Carpal tunnel syndrome (CTS) is a pattern of symptoms caused by damage, generally chronic, to the nervus medianus (median nerve), which is exposed to elevated pressure when it passes through the carpal tunnel. CTS constitutes the most common "bottleneck syndrome" of a peripheral nerve. It is caused by a range of factors, one of which is work-related manual stress. Since 2003, carpal tunnel syndrome has been listed by the European Commission in Annex I (506.45) of the European schedule of occupational diseases. With publication in May 2009 of the scientific reasoning for the recognition of CTS as an occupational disease, the medical advisory council for occupational diseases at the German Federal Ministry of Labour and Social Affairs (BMAS) followed by recommending that work-related CTS be included in the annex of the German Ordinance on occupational diseases. In the proposed legal definition, the scientific reasoning already states three risk factors: pressure damage to the nervus medianus in the carpal tunnel (carpal tunnel syndrome) caused by repetitive manual tasks involving bending and stretching of the wrists, exertion of elevated force by the hands, and hand-arm vibration. CTS may be caused by any one of these risk factors in isolation, or the risk of CTS may be exacerbated by combinations of two or all three factors. However, quantifiable parameters were not available for determining the level of exposure during investigations into and assessment of the work-related stresses.
The purpose of this project was to incorporate valid investigation and measurement data on CTS risk factors into a database in order to generate stress profiles from the data and ultimately to derive further recommendations for assessment of the work-related criteria for recognition of the occupational disease. The resulting findings were to be used for development of a CTS work history software application.
The Occupational Diseases committee of the directors' conference of the German Social Accident Insurance Institutions charged the Occupational Diseases Unit of the German Social Accident Insurance (DGUV) with forming an interdisciplinary and cross-institution CTS project group and a Working Techniques sub-group led by the IFA. The task of the group was firstly to produce, based upon the latest scientific findings, a guidance document and a template for comments for the purpose of exposure assessment, and secondly, to identify suitable measurement parameters for quantifying the stress factors. These measurement parameters were to be determined in accordance with a specific measurement report by means of an adapted CUELA system (CUELA: computer-aided measurement and long-term analysis of stress upon the musculoskeletal system) to which an EMG (eletromyography) module had been added. Muscle activity was to be recorded by means of the EMG for the purpose of estimating the gripping forces. Model measurements were to be conducted during the performance of vocational tasks which are stated in the scientific reasoning, or which would appear equivalent to them/relate to the reported cases of occupational diseases. Finally, the results were to be used to develop a software application for work histories in cases of occupational disease.
In line with its brief and with reference to the latest scientific findings, the group produced a guidance document and a template for comments by the prevention services regarding the work-related criteria for recognition of reported suspected cases of CTS. The group further prepared a publication containing recommendations for the handling of reported cases of occupational diseases with reference to the example of CTS; this publication was submitted in December 2013 to the journal Zentralblatt für Arbeitsmedizin, Arbeitsschutz und Ergonomie and approved for printing in January 2014.
Under the overall control of the IFA, the procedure described in the guidance document was implemented in a CTS work history software application. At the end of 2012, the software was made available to the German Social Accident Insurance Institutions for determining exposure in cases of CTS. Three central events were planned and held for application of the DGUV's CTS guidance document in general and of the CTS work history software for designated multipliers in particular.
Once suitable measurement parameters had been identified and the measurement report specified, 69 tasks exhibiting diverse stress profiles and in a range of sectors falling within the responsibility of eight accident insurance institutions were analysed between January 2011 and January 2014 in a total of 54 measurements. These studies enabled the analysis method to be improved further and adapted to the requirements. Four measurements were conducted in direct relation to reported suspected cases of occupational disease in which the measurement results provided an objective indication of the exposure. Based upon the results, the structure of a register of measured values was developed and the register populated with example data. A follow-up project is now to extend the register of measured values, integrate it into the CTS work history software application, and mutually adapt the two in further development.
-cross sectoral-Type of hazard:
musculoskeletal disorders (except cancer)Description, key words:
CTS (carpal tunnel syndrome), measurement of CTS risk factors, software application for occupational medical history, registry of measured values, database