Background

The sural nerve (SN) is a cutaneous sensory nerve innervating the posterolateral leg. The SN is formed from a highly variable set of contributing nerves called the sural nerve complex (SNC). The SNC is made up of the lateral sural cutaneous nerve, medial sural cutaneous nerve, sural communicating branch, and SN. The SN is frequently cited as the most common donor nerve graft and is commonly injured in procedures of the lower extremity. Recent meta-analysis standardized six morphologies of the SNC and established a required reporting criterion for the group of nerves forming the SN. Due to the inconsistencies in previous literature, this study will group observed SNC's by one of these six SNC morphologies to assess and validate the meta-analysis grouping criteria. This study will also collect the same morphometric data previously outlined in order to grow the number of samples that are reported in a standardized fashion.

Methods

100 formalin and 4 Theil preserved cadavers (n = 208) lower limbs were bilaterally dissected at Kansas City University and Creighton University School of Dentistry to observe the SNC in its entirety on the posterolateral leg. Anatomic data was captured utilizing the standardized morphologies types 1–6 with two sub-typing. Nerves that were found to be outside of this categorization were placed in an unassigned grouping.

Results

The most prevalent SNCs were type 1 at 41.35% (n = 86) and type 3 nerves at 34.62% (n = 72). Type 2 was found 8.65% (n = 18), type 4 and 5 were found each at 0.48% (n = 1). Type 6 was not observed. When comparing the present studies frequency of nerve types 1–6 to the meta-analysis a sub-grouping of “North American” cadaveric studies a X² = .903 p = .030 was found. Two distinct and previously unassigned formations of the SNC were 10.58% (n = 20) and 3.85% (n = 8) of data. These two SNC are termed type 7 & 8, these represent two formations of SN that are outside of what was previously reported. 15.87% (n = 33) did not match visual descriptions based on nerve origin of a type 1 SNC but met written definitions. These were termed type 1A1 and type 1A2. The SNC was asymmetrical in 57.69% (n = 120). The pooled mean length of the SN was 32.97 ± 14.12 cm (31.05–34.88), mean diameter was 2.31 ± 0.83 mm (2.20–2.42, and the distance of the posterior border of the lateral malleolus to the SN was found to be 1.72 ± 0.70 cm (1.63–1.80).

Conclusion

Anatomic variation in the SNC is highly variable, yet is consistent with previously observed literature. This study demonstrates two unaccounted formations of the SNC as well as two additional subcategories of SNC that were not included in the previous meta-analysis. These four variants warrant inclusion as standard formations of the SNC due to the high prevalence observed in this study as well as historical consistency observed in previous literature and case reports. These two SNC formations increase the risk of iatrogenic injury during surgical interventions of the lower extremity. Morphometric data describing the spatial relationship of this nerve complex on the posterolateral leg is consistent with previously reported data and aids in generating a large data set for future studies to characterize spatial properties of this nerve complex.

中文翻译：

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腓肠神经复合体的解剖：未解释的解剖变异和形态测量数据

背景

腓肠神经 (SN) 是一种支配后外侧腿的皮感觉神经。SN 由一组高度可变的神经组成，称为腓肠神经复合体 (SNC)。SNC由腓肠外侧皮神经、腓肠内侧皮神经、腓肠交通支和SN组成。SN 经常被引用为最常见的供体神经移植物，并且通常在下肢手术中受伤。最近的荟萃分析标准化了 SNC 的六种形态，并为形成 SN 的神经组建立了所需的报告标准。由于先前文献中的不一致，本研究将通过这六种 SNC 形态之一对观察到的 SNC 进行分组，以评估和验证荟萃分析分组标准。

方法

100 具福尔马林和 4 具 Theil 保存的尸体 (n = 208) 下肢在堪萨斯城市大学和克赖顿大学牙科学院进行双侧解剖，以观察后外侧腿上的整个 SNC。使用具有两个子类型的标准化形态类型 1-6 捕获解剖数据。发现不在此分类范围内的神经被置于未分配的分组中。

结果

最普遍的 SNC 是 41.35% (n = 86) 的 1 型和 34.62% (n = 72) 的 3 型神经。发现类型 2 为 8.65% (n = 18)，发现类型 4 和 5 各为 0.48% (n = 1)。未观察到类型 6。当将当前神经类型 1-6 的研究频率与荟萃分析进行比较时，“北美”尸体研究的亚组 a X ²= .903 p = .030 被发现。SNC 的两个不同且以前未分配的编队分别占数据的 10.58% (n = 20) 和 3.85% (n = 8)。这两个 SNC 被称为 7 型和 8 型，它们代表了先前报道之外的两种 SN 形成。15.87% (n = 33) 不符合基于 1 型 SNC 神经起源的视觉描述，但符合书面定义。这些被称为1A1型和1A2型。SNC 不对称性为 57.69% (n = 120)。SN 的合并平均长度为 32.97 ± 14.12 cm (31.05–34.88)，平均直径为 2.31 ± 0.83 mm (2.20–2.42，外踝后缘到 SN 的距离为 1.72 ± 0.70 厘米（1.63–1.80）。

结论

SNC 的解剖变异是高度可变的，但与先前观察到的文献一致。这项研究证明了 SNC 的两个未解释的形成以及之前的荟萃分析中未包括的两个额外的 SNC 子类别。由于本研究中观察到的高患病率以及先前文献和病例报告中观察到的历史一致性，这四种变体值得作为 SNC 的标准形式。这两种 SNC 结构增加了下肢手术干预期间医源性损伤的风险。描述该神经复合体在后外侧腿上的空间关系的形态测量数据与先前报道的数据一致，并有助于为未来研究生成一个大型数据集，以表征该神经复合体的空间特性。