Median mononeuropathy among active workers: Are there differences between symptomatic and asymptomatic workers?

Abstract

The objective was to determine whether symptomatic workers with an abnormal sensory nerve conduction study consistent with carpal tunnel syndrome differed, in terms of electrophysiologic measures, psychosocial, demographic, anthropometric, or ergonomic variables, from workers with an asymptomatic median mononeuropathy. This was a cross‐sectional study of active workers at six different work sites. Cases were defined as workers with electrodiagnostic findings of a median mononeuropathy in either hand, based on a 0.5‐msec prolongation of the median sensory evoked peak latency compared to the ulnar latency. This group was stratified on the basis of symptoms of numbness, tingling, burning or pain in the hand. The two groups were compared in terms of demographic, anthropomorphic, psychosocial. electrophysiologic, and ergonomic risk factors. Active workers from six different sites were tested; five sites involved manufacturing workers, and one site represented clerical workers. One hundred eighty‐four active workers with a median mononeuropathy were documented on nerve conduction studies. These workers represented a subset of more than 700 workers screened at six different locations. The main outcome measure was the patient's report of symptoms of pain, numbness, tingling or burning in the hand or fingers that lasted more than 1 week or occurred three or more times at the initial screening. Workers with a median mononeuropathy who complained of hand symptoms were more likely to be female, to have jobs with higher hand repetition levels, to have higher ratings of job security, not to have a history of diabetes, to use more force in their job with more abnormal postures of their wrist and fingers, and to have a trend toward a more prolonged median sensory distal latency. Most logistic regression models explained less than 15% of the variance (pseudo R2). Women with jobs that have higher ergonomic risks and no history of diabetes were more likely to have reported symptoms associated with carpal tunnel syndrome compared to other workers with a documented median mononeuropathy. Psychosocial variables were not particularly discriminatory. None of the models allows enough precision to predict on an individual basis. Am. J. Ind. Med. 33:374–378, 1998. © 1998 Wiley‐Liss, Inc.

Role of physical load factors in carpal tunnel syndrome

“…In a cross-sectional study of 93 symptomatic and 91 asymptomatic active workers with median mononeuropathy (20.5 ms difference between the median and ulnar evoked peak sensory latency, 25% of the entire study population), Werner et a1 (71) found significant postural differences between the 2 groups in univariate analyses, including finger and wrist nonneutral postures. Other statistically significant differences between the 2 groups were gender, triceps skinfold thickness, history of diabetes, job insecurity, average hand force, and repetition level.…”

Common work-related musculoskeletal strains and injuries

“…1 Carpal tunnel syndrome (CTS) is one of the most common and disabling WMSDs, 6 affecting up to 25% of active workers. 3 The first published literature regarding diseases of workers was by Bernardino Ramazzini in 1700. His work is extensively cited in a recent article by Franco,7 who states that Ramazzini recognised that workers are susceptible to certain illnesses, and also noted that poor posture, repetitive movements and muscular loads contributed to certain disorders.…”

Síndrome do túnel do carpo: controvérsias a respeito de diagnóstico clínico e eletrofisiológico e a relação com o trabalho

“…Os estudos mais modernos sobre a prevalência de STC em trabalhadores foram realizados por pesquisadores da Ann Harbor University, Michigan, EUA 8,17,18 . Os três artigos referem-se a um grupo de cerca de 800 trabalhadores de atividades representativas da economia moderna frequentemente associadas com STC, como fabricação de móveis, contêineres, autopeças, velas de automóvel e processamento de dados.…”

“…Werner et al 17 não encontraram relação entre MM-0,5 (a "lesão") com atividade, mas relato de sintomas foi mais frequente em atividades de repetição alta e posturas forçadas do punho.…”

“…Os valores "anormais" em pessoas assintomáticas não são casos subclínicos de STC. Em um estudo de trabalhadores 17 , sintomas de STC desenvolveram-se em em 12% dos trabalhadores com condução sensitiva do mediano aumentada e em 10% dos trabalhadores com condução sensitiva normal, durante um seguimento de 10 a 24 meses. A concordância entre sintomas, exame físico e alterações eletrofisiológicas é baixa, tendo Homan et al 18 encontrado uma concordância de 5% entre os três parâmetros e Atroshi et al 9 encontraram 2,7%.…”