Fixed, Internal, Passive, Orthopaedic Implants

Information for patients

If you are a patient reading this and have a concern about an MRI scan you are scheduled to attend, we strongly recommend you contact the site where your scan is due to take place, you may also wish to refer to our ‘Information for Patients’ section. Please note local variations to the policies detailed on this website may apply, therefore please contact the hospital where your appointment is scheduled for clarification.

Disclaimer (MUST READ)

The MRI safety information contained within this webpage is intended for use by staff from NHS Greater Glasgow and Clyde (GGC) and associated health boards, namely: NHS Ayrshire and Arran, NHS Borders, NHS Dumfries & Galloway, NHS Forth Valley, NHS Golden Jubilee, and NHS Lanarkshire. Only staff from these health boards are approved to use this information and local variations to the policies detailed may apply.  Non-approved users i.e. patients and staff from health boards other than those listed above, or staff from private medical organisations use this information at their own risk. We, NHS GGC, accept no responsibility for patient injury or adverse outcomes that may occur as a consequence of the information contained herein. If you have any questions regarding this disclaimer, please contact the NHS GGC MRI physics team on: ggc.MRSafetyExpert@nhs.scot​.

MR Safety policy for Fixed Internal, passive orthopaedic implants

Must read: What this policy does not cover / notable exceptions

This policy does not apply to patients with external fixation devices, a policy for this is covered elsewhere. Note that there are external fixation devices such as the Biomet Ace-Fisher External fixation device and the Stryker Hoffman II external fixation device which are known to be MR Unsafe. Furthermore, this policy does not apply to implants that are not fixed to the bone, for example, stapes implants, a policy for patients with these implants is covered elsewhere. Finally, this policy requires an understanding of the distinction between ‘passive’ and non-invasively expandable orthopaedic (NEO) implants. Only passive orthopaedic implants are covered by this policy. A ‘passive’ orthopaedic implant has no electronic or magnet components, nor does it have its own power source, nor can it be expanded by application of a remote power source. Note that the overwhelming majority of orthopaedic implants will fall into the ‘passive’ category. Conversely, an non-invasively expandable orthopaedic implant is an orthopaedic implant that can be expanded non-invasively by application of a external power source. For more information on non-invasively expandable orthopaedic (NEO) implants, see the information on this page. It is hoped the information provided there will help to you to determine whether a patient implant you are presented with is either passive or a NEO implant. Finally, some Max-Fax patients may have prosthesis held in place by magnetic components such as the Magnacap component and these must be removed prior to scanning.

Must read: What the policy covers

This policy covers patients with orthopaedic implants, entirely fixed within the body (internal) (i.e. implants that are fixed to the bone and where the implant does not extend beyond the skin surface). This policy only covers patients with fixed internal passive orthopaedic implants  i.e. the implant has no electronic or magnetic components and cannot be expanded via application of an external power source. 

Must read: The MR safety policy

General tip: When scanning patients with an orthopaedic implant it is of even greater importance to observe best practice when positioning the patient. That is, the patient should be positioned and insulating pads should be used such as to avoid skin-skin (e.g. thigh to thigh / ankle to ankle) and bore-skin contact points.

NHS GGC policy is that:

i) All patients with fixed internal, passive orthopaedic implants who are conscious and have sensation can be scanned at 1.5T though they should be warned to hit the call button if they experience any heating or discomfort.

ii) Patients with fixed internal, passive orthopaedic implants who are unconscious or lacking in sensation must have risks and benefits considered as a means of justifying their MRI scan.  This will typically be conducted by a Radiologist with help from the MRSE. The following guidance to minimise patient heating should be considered.  Scan at 1.5T rather than 3T, minimise scans and slices to those that are clinically necessary, scan in Normal Operating Mode, remove patient blankets, turn on the in-bore fan.

iii) All patients with fixed internal, passive orthopaedic implants who are conscious and have sensation can be scanned at 3T though they should be warned to hit the call button if they experience any heating or discomfort.

iv) If it is considered clinically necessary to scan a patient who is unconscious or lacking sensation with a fixed internal, passive orthopaedic implant at 3T rather than 1.5T , then a decision as to whether or not to scan the patient must be made by the Radiologist based on a risk/benefit assessment. The MR Safety Expert can advise and to make recommendations to help minimise risks. The following guidance to minimise patient heating should be considered.  Minimise scans and slices to those that are clinically necessary, scan in Implant Mode (or Normal Operating Mode), remove patient blankets, turn on the in-bore fan.

The risk assessment for patients with these implants who are to be scanned under normal circumstances can be found here:

GenericRiskAssessmentForm_fixed_ortho_implants

The risk assessment for patients with these implants who are under sedation or GA can be found here:  

GenericRiskAssessmentForm_fixed_ortho_implants_under_GA

Additional background  information and discussion

The MHRA’s MR Safety Guidelines say in section 4.11.2.1 ‘Patients and volunteers with large metallic implants e.g. hip implants, where heat generation may occur, are not excluded but should be monitored carefully, both in the approach to the magnetic field and during examination. If discomfort is experienced, MR exposure must be discontinued.’

The considerable length of some orthopaedic implants means there is a risk of a resonant antenna effect causing heating, more so at 3T. The policy, relative risks and benefits are discussed below.

General tip: When scanning patients with orthopaedic implant it is of even greater importance to observe best practice when positioning the patient. That is, the patient should be positioned and insulating pads should be used such as to avoid skin-skin (e.g. thigh to thigh / ankle to ankle) and bore-skin contact points.