Can a battery of functional and sensory tests corrobrate the sensorineural complaints of subjects working with vibrating tools?

Objectives: The objective of the present paper is to study the relationship between the early sensorineural symptoms, classified according to the Stockholm scale, and the results of the main functional and sensory tests described in the literature, in subjects working with vibrating tools.
Methods: Three groups of male workers were selected from industry: one group (69 subjects) exposed to hand-arm vibration in several workplaces, one group (62) performing heavy and repetitive hand and arm work but without exposure to vibration, and one control group (46) performing light and non-repetitive tasks without vibration. All the workers were interviewed by questionnaire, about their personal characteristics, their health status, their actual and past working conditions and the episodes of tingling at the level of the fingers. From these reported symptoms, the sensorineural stage of the hand-arm vibration was determined using the Stockholm scale. Based on the review of the literature, we selected six functional and sensory tests: maximum voluntary grip force, maximum angles of the wrist, pressure perception threshold test, vibration perception threshold test, distal sensory latency and the Purdue Pegboard test. Each test was performed by the workers in the three groups.
Results: No main differences were observed between the personal characteristics of the three groups. According to the Stockholm scale, the sensorineural symptoms were mainly at stage SN1, with 9% at stage SN2 and none at stage SN3. These symptoms are associated with exposure to vibration, and had a prevalence of 40% in group 1, versus 20% in the two other groups. Furthermore, 25% of the workers exposed to vibration complained of symptoms at least once a week, compared with only 2% in the other groups. The multivariate logistic regression analysis showed an association between the existence of symptoms and a decrease in the maximum flexion angle of the wrist and an increase in the pressure perception threshold. This association, however, was too low to determine limit values with a sensitivity and specificity sufficiently high to make a reliable diagnosis.
Conclusions: The sensorineural symptoms at stage N1 on the Stockholm scale, experienced occasionally by some 40% of the users of vibrating tools, could not be corroborated by the functional and sensory tests.