MR Safety: Bone stimulatorsCan patients with implanted bone growth stimulators be safely scanned?
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Electrical stimulators are used as adjunctive therapy for a variety of orthopedic conditions, especially for accelerating fracture healing and fusion of bone grafts. While most of these devices are entirely external to the patient (and must be removed prior to imaging), a single company (Zimmer BioMet) manufactures the only internally implanted bone growth stimulators — one for the spine and one for the peripheral skeleton.
MR Conditional SpF® Implantable Spinal Fusion Stimulator
The SpF® Implantable Spinal Fusion Stimulator consists of a small direct current generator and two leads with wave- or mesh-shaped terminal platinum cathodes placed directly against raw bone at the fusion site. Bone autograft is then packed on top of the electrodes. At the end of 6 months when the battery is exhausted, the generator and proximal wires are removed. (The distal electrodes will hopefully be encased by bone at that time). The SpF® system is MR Conditional at 1.5T.
The OsteoGen® Bone Growth Stimulator (Zimmer BioMet) has a similar construction to the SpF®, but is intended for peripheral skeletal placement in fracture and fusion sites. Because the manufacturer has not yet certified it for MR use, the OsteoGen® must formally be considered MR Unsafe at present. Due to its great similarity to the SpF®, however, I fully believe this restriction will be lifted within the next few years, and in a pinch, I would have no problem scanning a patient with this device under the same conditions as approved for the SpF®.
The OsteoGen® Bone Growth Stimulator (Zimmer BioMet) has a similar construction to the SpF®, but is intended for peripheral skeletal placement in fracture and fusion sites. Because the manufacturer has not yet certified it for MR use, the OsteoGen® must formally be considered MR Unsafe at present. Due to its great similarity to the SpF®, however, I fully believe this restriction will be lifted within the next few years, and in a pinch, I would have no problem scanning a patient with this device under the same conditions as approved for the SpF®.
References
Chou C-K, McDougall JA, Chan KW. RF heating of implanted spinal fusion stimulator during magnetic resonance imaging. IEEE Trans Biomed Engineering 1997;44:357-373. [DOI LINK]
Shellock FG, Hatfield M, Simon BJ, et al. Implantable spinal fusion stimulator: Assessment of MRI safety. J Magn Reson Imaging 2000;12:214-223. [DOI LINK]
Chou C-K, McDougall JA, Chan KW. RF heating of implanted spinal fusion stimulator during magnetic resonance imaging. IEEE Trans Biomed Engineering 1997;44:357-373. [DOI LINK]
Shellock FG, Hatfield M, Simon BJ, et al. Implantable spinal fusion stimulator: Assessment of MRI safety. J Magn Reson Imaging 2000;12:214-223. [DOI LINK]
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