Risk assessment for upper extremity work related muscoloskeletal disorders in different manufactures by applying six methods of ergonomic analysis

The risk assessment for Upper Extremities Work Related Muscle skeletal Disorders (UEWMSDs) remains a complex and open question. For professionals involved in this analysis of fundamental importance appears the use of technical/good practice norms or the guide lines produced by scientific society or association, such as for our country the guide lines published on this theme by the Italian Society of Occupational Medicine and Industrial Hygiene (SIMLII). The objective of this research was to verify and validate the multiple step method suggested by above mentioned guide lines and to compare results obtained by six analysis methods adopted (Washington State Standard, OCRA, HAL, RULA, OREGE and STRAIN INDEX (SI)).439 workstation in 17 manufactures employing 4166 workers for a total of 1396 analysis by different methods were considered, by adopting the following multiple step procedure: preliminary evaluation by Washington State method and OCRA checklist in all the working stations, RULA or HAL as first level evaluation, OREGE or SI as second level evaluation when complexity of work variables or contradictory results emerged. We have also collected data, provided by occupational physicians, about the pathologies of the upper limb. A representative sample of workers was also administered a INRS OREGE questionnaire that investigates the disorders of the upper limb, the subjective perception of risk, psychosocial factors and stress-related disturbs.The preliminary evaluation resulted negative (risk absent) in the 87\% of examined work stations and by using checklist OCRA optimal-acceptable condition was found in 57\% (the percentage reaches more than 90\% when classes of risk absent-very low-low risk classes of the method were considered all together), by HAL in 91\% of analysis, by RULA in 90\%, by OREGE in 58\%; by SI in 67\% of examined working position. Five methods have been contemporary used for 31 working position with the following results: 58\% at different degree of risk by OCRA, 13\% by HAL, 19\% by RULA; 13\% by OREGE; 10\% by SI. Among the main components of the bio mechanical risk the high frequency of working task resulted at first place for 4/5 methods and for checklist OCRA also the evaluation of recovery times. Consistent with the findings from risk assessment, the majority of reports of occupational diseases by occupational physician is localized at the wrist and workers assigned to tasks at risk not always have had occupational diseases. The role of main psychosocial factors was demonstrated in about the 15-20\% of working conditions and regarded in particular the working climate, the job maintenance perspective, the time pressure and errors possibility together with the difficulty of help by colleagues and managers and stress related disturbs.The preliminary evaluation by State of Washington method appears to be an adequate instrument for identify the working condition at risk. The results of this method appears well correlated with OCRA checklist and HAL. The risk conditions were always confirmed by higher complexity methods (RULA, OREGE, SI). All the adopted methods were in a good agreement in two extreme situations: high risk or absent risk. In the degree of accordance varied on the basis of their rationale and of the role of their different components. A necessary integration of biomechanical analysis appears the evaluation of working conditions and musculoskeletal and psychological disorders collected directly from the workers and the results of health surveillance programs. The recommendations of SIMLII about the critical use of biomechanical methods and about the possible use of more than one of them considering the working characteristics have been confirmed.