Sakanaka Koichiro, Yamamoto Masahito, Hirouchi Hidetomo, Kim Ji Hyun, Murakami Gen, Rodríguez Vázquez José Francisco, Abe Shin-Ichi
Department of Anatomy, Tokyo Dental College, Tokyo, Japan.
Department of Anatomy, Chonbuk National University School of Medicine, Jeonju, Korea.
Anat Cell Biol. 2019 Dec;52(4):436-442. doi: 10.5115/acb.19.128. Epub 2019 Dec 31.
During observations of mid-term and late-stage fetuses, we found a joint disk-like structure at the anterior component of the median atlanto-axial joint. At mid-term, the disk-like structure was thick (0.1-0.15 mm) relative to the sizes of bones surrounding the joint. However, it did not completely separate the joint cavity, and was absent in the inferior and/or central part of the cavity. This morphology was similar to the so-called fibroadipose meniscoid of the lumbar zygapophysial joint that is usually seen in adults. In mid-term fetuses, there was evidence suggesting that a mesenchymal tissue plate was separated from a roof of the joint cavity. In late-stage fetuses, the thickness (less than 0.15 mm) was usually the same as, or less than that at mid-term, and the disk-like structure was often flexed, folded and fragmented. Therefore, in contrast to the zygapophysial meniscoid as a result of aging, the present disk-like structure was most likely a temporary product during the cavitation process. It seemed to be degenerated in late-stage fetuses and possibly also in newborns. Anomalies at the craniocervical junction such as Chiari malformations might accompany this disk-like structure at the median atlanto-axial joint even in childhood.
在对中期和晚期胎儿的观察中，我们在寰枢正中关节的前部发现了一个关节盘样结构。在中期，相对于关节周围骨骼的大小，该盘样结构较厚（0.1 - 0.15毫米）。然而，它并未完全分隔关节腔，且在关节腔的下部和/或中部不存在。这种形态与通常在成年人中见到的腰椎关节突关节的所谓纤维脂肪半月板样结构相似。在中期胎儿中，有证据表明间充质组织板从关节腔顶部分离。在晚期胎儿中，其厚度（小于0.15毫米）通常与中期相同或小于中期，并且盘样结构常常弯曲、折叠和破碎。因此，与因衰老形成的关节突半月板不同，目前的盘样结构很可能是空洞化过程中的一个临时产物。它似乎在晚期胎儿甚至新生儿中发生退化。即使在儿童期，颅颈交界区的异常如Chiari畸形可能与寰枢正中关节处的这个盘样结构同时出现。
