How Metal Implants Distort CT Numbers in Dogs: New 2025 Cadaver Study Insights

Effects of Metal Implants on Computed Tomographic Attenuation Values in the Canine Antebrachium: A Cadaveric Study

Giulia Dalla Serra, Marie-Pauline Maurin, Cliona Skelly, Irene Hernandez-Girón, Séamus Hoey

Background

Computed tomography (CT) is frequently used to assess postoperative orthopedic patients because it overcomes the limitations of radiography, particularly in evaluating bone healing, implant positioning, and complications. However, metallic implants generate artifacts—such as streaking from beam hardening and photon starvation—that distort the appearance and attenuation values of adjacent tissues. While the phenomenon is well studied in human medicine, comparable data in veterinary patients is scarce. This study aimed to determine how stainless steel (316L) orthopedic implants affect CT attenuation values of nearby skeletal and soft-tissue structures in the canine antebrachium.

Methods

This prospective ex vivo study used 20 forelimbs from 10 adult Greyhound cadavers. CT scans were acquired before and after surgical placement of a stainless-steel 9-hole locking compression plate with four bicortical screws on the cranial radius. Standardized scanning parameters and reconstruction algorithms were used for all limbs in both phases. Five transverse slices were selected per limb, representing locations at and proximal to the implant. Four ovoid regions of interest (ROI)—cranial cortex, radial medulla, caudal cortex, and caudal soft tissues—were measured on each slice. Linear mixed modeling, with post hoc testing and false-discovery rate correction, assessed differences in Hounsfield units (HU) between pre- and post-implant scans.

Results

Significant HU increases after implant placement were observed in the cranial cortex, radial medulla, and caudal cortex at Sites 2 and 3 (locations directly adjacent to the plate). At Site 1, the cranial cortex showed a significant decrease in HU, while other tissues at that site showed no significant differences. No significant HU changes were observed at Sites 4 or 5, which were 1–3 cm proximal to the implant. Caudal soft tissues showed no significant changes at any site. The results demonstrate that metal implants substantially alter CT attenuation values of adjacent cortical and medullary bone.

Limitations

As a cadaveric study, freeze–thaw effects may have influenced tissue density, and the results might not fully extrapolate to living patients. Only one implant type (316L stainless steel) and geometry were tested, limiting generalizability to other materials or designs. The soft-tissue ROI were positioned farther from the implant, which may have reduced sensitivity to soft-tissue artifact effects. MAR (metal artifact reduction) techniques were not used to establish a baseline, but this choice prevents assessment of how such techniques might have mitigated distortion.

Conclusions

Stainless steel orthopedic implants significantly distort CT attenuation values in adjacent bone, producing both artificially increased and decreased HU depending on location relative to the implant. These alterations can impair diagnostic confidence and lead to potential misinterpretations when evaluating bone healing or pathology near metal hardware. The study establishes baseline artifact effects in canine limbs and provides a foundation for future research on metal artifact reduction methods in veterinary imaging

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