Introduction: Recently, isocentric C-arm fluoroscopy (Iso-C 3D) has been introduced as a precise imaging modality for intraoperative evaluation and management of fractures and osteosyntheses. The Siemens Iso-C 3D collects multiple fluoroscopic images during a 190-degree arc of rotation around the anatomic region of interest and reconstructs them into sagittal, axial, and coronal planes. Like the Iso-C 3D, the new Ziehm Vario 3D imaging system reconstructs images in multiple planes, but only requires a 136-degree arc of rotation. The purpose of this study was to compare the image quality and range of applicability of these two imaging systems.
Methods: All the tests were performed on a human cadaver. In the first part of the experiment, different bones and joints were scanned in their native condition using both the Iso-C 3D and Vario 3D. In the second part of the experiment, scans were performed in the same anatomic regions after simulated fractures and subsequent fixation. In some cases, suboptimal placement of hardware was intentionally undertaken. Direct visualization of the fracture construct and in certain cases computed tomographic (CT) imaging served as the gold standard. The scans from both imaging systems were analyzed using a DICOM viewer by five orthopedic trauma surgeons randomized and blinded to the study. The evaluation was based on the overall image quality, delineation of cancellous and cortical bone, delineation of joint surfaces, presence of artifacts, visualization quality of intra-articular incongruities, quality of reduction and implant positioning, and clinical applicability of the scan. These items were rated using a visual analog scale and a points system. A total of 55 3D scans were made and evaluated.
Results: There was no significant difference between the two imaging systems in terms of the overall image quality, delineation of cancellous and cortical bone, and the presence of artifacts. The delineation of joint surfaces was significantly better visualized with the Iso-C 3D. Furthermore, Iso-C 3D scans demonstrated a higher overall clinical applicability than Vario 3D images. However, the Vario 3D was able to provide superior quality with scans of the shoulder joint and the adipose tissue. There was no significant difference in the visualization of intra-articular incongruities, quality of reduction, and implant positioning.
Conclusion: Although the Iso-C 3D imaging system was superior in delineating the joint surfaces, the image quality, and the overall clinical applicability, the study revealed that both devices provided 3D images with sufficient quality to the surgeon to assess clinically relevant questions, including the quality of fracture reduction and implant positioning. On the other hand, the Ziehm Vario 3D is capable of doing scans of the shoulder area, which could not be taken with the Siemens Iso-C 3D because of the isocentric design.