 83), VDT use was measured with employee self reports and by sampling the work behaviors of a subsample of employees. Behavioral sampling estimated VDT use as a characteristic of the job as opposed to a characteristic of individual employee performance. Overall, the two techniques of measuring occupational VDT use compared favorably, with the exception that self reported hours of VDT use tended to exceed the hours of use estimated by behavioral observation for employees who were younger and those who reported greater job demands. The findings suggest that behavioral sampling is a valid technique for estimating VDT use as a job characteristic.
In the mid-1980s, use-related arm pain was recognized as a major issue for worker health and workplace safety. National policy targeted these "cumulative trauma disorders," "overuse syndromes," and "motion illnesses" for a "special emphasis program" by the Occupational Safety and Health Administration, a federal regulatory agency. The program begins with case recognition to identify the responsible ergonomic hazards with the goal of mandating ergonomic remedies. This report is a small area analysis of the impact of this process on the US West Communications, Inc work force. US West employs some 55,000 workers in 14 states. Commencing in the mid-1980s, workers in four of these states complained of upper extremity pain and were diagnosed as suffering from conditions encompassed by the "cumulative trauma disorders" rubric. The incidence was tenfold higher in one task category, directory assistance operators. No ergonomic descriptor can account for the four endemics of arm pain in directory assistance operators. The response of the medical communities to the plight of these injured claimants varied considerably from community to community. Denver represents one extreme where the clinical judgments led to multiple surgical interventions, generated a total direct cost of some $1.5 million, and left many permanently disabled workers in their wake. This analysis raises many reservations about the validity of the "cumulative trauma disorder" hypothesis and provides an object lesson in the potential for untoward outcomes from the premature introduction of clinical hypotheses into the arena of health policy.
The clinical management of cumulative trauma disorder is based upon the identification and treatment of individual component pathologies and, frequently, referral to a knowledgeable occupational therapist with an understanding of ergonomic behavioral, postural, and workspace modification. Most commonly these individual pathologic entities are carpal tunnel syndrome, cubital tunnel syndrome, trigger finger, and De Quervain's tenosynovitis. In this article, the anatomy, diagnosis, and treatment of each of these disorders will be considered separately. In addition, since these clinical entities are often use-related, special attention should be directed toward biomechanical and ergonomic considerations.
The purpose of this study was to establish a simple observation to help in distinguishing patients who are giving their maximal effort during computer-assisted grip strength measurements from those who are not. Preliminary observations had suggested that maximal effort with this grip-strength device was characterized by greater force in the radial digits than the ulnar digits and a small variability in force between individual grasps. These observations were then prospectively analyzed in the following groups: (a) 178 assembly workers tested during a routine screening at a computer manufacturing company and during pre-placement physicals; (b) 196 workers with a hand injury or cumulative trauma disorder who were seeking consultation for medical treatment; (c) 55 workers with a hand injury or cumulative trauma disorder being measured to determine their return to work status or impairment rating; and (d) 58 asymptomatic volunteers. The volunteers were instructed to perform the maximal grip in the same fashion as the other groups and then to repeat the test exerting a submaximal effort they estimated to be 50% of their own maximal effort. The results of this study demonstrated that there is a highly significant association, P < 0.001, between the presence of a "total pattern" (radial over ulnar force being less than 1.0, unilateral grip variation greater than 15%, and difference between the left and right grip variation greater than 5%) and the presence of submaximal effort during grip-strength measurements.
Little is known about the mechanisms that underlie the pathophysiology involved in the development of cumulative trauma disorders. Musicians, specifically string players, may be a useful model to examine the cumulative effects of repetitive motion given the highly attended movements of their left hands and the stereotypical grasp of their right hands. Musculoskeletal disorders related to playing are experienced by 39% to 87% of musicians, making musicians a potentially good model for the study of factors involved in development of cumulative trauma disorders. Sensory thresholds for two-point discrimination and light touch were measured in all phalanges of each digit, of each hand. Comparisons were made within and between a control group of 10 nonmusicians who did not engage in repetitive motion and 10 healthy musicians who did. There were 5 violinists, 2 violists, and 3 cellists. The Non-musician group perceived two-points and light touch at significantly lower thresholds in the proximal phalanges of the left hand than the right hand. Significant differences were not present between right and left hands for the means of distal, middle, and proximal phalanges of the Musician group. This lack of significant difference may be due to higher sensory thresholds associated with repetitive use of the left hand of the musicians.
