目的 分析外伤性肩关节后脱位的影像学表现并探讨其损伤机理。方法 回顾性分析8例外伤性肩关节后脱位患者的 临床表现及其X线平片、MSCT影像特征，讨论肩关节后脱位的发病机理。结果 8例外伤性肩关节后脱位在X线、MSCT 上都具有特征性表现。肩关节正位片显示肱骨头向内旋转，肱骨头关节面与肩胛盂重叠的半月形“泪滴”样影消 失，肱骨头与肩胛盂关系不对称，肱盂关节间隙增宽；腋窝位片显示肱骨头向后脱出。MSCT检查显示肱骨头关节面 朝向肩后，脱离关节盂，肱骨头凹陷性骨折。结论 X线结合MSCT可清晰显示外伤性肩关节后脱位的改变，准确判断 肱骨头脱出旋转方向和程度及其与周围结构的关系，具有重要的临床价值。

Objective To analyze the imaging manifestations of posterior dislocation of shoulder and to explore the mechanism of the injury. Methods The clinical features and imaging characteristics of 8 patients with posterior dislocation of the shoulder were analyzed retrospectively, and the pathogenesis of posterior dislocation of the shoulder was discussed. Results 8 cases of dislocation of the shoulder after X-ray film showing the performance of the hummers, is situated in the first place or function were internal rotation, the hummer large nodule probation, no abnormal joint space, “tear drop” shadow smaller; five patients a result of lateral film thoracic overlapping structure to identify unclear, three lateral humeral head shows that films backward shift. MSCT for the performance of the humeral head spins backwards, away from the limitations of the joints after the mend edge. Conclusion X-ray combined with MSCT can clearly display the change of dislocation of the shoulder joint, to accurately determine the direction of rotation and the humeral head prolapse degree and its relationship with the surrounding structures, it has important clinical value.