Stryker’s Hoffmann 3 external fixator system is an “MR Conditional” device. This means patients with Hoffmann 3 external fixators can be scanned safely in MRI but only under certain conditions laid out by the manufacturer.
These manufacturer conditions are somewhat ambiguous and quite restrictive in regard to the allowable SAR (Specific Absorption Rate – this controls the amount of energy disposition and heating that the patient experiences). While no physical injury has been observed, there have been a number of patients in Hoffmann 3 external fixators who have stopped their scans due to heating.
While we will always aim to scan within the “MR Conditions”, it may not always be possible for the MRI unit to satisfy these parameters whilst achieving the diagnostic quality desired.
With that being the case we may need to scan a patient in this device ‘off-licence’.
We would cite the risk to scanning a patient with this device in an MRI as being low, but to allow us to justify scanning in this way, it would help greatly (and expedite scanning) if you could ensure a detailed summary in the request as to the exact indication for the MRI scan, particularly whilst in the ex-fix.
Similarly, ensuring the surgical note with implant stickers is uploaded to Clinical Portal for review will be of significant benefit as radiographers are required to confirm that only Stryker Apex pins were used in constructing the frame.