000K utf8 1100 2019$c2019-12-02 1500 eng 2050 urn:nbn:de:hbz:464-20191202-134538-2 2051 10.4081/or.2019.8194 3000 Beck, Sascha 3010 Burggraf, Manuel 3010 Busch, André 3010 Landgraeber, Stefan 3010 Martin, Robert J. 3010 Patsalis, Theodor 3010 Wegner, Alexander 4000 Determination of humeral inclination in stemless shoulder arthroplasty using plain radiographs [Beck, Sascha] 4209 Plain radiographs of the shoulder are routinely used to assess implant orientation after shoulder arthroplasty. Recently, humeral inclination has come into focus especially in reverse stemless shoulder arthroplasty. But, in X-ray projections not exactly parallel to the base of the humeral component, the humeral inclination angle cannot be determined precisely. Therefore, we established a mathematical algorithm to calculate the humeral neck shaft angle and counterchecked the formula using plain radiographs of a sawbone model containing a humeral head prosthesis. With increasing angles of retroversion, the base of the humeral component forms an ellipse in plain radiographs. Knowing the width and length of the ellipse as well as the inclination angle in a plain radiograph, the exact inclination angle can be determined using the equation reported below. Thus, independent from the viewing angle or angle of retroversion, the inclination angle of a stemless humeral head implant can be estimated with an accuracy of ±1.5-degree deviation. The algorithm proposed may be the basis for further research on the impact of humeral inclination in stemless shoulder arthroplasty. 4950 https://doi.org/10.4081/or.2019.8194$xR$3Volltext$534 4950 https://nbn-resolving.org/urn:nbn:de:hbz:464-20191202-134538-2$xR$3Volltext$534 4961 https://duepublico2.uni-due.de/receive/duepublico_mods_00070825 5051 610 5550 Humeral inclination 5550 humeral neck shaft angle 5550 reverse shoulder arthroplasty 5550 stemless 5550 total shoulder arthroplasty