A Tale of Twos: Dual-energy CT, an Indispensable Metal Artifact Reduction Tool Around Implants: A Multi-center Experience from Two Primary and Revision Hip Arthroplasty Units

Purpose: To evaluate the added role of dual-energy computed tomography (DECT) in the detection and visualization of periprosthetic complications around metal implants in the pelvis and hip in the United Kingdom and the United States.

Methods and Materials: Adult patients with equivocal radiographic findings on plain radiographs were referred for DECT imaging. Comparison between the standard images at 140 KeV, extrapolated virtual monoenergetic images, at 90 KeV, 120 KeV, 160 KeV, and 190 KeV, evaluation of images using 2-, 5-, 8-, and 10-mm slabs, and the use of iterative metal artifact reduction and iterative beam-hardening correction reconstruction algorithms was performed. The images were acquired on Siemens SOMATOM Force scanners, and the postprocessing image analysis was performed on Syngo.via and Sectra PACs. All patients were discussed in weekly multidisciplinary meetings in either institution (medical decision making [MDMs]). Patient outcomes and management were recorded and analyzed independently.

Results: Complications detected around total hip arthroplasties (THAs) include fractures, nonunion, bony abnormalities, implant failure (including dislocation, polyethylene wear and loosening, implant fracture, infection, aseptic lymphocytic vasculitis associated lesion debris), implant-associated synovitis, and other soft tissue abnormalities including abscesses, hematoma, collection, muscle atrophy, and/or tendon attrition. DECT is a relatively new technique in musculoskeletal imaging. In our presentation we discuss and explain common artifacts related to CT imaging around metal implants, with basic and advanced tools to minimize them, with a particular focus on the added value of DECT in this growing cohort of patients. DECT demonstrated a significant improvement in the visualization and accuracy in the assessment of the extent of these complications. Metal artifact reduction is particularly useful in this elderly population with osteopenia/osteoporosis. Images used for three-dimensional (3D) printing allowed for more dependence on automated analysis, with less input from radiologists, reducing the costs of analysis time. This offered more cost-effective prints to plan revision surgery. DECT offered 3D cinematic rendering evaluations that enhanced the reliability and satisfaction with the diagnosis and facilitated MDM discussions. DECT demonstrated improved visualization of osteopenic or osteoporotic bone with enhanced image quality for bone, soft tissues, and bone–metal interfaces. We can now image dose effectiveness at lower or equal doses with improved diagnostic quality of the final scans.

Conclusion: Improvements in implant design and surgical techniques, evidence for improved outcomes with earlier interventions, and increased life expectancy has created a growing population of patients with metalwork. THA, in particular, is in high demand, with estimated exponential growth rates (> 500,000 in the United States; 325,000 a year in the United Kingdom by 2030 according to the respective national registry databases). The demands on pre- and postoperative imaging are therefore likely to mirror this growth. New techniques including DECT show promising results and are likely to be more widely incorporated into routine standards of care.