From the Guidelines
Both a dental retainer in the mouth and a nail used in ankle fracture repair are considered metallic objects that can potentially interfere with MRI procedures, and it is crucial to inform the MRI technologist and radiologist about these implants before the scan. When considering the safety of these implants in the context of an MRI, it's essential to differentiate between their potential impact. Dental retainers, being removable, should be taken out before the MRI to prevent image distortion and potential heating, as noted in guidelines that emphasize the removal of any metallic items, such as dental prostheses, jewelry, and clothing with zippers or buttons, to ensure safety and image quality 1.
For the ankle nail, the situation is more complex. Most modern orthopedic implants used for fracture fixation are made of MRI-compatible materials like titanium or titanium alloys, which are generally safe for MRI, according to the principle that the specific type, location, and material of the implant must be known before scheduling an MRI examination 1. However, the specific composition of the implant matters significantly, as it determines whether the implant is MRI-safe, MRI-conditional (safe under certain conditions), or MRI-unsafe. Even MRI-compatible metals can cause local image distortion around the implant area, potentially affecting image quality near the ankle.
To ensure safety, it is standard practice to request the patient's implant pass and check with the implant/device manufacturer to determine the implant's safety level, categorizing them into "MRI unsafe" (an absolute contraindication), among other categories 1. For safety reasons, providing documentation about the ankle implant, including when it was placed and the specific type of hardware used, is likely necessary. This approach aligns with guidelines that recommend prescreening patients for potentially relevant MRI contraindications using a standardized checklist, which includes implants and metallic objects 1.
From the Research
Metallic Objects in MRI
- A retainer in the mouth can be considered a metallic object for an MRI, as studies have shown that certain types of retainers can cause artifacts in MRI scans 2, 3.
- The type of retainer and its location can affect the likelihood of artifacts, with stainless steel retainers causing more distortion than titanium or ceramic retainers 2.
- However, not all retainers need to be removed before an MRI scan, and the decision to remove a retainer should be based on the specific area of investigation and the type of retainer 2, 3.
Ankle Fractures and MRI
- Ankle fractures, including those treated with nails or plates, can also be a consideration for MRI scans 4, 5, 6.
- However, there is limited information available on the specific interaction between ankle fracture hardware and MRI scans.
- It is likely that the hardware used to treat an ankle fracture, such as a nail or plate, would be considered a metallic object for an MRI, but the extent to which it would cause artifacts or interfere with the scan would depend on various factors, including the type of hardware and the location of the fracture.
Interaction between Retainer and Ankle Fracture Hardware in MRI
- There is no direct evidence available on the interaction between a retainer in the mouth and ankle fracture hardware in an MRI scan.
- However, it is likely that both the retainer and the ankle fracture hardware would be considered metallic objects for an MRI, and their presence could potentially cause artifacts or interfere with the scan 2, 3, 4, 5, 6.