Distinct fascicular and epineurial architecture of the obturator nerve: a comparative analysis with clinical and surgical relevance.

Peripheral nerves of the lumbar plexus share a common origin but exhibit distinct anatomical and clinical features. Although the gross anatomy of these nerves has been described, differences in cross-sectional structure remain unclear. This study compared the histological architecture of the obturator nerve (ON) with that of the femoral nerve (FN) and lateral femoral cutaneous nerve (LFCN). Eighteen nerves (ON, FN, and LFCN) from six cadavers were examined using Masson's trichrome-stained cross-sections. Morphometric analysis included the short-to-long axis ratio and fascicular area ratio. Epineurium conspicuity was assessed using a semi-quantitative 3-point scale by three blinded observers. Inter-observer agreement was evaluated using weighted kappa statistics. Non-parametric tests were used for comparisons. The ON had a significantly higher short-to-long axis ratio (0.590±0.10) than the FN (0.393±0.08) and LFCN (0.359±0.09) (P=0.031). The fascicular area ratio was also greater in the ON (0.470±0.09) than in the FN (0.262±0.09) and LFCN (0.226±0.07) (P=0.031). Epineurium scores were higher in the ON (median 2, IQR 2-2) than in the FN and LFCN (median 1, IQR 0-1) (P<0.05), with substantial inter-observer agreement (κ=0.71). The ON exhibits a distinct fascicular tissue-rich architecture with a consistently well-developed epineurium, which may contribute to its characteristic macroscopic appearance and aid anatomical identification.