Early embryonic development of long tendons in the human foot

Abstract

To examine a common plantar tendinous plate for long flexors of the toe and fingers in human embryos, we observed sections of 10 embryos at 5-6 weeks (crown-rump length or CRL 15-21 mm). The heel or tuber of the calcaneus was underdeveloped in 3 embryos with CRL 15 mm and the talus appeared not to be piled up on the calcaneus but these two bones were arranged along the lateromedial axis. As reported in the hand, we demonstrated, in the deep side of tarsal bones, a common tendinous plate formed by a joining of the flexor halluces longus and flexor digitorum longus tendons. In the tendinous plate, much or less, some connections between tendons seemed to remain even after birth to provide much greater types of tendon anomalies than in the hand. In addition, we postulated a hypothetical change in course of the peroneus longus tendon. In the initial phase, because of the underdeveloped calcaneus, the peroneus tendon might take an almost straight course similar to long flexor tendons. However, at 6 weeks and later, the inferomedially expanding calcaneus beneath the talus was likely to push the tendon to the cuboid bone.

Ontogenic transformation of the ankle from the initial mediolateral arrangement of the calcaneus and talus: A histological study of human embryos and early fetuses

“…It is not well-known that the cartilaginous talus of an embryo is unlikely to "ride over" the calcaneus. Our group (Uchiyama et al, 2014;Yamamoto et al, 2016) as well as classical studies (e.g., Bardeen, 1905; Figure 1) reported that the initial calcaneus was parallel with the talus on the foot planta of human embryos. Therefore, the initial tarsal bones have a hand-like arrangement (Figure 1b).…”

“…There were sagittal sections from four fetuses and transverse sections from two fetuses. Some of these specimens were analyzed in our previous studies (Uchiyama et al, 2014;Yamamoto et al, 2016).…”

Study on Tendinous Connections Between Flexor Hallucis Longus and Flexor Digitorum Longus

“…The FHL and FDL are major tendons of the foot which originate from the common tendinous plate that may result in existence of various types of connections between them [1,9]. Moreover, their routine use in reconstructive surgeries of foot and ankle calls for compre hensive knowledge of their connections.…”