[The isocentric C-arm. Visualization of fracture reduction and screw position in the radius]

In addition to conventional C-arms which can be used for intraoperative imaging, C-arm image amplifiers with an option for three-dimensional imaging (ISO-C3D) are available to visualize reduction of fragments and positions of implants. In ten cadaver wrists intra-articular steps and intra-articular screw positions were simulated. Images obtained by conventional two-dimensional C-arm image amplifier, computed tomography and ISO-C3D were evaluated by four investigators using a questionnaire. For 2D image amplifier scans the investigators rated the quantity of the articular steps correctly in 45%, incorrectly in 51% and were uncertain in 4%. Concerning CT scans these values were 57, 40 and 3%, respectively. With a slow 190° ISO-C3D mode the investigators rated the steps correctly in 47%, incorrectly in 44% and were uncertain in 9%. The positions of the tip of the screw were rated correctly for 2D scans in 56%, incorrectly in 40% and were uncertain in 4%. For CT screw positions were assessed correctly in 40%, incorrectly in 43% and were uncertain in 17%. For ISO-C3D in fast 190° mode the rating was correct in 59%, wrong in 30% and uncertain in 11%. In the slow Iso-C3D mode the results were inferior with correct assessment in 51%, wrong results in 36% and uncertain evaluation in 13%. In our cadaveric study, ISO-C3D scans have been found valuable for intraoperative controls of implant positions and assessment of intra-articular steps.