The Hoffmann 3 is an MR Conditional device. This means patients with this device can be safely scanned in MRI but under certain conditions. The manufacturer conditions are somewhat ambiguous and quite restrictive in regard to the allowable specific absorption rate (SAR) which controls the amount of energy disposition and heating that the patient experiences. While no physical injury has been observed we have now had a number of patients with this device who have stopped their MR 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 conditions and also get the diagnostic quality desired. We would consider the risk to a patient with this device to be low. Referrals for scanning a patient with this device should be vetted by a radiologist to ensure the benefit of scanning a patient with this device with MRI outweighs the risk. Guidance for radiologists vetting these queries can be found here.
Given that the patient referral will have been vetted, what follows is guidance for radiographers in order to:
1. Confirm the patient has a Hoffmann 3 device with only Hoffmann 3 MR Conditional components and that you satisfy yourself that these components are non-ferrous. Complete the Checklist for Radiographers which can be found here. A poster from Stryker listing MR Conditional Hoffmann 3 components and MR Unsafe Standard Hoffmann 2 components may be also useful, it can be found here. A list of MR Conditional Stryker Apex pin part numbers can be found on the attached pdf here. While this is quite an old document, this does look to be a comprehensive list of model types and also states that all Stryker Apex pins are ‘MR safe’, though they really mean MR conditional. In brief, provided the APEX pins are Stryker pins, the they are ok for MR.
2. Adjust and monitor SAR levels to satisfy the MR Conditions. Refer to the guide for managing SAR on the Siemens Aera which can be found here.