INTRODUCTION Numerous publications have studied the regional anatomy of the carpal tunnel to define a "safe zone" to reduce the risk of perioperative neurovascular complications. This zone, located between the ulnar neurovascular bundle and the median nerve, is considered to be safe mainly because of the absence of vascular structures. This study aims to assess the presence of arterioles within this area using superb microvascular imaging (SMI). MATERIALS AND METHODS The images from patients who underwent a bilateral routine wrist ultrasound with SMI, between January 28 and February 28, 2019, were retrospectively reviewed by two radiologists to evaluate the presence and location of arterioles in the safe zone. In addition, cadaveric wrists injected with intra-arterial red latex underwent dissection of the carpal tunnel. RESULTS The images from 27 patients (54 wrists) were reviewed. In the safe zone, arterioles were seen superficial to the retinaculum in 36 wrists (36/54; 66.7%) and deep to the retinaculum in 21 wrists (21/54; 38.9%). The arterioles located deep to the retinaculum were more frequently found close to the median nerve (21/54; 38.9%) than to the ulnar artery (9/54; 16.7%). In five cadaveric wrists, arterioles were detected superficial to the retinaculum in 3 wrists (3/5; 60%) and deep to the retinaculum in 2 wrists (2/5; 40%). CONCLUSION Arterioles can be seen in the safe zone both superficial and deep to the flexor retinaculum. Deep to the retinaculum, they are mainly observed in the proximal aspect of the carpal tunnel and more frequently close to the median nerve. KEY POINTS • Superb microvascular imaging (SMI) enables the visualization of arterioles within the "safe zone" of the carpal tunnel (visible both superficial and deep to the flexor retinaculum). • Arterioles were more frequently observed in the proximal aspect of the carpal tunnel. • Deep to the retinaculum, arterioles were more frequently seen in proximity to the median nerve.

中文翻译：

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腕管超声检查：正中神经尺侧的“安全区”真的没有血管吗？

引言许多出版物已经研究了腕管的局部解剖学，以定义一个“安全区”以减少围手术期神经血管并发症的风险。位于尺神经血管束和正中神经之间的该区域被认为是安全的，主要是因为没有血管结构。这项研究旨在使用出色的微血管成像（SMI）评估该区域内小动脉的存在。材料和方法2019年1月28日至2019年2月28日期间，接受SMI例行双侧手腕超声检查的患者的图像由两名放射科医生回顾性评估，以评估安全区内小动脉的存在和位置。此外，注射了动脉内红色乳胶的尸体手腕进行了腕管解剖。结果回顾了27例患者（54腕）的图像。在安全区域，在36个腕部中发现小动脉位于视网膜浅层（36/54; 66.7％），而在21个腕部中的视网膜深处可见小动脉（21/54; 38.9％）。位于视网膜深处的小动脉比靠近尺动脉（9/54； 16.7％）更靠近正中神经（21/54； 38.9％）。在5个尸体腕部中，在3个腕部中检测到了视网膜的小动脉（3/5； 60％），在2个腕部中检测到了视网膜的深处（2/5; 40％）。结论在安全区浅层和深部屈肌腱膜均可见小动脉。它们位于视网膜深处，主要在腕管的近端观察到，更常见于正中神经附近。要点•出色的微血管成像（SMI）使可视化腕管“安全区”内的小动脉（在屈肌视网膜的表浅和深处均可见）。•在腕管的近端更经常观察到小动脉。•在视网膜深处，在正中神经附近更经常看到小动脉。