Impaired nerve conduction in the carpal tunnel of platers and truck assemblers exposed to hand-arm vibration.

OBJECTIVES

The goal of this study was to assess the relative risks of sustaining impaired nerve conduction in the hands among vibration-exposed persons as opposed to nonvibration-exposed referents.

METHODS

In a cross-sectional study design platers and truck assembly workers were contrasted to office workers. The 4-h frequency-weighted vibration was 4.6 m.s-2 and 1.0 m.s-2 for the platers and assemblers, respectively. The ergonomic factors were measured as forced grip time. The conduction velocity, distal latency time, and amplitude of the median nerve were measured for both hands.

RESULTS

The sensory nerve conduction velocity was slower in the right hand than in the left. An increased risk of prolonged latency time was found for the platers and assemblers when contrasted to the office workers. The relative risks (rate ratios) of impaired nerve conduction for the carpal tunnel segment varied between 1.4 and 2.0 for the distal latency and between 0.9 and 1.7 for the nerve conduction velocity. The rate ratios were generally higher for the left-hand side than for the right-hand side. The risks were not proportional to either the weighted or unweighted vibration exposure.

CONCLUSIONS

The contributions from vibration and ergonomic factors to impaired nerve conduction velocity were inseparable in this study. Ergonomic factors such as forceful gripping and extreme positions, apart from vibration exposure, may be strong determinants of impaired nerve conduction in the carpal tunnel area.