Photon-Counting Detector CT for Imaging Around Orthopedic and Spinal Metallic Implants: A Systematic Review

Metallic orthopedic and spinal implants degrade computed tomography (CT) image quality through beam hardening, photon starvation, and scatter artifacts that can obscure adjacent bone and soft tissue. Photon-counting detector CT (PCD-CT) provides intrinsic spectral data, electronic noise suppression, ultra-high spatial resolution, and high geometric dose efficiency, features that are theoretically well suited to imaging around metal. No systematic review has compared PCD-CT with energy-integrating detector CT (EID-CT) in this setting. PubMed/MEDLINE, Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science Core Collection, and Scopus were searched on August 2, 2026, without language, date, or study-design restrictions. Eligible studies directly compared PCD-CT with EID-CT in the presence of metallic orthopedic or spinal implants in clinical, cadaveric, ex vivo, or phantom settings and reported outcomes related to image quality, metal artifacts, bone or implant-interface visualization, diagnostic confidence, image noise, or radiation dose. PCD-CT consistently reduced image noise and increased signal-to-noise and contrast-to-noise ratios in three of three studies and reduced radiation dose by approximately 45%-50% at comparable image quality in two of two direct comparisons. Bone and bone-implant interface visualization generally favored PCD-CT in three of four studies. Metal-artifact reduction was conditional: PCD-CT outperformed EID-CT when high-kiloelectron-volt (keV) virtual monoenergetic imaging (VMI), with or without iterative metal-artifact reduction (iMAR) and tin filtration, was applied, whereas PCD-CT polyenergetic images were not consistently superior and occasionally demonstrated greater streak artifacts than EID-CT. When combined with spectral post-processing, PCD-CT matches or exceeds EID-CT for imaging adjacent to orthopedic and spinal metal while approximately halving radiation dose. However, the evidence base is small and heterogeneous, and larger paired clinical studies using standardized, objective outcomes are needed.