Article

Magnetic resonance imaging of patients with orthopedic MR Conditional implants

Many Americans end up having implants during their lives. In fact, over one million Americans were discharged from the hospital after having some sort of orthopedic implant procedure in 2011.1 Orthopedic implants include total arthroplasties, as in the knee, hip or shoulder, and implants to stabilize a troublesome joint. The number of implant procedures is increasing, partially due to the aging population and partially due to the number of people who want to stay active as they age.

After joint replacement or repair surgery, patients may have metal screws, plates, or prostheses, which may cause issues when they are having certain procedures and medical imaging studies completed, which may or may not be related to their implant. Because of this, patients should be aware of the type of implant they have. This information could help radiologists and physicians adapt their procedures to the implant.

Types of implants2

  • Screws: Medical screws may be used to tighten up damaged areas and look almost identical to screws used for construction. They are often permanently implanted, because they are used to tighten up damaged areas. Injuries that may be repaired with a screw are numerous, including fractures.
  • Plates: A patient's treatment for fractures, reconstruction and stability may include plates. There are five primary categories for plates: buttress, neutralization, bridging, tension and compression. Each of these types is used for help with healing different types of injuries.
  • Prostheses: Prosthetic implants may replace missing joints or bones or may provide support to a damaged bone. These are commonly used for the knees and hips, as well as the shoulders. The goal is for the patient to regain full range of motion and become pain-free in a short amount of time. These are often implants that are not commonly removed.

Addressing imaging with implants

New technology may help radiologists image patients who have had an implant. Some implants are labeled as MR Conditional, which means they have been validated to be safe under certain conditions with MR imaging. Implants vary with their metal compositions. When patients know what type of implant they have, they provide information for the radiologist about the type of metal in their device.

One acquisition and reconstruction technique is an application that may help radiologists when imaging patients with MR Conditional implants. This techniques is used for soft tissue and bone imaging near MR Conditional devices. This is especially useful for the assessment of bone and tissue around an implant.3 The goal of the technique is to help reduce artifacts caused by metal compared to more conventional MR techniques and to generate diagnostic quality MR images.4

MR multispectral imaging (MSI) is a new technique which, when used with the acquisition and reconstruction technique described above, may enable faster scanning by tailoring the acquisition the patient's specific implant. The less metal, the shorter the scan. Radiologists can also convert these scan time savings into higher resolution images to better depict tissue around the implant.5

The use of orthopedic implants is on the rise and thus the need for MR imaging options to scan this specific patient population may be especially important. Manufacturers and researchers continue to innovate in this clinical area and to collaborate with both orthopedic surgeons and radiologists to identify such opportunities and unmet clinical needs.

References:

  1. Information about Musculoskeletal Procedures and Treatment. aaos.orghttps://www.aaos.org/CustomTemplates/Content.aspx?id=6407. Last accessed October 23, 2019.
  2. Types of Orthopedic Implants. SpectrumOrtho.comhttps://www.spectrumortho.com/2018/03/23/types-of-orthopedic-implants/. Last accessed October 22, 2019.
  3. MAVRIC SL Imaging of Bilateral Hip Prosthesis. SIGNA Pulse of MR. http://www.gesignapulse.com/signapulse/spring_2017/MobilePagedArticle.action?articleId=1160232#articleId1160232. Last accessed October 22, 2019.
  4. MRI of Hip Arthroplasties: Comparison of Isotropic Multiacquisition Variable-Resonance Image Combination Selective (MAVRIC SL) Acquisitions with a Conventional MAVRIC SL Acquisition. AJRhttps://www.ajronline.org/doi/abs/10.2214/AJR.19.21606. Last accessed October 22, 2019.
  5. External calibration of the spectral coverage for three-dimensional multispectral MRI. Magn Reson Medhttps://www.ncbi.nlm.nih.gov/pubmed/26745139. Last accessed October 22, 2019.