Hengg Clemens, Mayrhofer Peter, Euler Simon, Wambacher Markus, Blauth Michael, Kralinger Franz
Department of Trauma Surgery and Sports Medicine, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
Unit Geometry and CAD, University of Innsbruck, Technikerstrasse 13, 6020, Innsbruck, Austria.
Arch Orthop Trauma Surg. 2016 Feb;136(2):213-21. doi: 10.1007/s00402-015-2368-6. Epub 2015 Nov 28.
Textbooks commonly recommend using the true anterior-posterior (ap)-view with the patient's arm in a sling and therefore in internal rotation (IR) for radiologic diagnostic assessment of the proximal humerus after trauma. However, IR or external rotation (ER) may affect the projection of the head shaft angle (HSA) and therefore bias the diagnostic conclusion significantly. We hypothesized that neutral rotation (NR) of the arm is mandatory for true ap-view to provide true projection of the HSA.
A simplified geometrical model of the proximal humerus was used to examine the influence of different arm positions and angulations of the central ray in relation to the projection of the HSA.
Both ER and IR misleadingly suggested an increased valgus angle. Simulating the true ap-view with the central ray in cranio-caudal direction, IR changed the projection of the HSA substantially.
In conclusion, standard fixation of the patient's arm in a shoulder sling in IR for true ap-view may result in an oblique projection, potentially leading to incorrect surgical implications. To prevent misdiagnosed valgus or varus angulation, NR of the arm should be obeyed when performing true ap-view X-ray. We, therefore, highly recommend to overcome the traditionally arm position, ensuring the true amount of dislocation to assure correct surgical implications and comparable follow-up examinations.
教科书通常建议在对创伤后近端肱骨进行放射学诊断评估时，使用患者手臂置于吊带中并处于内旋（IR）状态的真正前后位（ap）视图。然而，内旋或外旋（ER）可能会影响头干角（HSA）的投影，从而显著影响诊断结论。我们假设手臂的中立旋转（NR）对于获得真正前后位视图以提供HSA的真实投影是必不可少的。
使用近端肱骨的简化几何模型来研究不同手臂位置和中心线角度对HSA投影的影响。
外旋和内旋均错误地提示外翻角增大。模拟中心线在颅尾方向的真正前后位视图时，内旋显著改变了HSA的投影。
总之，为获得真正前后位视图，将患者手臂以标准方式固定于肩部吊带内并处于内旋状态可能会导致斜位投影，从而可能导致手术判断错误。为防止误诊外翻或内翻成角，在进行真正前后位X线检查时应遵循手臂中立旋转原则。因此，我们强烈建议摒弃传统的手臂位置，确保脱位的真实程度，以保证正确的手术判断和可比的随访检查。
