Background: 

Surgery for humeral shaft fractures is associated with a high risk of iatrogenic radial nerve palsy (RNP). Plausible causes are difficult anatomical conditions and variants.

Methods: 

We performed a cadaveric study with 23 specimens (13 female and 10 male Caucasian donors) to assess the course and anatomy of the radial nerve (RN) with its branches alongside the humeral shaft. The accuracy of identification of the RN in the surgical field was analyzed by measuring the location, course, diameter, and form of each nerve and vessel of interest.

Results: 

The RN is not a single structure running alongside the humeral shaft; at least 4 parallel structures crossed the dorsal humerus in all subjects. The RN was accompanied by 2 vessels and at least 1 other nerve, which we named the musculocutaneous branch (MCB). With an oval profile and an average diameter of 3.1 mm (range, 2.6 to 3.8 mm), the MCB was thinner but, in some cases, close to the average diameter of 4.7 mm (range, 4.0 to 5.2 mm) of the RN, which had a round profile. Both accompanying vessels had similar diameters: 3.5 mm (range, 2.6 to 4.2 mm) for the radial collateral artery and 4.0 mm (range, 2.9 to 4.4 mm) for the medial collateral artery. In 20 (87%) of the cases, the RN ran proximal to and in 3 (13%) of the cases, distal to the MCB. Furthermore, a distal safe zone of at least 110 mm (range, 110 to 160 mm) was found, measured from the radial (lateral) epicondyle proximally.

Conclusions: 

The RN does not cross the dorsal humerus alone, as often stated in anatomical textbooks, but runs parallel to vessels and at least 1 nerve branch with a similar appearance. Thus, for reliable preservation of the RN, we recommend identification and protection of all crossing structures in posterior humeral surgeries 110 mm proximal to the radial epicondyle.

中文翻译：

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肱骨背侧桡神经的外科解剖：尸体研究

背景： 

肱骨干骨折手术与医源性桡神经麻痹（RNP）的高风险相关。可能的原因是困难的解剖条件和变异。

方法： 

我们对 23 名样本（13 名女性和 10 名男性白种人供体）进行了尸体研究，以评估桡神经 (RN) 及其沿肱骨干的分支的走行和解剖结构。通过测量每条感兴趣的神经和血管的位置、路线、直径和形式来分析手术野中 RN 识别的准确性。

结果： 

RN不是沿着肱骨干的单一结构；在所有受试者中，至少有 4 个平行结构穿过肱骨背侧。RN 伴有 2 条血管和至少 1 条其他神经，我们将其命名为肌皮支 (MCB)。MCB 具有椭圆形轮廓和 3.1 毫米（范围，2.6 至 3.8 毫米）的平均直径，更薄，但在某些情况下，接近 RN 的 4.7 毫米（范围，4.0 至 5.2 毫米）的平均直径，它有一个圆形的轮廓。两条伴随血管的直径相似：桡侧副动脉直径为 3.5 毫米（范围，2.6 至 4.2 毫米），内侧侧支动脉直径为 4.0 毫米（范围，2.9 至 4.4 毫米）。在 20 例 (87%) 的病例中，RN 在 MCB 的近端和 3 例 (13%) 的病例中位于 MCB 的远端。此外，发现了至少 110 毫米（范围，110 至 160 毫米）的远端安全区，

结论： 

RN 并不像解剖教科书中经常提到的那样单独穿过肱骨背侧，而是平行于血管和至少 1 个外观相似的神经分支。因此，为了可靠地保存 RN，我们建议识别和保护肱骨后部手术中距离桡骨上髁近 110 mm 处的所有交叉结构。