BACKGROUND: Upper extremity cumulative trauma disorders (CTDs) are among the most prevalent and costly occupational injuries. These disorders include nerve compression syndromes, tenosynovitis, epicondylitis, tendinitis, and arthritis. These have been related in the past to repetitive use of the upper extremity. The expected increase in the age of the American work force and the assumption that older workers are more susceptible to the disorders prompted this investigation of the relationship of age to signs and symptoms of upper extremity impairment. METHODS: A battery measuring seven objective signs and four reported symptoms of upper extremity cumulative trauma disorders was administered to two stratified random samples of workers. One group (n = 157) processed cooked poultry and the second group (n = 118) performed data entry at VDT terminals. Workers were separated into three age groups (younger: 20-35 years, middle-aged: 36-50 years, and older: 51-71 years). RESULTS: A series of analyses of variance were computed to determine whether the older workers were more impaired. No significant age differences were found for sign, symptom, or total scores in either sample, and no significant Age x Gender interaction was present. Older workers were more impaired for vibratory sensation, cutaneous pressure, and motor latency. CONCLUSIONS: The results support the hiring of older workers for general tasks in the workplace without significant worry of increased susceptibility to CTDs.
OBJECTIVE: To assess the biomechanical impact of commercially available alternate keyboard designs.DESIGN. A repeated measures study was conducted in a laboratory setting, with planned comparisons of Pitch, Roll and Yaw angles of the keyboards. Ten keyboard conditions were tested. Dependent measures included tendon travel, wrist deviations, and wrist and finger kinematics.BACKGROUND. Various alternate keyboard designs have recently been introduced, which vary Pitch, Roll and Yaw angles, separation distance between keyboard halves, and include other novel features such as cup-shaped depressions for the keys. Yet little objective research has been conducted regarding the biomechanical implications of these various design features. This study attempts to quantify the keyboard designs in terms of several recognized risk factors associated with cumulative trauma disorders that arise with repetitive typing. METHODS: Wrist and finger goniometers were used to measure joint motions during a standardized typing task. 15 experienced typists (8 women, 7 men) served as subjects. Regression equations were used to generate estimates of tendon travel.RESULTS. Tendon travel was affected primarily by Pitch but not Roll or Yaw angles while wrist deviations responded to changes in all three angles. Males had significantly greater amount of tendon travel than female subjects; this difference was only partially accounted for by anthropometry. Differences in joint motion may have a greater impact on the amount of tendon travel.CONCLUSIONS. Alternate keyboard designs can affect tendon travel by as much as 11%. RelevanceAs various alternate keyboard designs are marketed, quantifiable biomechanical data such as that provided by this study, will help to assess their impact on the risk factors for cumulative trauma disorders.
Electromyography (EMG) has been proposed as a method for determining muscle effort in repetitive upper limb tasks, which are often related to cumulative trauma disorders. EMG activity of the finger flexor musculature was investigated during a repetitive hand gripping task having 5 different cycle durations (2 to 6 s), various percentage of work time (and rest) within the work cycle (20% to 80%), and 3 different grip force levels. Thirty healthy adult participants each performed 27 randomly ordered 30-s repetitive hand gripping trials as well as 3 isometric contractions, which were used to normalize data from the hand gripping trials. There was a significant decrease in mean EMG as the duration of the work-rest cycle time increased. At each force level, EMG increased as the percentage of work time within the work-rest cycle increased, but to a greater extent at the highest force level. The results of this study suggest that overall muscle effort, and perhaps muscle fatigue, can be reduced most effectively by modifying the force requirements of the repetitive task. Other variables, such as the percentage of work time within a cycle and overall work cycle time have less effect on the EMG activity level. The results of this study have implications for developing strategies to reduce muscle fatigue during repetitive hand gripping tasks in an effort to reduce the effects of cumulative trauma disorders.
Disability from work-related arm pain has become prevalent in several countries in recent years. Many of these individuals present with chronic musculoskeletal symptoms that, for lack of a more specific diagnosis, are often labeled as a repetitive strain injury or cumulative trauma disorder. Indemnity for such conditions can be contentious; many of these sufferers are involved in litigation in their quest for financial compensation for temporary or permanent disability. This article describes our experience with 103 patients referred to a Health Reference Center for Workers for the management of repetitive strain injury. Their illness is far more global than the work-related arm pain that such labeling implies. From the total group, 73 fulfilled the American College of Rheumatology Criteria for the Classification of Fibromyalgia Syndrome. This means that they were suffering pain above and below the diaphragm, far from the arm pain for which they were referred. These 73 patients were clinically and psychologically indistinguishable from 165 patients followed in our clinic at the Federal University of São Paulo, Rheumatology Division, who also fulfilled these criteria but did not consider their illness work-related. This observation calls for longitudinal investigations that might offer insights as to whether the more global aspects of the illness are antecedent, coincident, or confounding aspects of the illness experience labeled repetitive strain injury or cumulative trauma disorder.