A new method to locate the radial head "safe zone" on computed tomography axial views.
PURPOSE
Direct location of the "safe zone" on a CT axial view is impossible because the radial head is circular in shape. Previous "safe zone" location methods are not appropriate if the physician is unable to visualize the actual radial head. This study aims to introduce a new method to locate the "safe zone" on CT.


METHODS
CT scans were performed on 20 intact cadaveric upper limbs from 20 different corpses in full pronation and supination. The DICOM-format raw data were then re-sliced and analyzed in Mimics 17.0 (Materialise, Belgium). The radial interosseous border (IB) is shaped like a droplet on the axial view; its axis was selected as our reference line (RL). A parallel line in the radial head axial slice was created, and its position relative to the "safe zone" was studied. Deviation in RL direction was evaluated.


RESULTS
Safe-zone scope was 114.41°±11.99. The rotation angle from the RL to the safe-zone's anterior and posterior border was 215.03°±5.99 and 100.62°±8.12, respectively. Rotation direction (clockwise or anti-clockwise) depended on relative radius-ulna position. The safe zone was located by determining these two borders. The reference line's direction was stable in the upper half of the IB; its distance to the radial head fovea was 77.33° mm±6.24.


CONCLUSIONS
The radial head "safe zone" can be located on CT axial view based on the upper half of the IB using this new method. The method is clinically applicable to determine whether postoperative elbow malrotation results from plate impingement.
['Zhan|Y|Y|', 'Luo|C F|CF|', 'Chen|Y J|YJ|']
D059925:Anatomic Landmarks D002102:Cadaver D004838:Epiphyses D006801:Humans D007091:Image Processing, Computer-Assisted D011403:Pronation D011884:Radius D011885:Radius Fractures D012399:Rotation D013484:Supination D014057:Tomography, X-Ray Computed
Location Radial head Safe zone CT