▶影像征象 | 倒拿破仑帽征 | The inverted Napoleon’s hat sign

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Appearance

The inverted Napoleon’s hat sign is seen on the frontal radiograph of the spine at the level of the fifth lumbar vertebra (L5) and the sacrum (S1). Bone overlying the sacrum simulates the dome of an inverted Napoleon’s hat, with the transverse processes forming the hat’s tapered brim (Figs 1, 2).
倒拿破仑帽征见于脊椎正位片第五腰椎（L5）和骶椎（S1）水平处。与骶椎重叠的骨质与倒置拿破仑帽的圆顶相似，而横突形成了渐缩的边缘。

图1 拿破仑帽

Explanation

Spondylolisthesis is the anterior displacement of one vertebra with respect to another and frequently occurs at the lumbosacral junction. The inverted Napoleon’s
hat sign is produced when a severely subluxed L5 vertebral body (the dome of the hat) projects end-on and overlaps the sacrum.

脊椎滑脱是一个椎体相对于另一个椎体向前脱位，常发生于腰骶关节。当严重的L5椎体（帽子的圆顶）滑脱并重叠于骶椎时，就会产生倒拿破仑帽征。

Notable disruption of any of stabilizing forces may result in depiction of the inverted Napoleon’s hat sign.
任何稳定作用力（韧带、关节等）的显著破坏都可能导致倒拿破仑帽征。

Discussion

Spondylolisthesis at the lumbosacral junction results from a loss of bone stability secondary to congenital defects of the L5 laminae, defects of the pedicles of the L5 inferior articular processes, or defects of the lamina of the sacral superior articular processes.
腰骶关节脊椎滑脱是由于L5椎板先天性缺陷、L5下关节突椎弓根缺陷或骶上关节突椎板缺陷引起的稳定性破坏。

The Newman classification describes the five types of spondylolisthesis: I, congenital or dysplastic; II, isthmic or spondylytic; III, degenerative; IV, traumatic; V, pathologic; and, an additional category established since the original Newman classification, VI, postsurgical.
Newman分类描述了五种类型的脊椎滑脱：I，先天性或发育不良；II，峡部或脊椎裂；III，退变，IV，创伤，V，病理性；以及在最初的Newman分类上另加一类，VI，术后。

Isthmic, degenerative, and postsurgical causes are the most common types.
峡部裂、退变及术后是最常见的类型。

参考文献

  1.Talangbayan L E. The inverted Napoleon's hat sign.[J]. Radiology, 2007, 243(2):603.

2.Eisenberg RL. Atlas of signs in radiology. Philadelphia,Pa: Lippincott, 1984.

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