Spinal and Orthopedic Biomedical Implant Compatibility with 7 Tesla Magnetic Resonance Imaging: A Scoping Review

Introduction: The usage of 7 Tesla (T) magnetic resonance imaging (MRI) is expanding across spinal and orthopedic surgical specialties. However, few biomedical implants have been tested for compatibility with 7T MRI, limiting its use in patients with implants. Implant compatibility at 7T can be determined via American Society for Testing Materials (ASTM) International guidelines. Our systematic review seeks to summarize all spinal and orthopedic implants that have been tested for compatibility with 7T MRI.

Methods: A systematic search was performed using PubMed, MEDLINE, Web of Knowledge, and citation matching. Studies written in English that included at least one orthopedic surgery implant and at least one safety outcome were included. Study inclusion, quality, and risk of bias was independently assessed by two authors. Data was extracted for the implant(s) studied, implant composition, phantom composition, deflection angle, torque, temperature change, and ASTM International guideline application.

Results: Overall, four studies consisting of 48 unique orthopedic implants were included. Implants included were plates, pedicle screws, cables, staples, spinal rods, intramedullary nails, cross-linking bridges, and total joint replacement components. Outcomes of this review suggest 45 of the 48 individually tested orthopedic implants are likely compatible for 7T MR imaging based on limited radiofrequency-induced temperature increases, deflection angle, and torque data. Three of the 48 individual implants demonstrated variable safety results.

Conclusion : We identified several implants that are likely compatible with 7T MRI. At this time, caution must still be taken when imaging all implants, especially those with quantitative results that are not within the established compatibility ranges.