Branching patterns of the common and superficial fibular nerves in fetus.

In this study, we focused on finding out whether branching patterns of the common fibular (CFN) and superficial fibular (SFN) nerves change throughout the early period of life. The popliteal fossa and legs on both sides of 20 fetuses (13 females and 7 males) were dissected. The ages of the fetuses varied between 20 and 36 weeks. The levels where the CFN diverged from the sciatic nerve, the CFN diverged to its terminal branches, and the cutaneous branches of the SFN became superficial and diverged were evaluated, together with the similarity of the patterns of these nerves on both sides. We observed that, comparing with the results of previous studies on adults, both the sciatic and the CFNs in the fetuses were diverging into their terminal branches more distally. Additionally, the SFN appeared to become superficial more proximally in the fetus than in the adult. SFN was piercing the crural fascia before diverging into its terminal branches in 29 legs. Only in 8 of them, it was becoming superficial within the middle one-third of the leg, which was observed more frequently in males (42.9% of 14 legs) than in females (13.3% of 15 legs). But there was no statistically significant gender difference (P = 0.07). The medial dorsal cutaneous (MDCN) and intermediate dorsal cutaneous (IDCN) nerves which were piercing the crural fascia separately were observed in 27.5% of the subjects, all females. In these, MDCN was piercing the fascia superior to the level where the SPN becomes superficial, whereas the IDCN was piercing it to a level lower to this and always in the inferior one-third of the leg. We suggest that the detailed information about the branching patterns of the CPN and SPN in early ages will be beneficial, particularly in tumor and deformity surgery. The reason for different patterns and piercing levels of the nerves may be the effect of the elongating extremity during aging that enforces the fascia and modifies its position with a more stable structure, the nerve.