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 o f sustaining impaired nerve conduction in the hands among vibration-ex posed persons as opposed to nonvibration-exposed referents. METHODS - In a cross-sectional study design platers and truck assembly workers w ere 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, respe ctively. 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 conduc tion velocity was slower in the right hand than in the left. An increa sed risk of prolonged latency time was found for the platers and assem blers when contrasted to the office workers. The relative risks (rate ratios) of impaired nerve conduction for the carpal tunnel segment var ied 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 hig her for the left-hand side than for the fight-hand side. The risks wer e not proportional to either the weighted or unweighted vibration expo sure. CONCLUSIONS - The contributions from vibration and ergonomic fac tors to impaired nerve conduction velocity were inseparable in this st udy. Ergonomic factors such as forceful gripping and extreme positions , apart from vibration exposure, may be strong determinants of impaire d nerve conduction in the carpal tunnel area.