The correlation between symptoms and ­electromyography findings in workers exposed to vibration and overloading of upper limbs

Summary

Peripheral nerves diseases of upper limbs as result of exposure to vibrations and local muscular load are long-term the most common occupational disease in the Czech Republic. In spite of that the electromyography (EMG) examination in workers exposed to vibration and local muscular load was included in the fundamental content of entry and exit medical examinations in Annex 2 of Decree No. 79/2013 Coll., about occupational health services. During periodic examinations is usually recommended, as yet, to indicate EMG examination only on the basis of typical subjectively reported problems. The aim of the study was to find out the extent of subjective symptoms related to peripheral nerve disorders of the hands that can be relied on when electromyography examination in occupational health examinations is indicated.

The epidemiological study followed up 2 samples. The first one included 215 men who work in the third risk category of above the threshold vibration transmitted to the upper limbs from the large ironwork and steel company. The other sample consisted of 236 women working in the third risk category of above the threshold local muscular load of hands from the large assembly company. The data on health status, occupational exposure, specific subjective symptoms related to peripheral nerve disorders of upper limbs, and the results of the objective EMG examination was obtain from medical records of occupational health examinations. All analyses were performed in STATA version 10.

The results of subjective symptoms validity evaluation referring to peripheral nerve disorders of hands according the results of objective EMG examinations showed a very low sensitivity in both samples – 39% of men in the risk of vibration and 31% of women in risk of overloading of hands. The lowest sensitivity values at all were indicated in entry examinations – i.e. in 23% of men and 16 % of women, the highest values in exit examinations – in 50% of men and 66% of women. Although the sensitivity of reported symptoms increased with the severity of EMG findings in the most serious of motor disorders reached only 58% in men and 55% in women. Other results of the epidemiological study confirmed the statistically significant correlation between the worsening EMG finding and increasing age (p < 0.001), exposure duration (p <0.001) and increasing BMI (p < 0.001), and that in the both of investigated groups of men and women.

It can be concluded that in practice can not be relied on the workers with peripheral nerve harm of the upper limbs would admit their disorders within occupational health examinations. The outputs of this study supported the correctness of the EMG examination inclusion in basic contents of entry and exit medical examinations in workers exposed to vibration and strain of the upper limbs, as shown in the annex of the Decree on occupational health services. This indication is limited only to forensic reasons. Regarding the occupational health protection, a preventive point of view is fulfilled by indication of the EMG test in periodic medical examinations, however this issue remains open.

Keywords:
occupational peripheral nerve disorders – vibration – overloading of hands – symptoms sensitivity – electromyography – occupational medical examinations