Three-Dimensional Fluoroscopy For Evaluation of Articular Reduction and Screw Placement in Calcaneal Fractures

Abstract

Anatomic reconstruction of the posterior calcaneal facet after intra-articular fracture is one of the critical factors in achieving a good functional result. Intraoperative evaluation of fracture reduction and implant placement relies on direct view by standard fluoroscopy. We hypothesized that three-dimensional (3D) fluoroscopy is more accurate than conventional fluoroscopy, and equivalent to CT for determining fracture reduction and screw position in calcaneal fractures. A Sanders type IIB fracture pattern was created in eight embalmed lower extremity cadaver specimens. First, the posterior facet was reduced with a step-off of 0 mm to 2 mm in 0.5-mm increments. All specimens had two dimensional (2D) fluoroscopy, 3D fluoroscopy with an Iso-C3D, and a CT scan. Next, screws were placed so they protruded into the subtalar and calcaneocuboid joint and through the medial wall. All specimens were imaged again. Three observers evaluated all imaging studies, and the sensitivities and specificities of each modality were determined. Both the Iso-C3D and the CT were more specific for anatomic reduction (75% and 100%, respectively) than fluoroscopy (62%). For the malreduced trials, the Iso-C3D and CT were both 100% sensitive, and the sensitivity of fluoroscopy was 63% (p < 0.001 for both). For the intra-articular screws, the Iso-C3D and CT were accurate in all cases (sensitivities = 100%), and fluoroscopy was accurate in five of the eight trials for both joints (sensitivities = 63%). Finally, with screws protruding through the medial wall, the sensitivity of fluoroscopy was 25%, for the Iso-C3D 88% (p = 0.02), and for CT was 100% (p = 0.003). Three-dimensional fluoroscopic imaging is more accurate than 2D fluoroscopy for detection of intra-articular incongruities and implant position and is similar to CT. This new technology may be particularly useful in assessing calcaneal fractures and may lead to improved fracture reduction, less implant misplacement, and improved patient outcomes.