Numerical assessment of induced electric fields in a worker’s hand with commonly used metallic implants under exposure to low frequency magnetic fields

Abstract

The European Union’s Workers' Directive 2013/35/EU on the minimum health and safety requirements regarding the exposure of workers to electromagnetic fields specifies action levels (AL) for external electric and magnetic fields, which should protect against induced tissue-internal electric field strength Ei above the exposure limit values (ELV), the latter being defined in order to prevent tissue stimulation at low frequencies. However, although 2013/35/EU explicitly calls for the protection of “workers at particular risk” (including workers with metallic implants), the AL specified in the Directive have been derived under the assumption that there are no metallic parts present inside the body.
Therefore, in the present work, we analyzed the situation of a worker’s hand and forearm bearing metallic implants (Herbert screw and volar radius plate) used for osteosynthesis after the most common bone fractures of the hand/forearm, exposed to low frequency magnetic fields. The uniform exposure of the whole hand and forearm as well as the exposure to a specific and widely used device, a deactivator for single-use labels of acousto-magnetic electronic article surveillance (AM-EAS) systems, were considered based on numerical computations using a high-resolution anatomical hand/forearm model.
The results obtained indicated that the maximum induced electric field strength averaged in a volume of 2 mm × 2 mm × 2 mm cube was higher in the presence of the metallic implants by a factor of up to 4.2 for bone tissue and 2.3 for soft tissue compared with the case without an implant. Hence, it is obvious that the local induced electric field strengths may be substantially increased by the implants. The extent of this increase, however, is highly dependent on the implant’s position inside the body, the implant’s geometry, and the field distribution and orientation with respect to the anatomical structure and the implant.