Department of Anatomy, Faculty of Medicine, Tottori University, 86 Nishi-cho, Yonago, 683-8503, Japan.
Department of Anatomy, Kochi Medical School, Kochi University, Nankoku, Japan.
Anat Sci Int. 2024 Jun;99(3):326-330. doi: 10.1007/s12565-024-00776-4. Epub 2024 May 11.
The extensor digitorum profundus complex underwent degeneration of the ulnar segments during primate adaptation and evolution. This process resulted in the preservation of only the extensor pollicis longus and extensor indicis in some apes, including humans. Consequently, anatomical variations within the digitorum profundus complex in modern humans have been well-documented, with detailed reports on their frequency and patterns in previous studies. Here, we report an unusual arrangement involving two anomalies in the extensor digitorum profundus complex, identified in a 66-year-old Japanese male cadaver. In this cadaver, two accessory muscles differentiated from both the extensor pollicis longus and extensor indicis. Notably, the latter muscle featured a tendon bifurcating towards both the thumb and index fingers, referred to as the extensor pollicis et indicis communis. Under the extensor retinaculum, the tendon of the accessory extensor pollicis longus passed through an independent compartment, whereas that of the extensor pollicis et indicis communis traversed a compartment shared by the extensor indicis and the extensor digitorum communis. Both muscles were innervated by the posterior interosseous nerve. Previous studies have reported that the accessory slip of the extensor pollicis longus and extensor pollicis et indicis communis appear at frequencies of 0.6% and 0.4-1.4%, respectively. However, to the best of our knowledge, a configuration in which both appear simultaneously has not been reported. The data from this case could provide essential insights into the variations in the extensor digitorum profundus complex in humans and non-human primates.
在灵长类动物的适应和进化过程中，伸指深肌复合体的尺侧部分发生了退化。这一过程导致只有拇长伸肌和示指伸肌在一些猿类中得以保留，包括人类。因此，现代人类伸指深肌复合体的解剖变异已经得到了很好的记录，之前的研究详细报道了它们的频率和模式。在这里，我们报告了一个不寻常的排列，涉及伸指深肌复合体中的两个异常，在一个 66 岁的日本男性尸体中发现。在这个尸体中，有两个从拇长伸肌和示指伸肌分化而来的副肌。值得注意的是，后者的肌肉有一个肌腱分叉到拇指和食指，称为拇示指固有伸肌。在伸肌支持带下方，副拇长伸肌腱通过一个独立的间隔，而拇示指固有伸肌腱穿过一个由示指伸肌和指总伸肌共享的间隔。这两块肌肉都由骨间后神经支配。之前的研究报告称，拇长伸肌和拇示指固有伸肌的副腱出现的频率分别为 0.6%和 0.4-1.4%。然而，据我们所知，同时出现这两种情况的配置尚未有报道。这个病例的数据可以为人类和非人类灵长类动物伸指深肌复合体的变异提供重要的见解。
