External Orthopaedic Implants in the Magnetic Resonance Environment: Current Concepts and Controversies

MRI provides diagnostic three-dimensional imaging and remains extremely important in the diagnosis and management of spinal trauma as well as other acute traumatic injuries, including those of the extremities. The American Society for Testing and Materials has created standards against which all implantable medical devices are tested to ensure safety in an MR environment. Most implantable passive orthopaedic devices can undergo MRI without consequence to the patient. However, the American Society for Testing and Materials has recently updated its terminology resulting in confusion among providers and institutions. Primary safety concerns are radiofrequency-induced heating and magnetically induced torque or displacement. These safety concerns have emerged as a recent source of debate, particularly regarding the imaging of patients with external fixation and cervical immobilization devices in place. Surveys have shown a lack of consensus among radiologists regarding this issue. Having an institutional protocol in place for the imaging of these patients streamlines the diagnosis and early stabilization of certain polytraumatized patients. The purpose of this review is to summarize the pertinent literature as well as the current industry recommendations regarding the safety of commonly used external fixation, cervical immobilization, and traction devices in the MR environment.