VCOM Research Day Program Book 2023

Medical Student Research Biomedical

31 Evaluation of Obturator Nerve Fascicular Topography Using Landmark Morphometrics- A Pilot Study

Hasti Izadpanah, BS, Jonathan Millard, PHD, Kelly C. S. Roballo, DVM, PhD Corresponding author: hizadpanah@vcom.edu

Edward Via College of Osteopathic Medicine-Virginia Campus

While the overall macro-anatomy of peripheral nerve trunks in the lower extremities are well researched there is still a little known about microanatomy such as nerve diameter, fascicles number, length, route, as they travel along each of their path. However, this information is important in case of peripheral nerve injury, where nerve grafting would be used. Peripheral nerve injuries (PNI) occur in approximately 1.64% of people who have had trauma involving the upper or lower limb. However, only about 50% of those who are treated for PNI fully recover after treatment. Given the complexity of fascicular movement through the peripheral nerves, characterization of intra-neural fascicular variability has proven challenging. The aim of this pilot study was to analyze the variability of the fascicular arrangement of the obturator nerve using landmark morphometrics and have a better understanding of the morphology, anatomy, and functionality of this nerve as it travels up and down the lower lim. Elucidating subtle variation in fascicular topography could prove useful in clinical applications. Obturator nerves from the 25 formalin-fixed whole body donors were isolated. Donor sex was noted, and measurements were taken as a proxy for body size (ASIS-medial malleolus and tibial tuberosity to medial malleolus) Obturator nerves were cross

sectioned into nine equality divided segments and used for imagining and future analysis. Donors were categorized by fascicle number and laterality. For this pilot study, 9 cross sections from 9 donors had 10 fascicles which was used for our analysis. 130 landmarks were collected via semi-landmark techniques using tpsdig232 (v. 2w32). Generalized Procrustes analysis using MorphoJ (v.1.07a) was performed to determine the mean landmark configuration, and a principal component analysis was used to explore variability in fascicular topography. Wireframe graphs, lollipop diagrams, and transformation grids were generated to evaluate and visualize findings. Overall nerve diameter of obturator nerve on 25 donors on the right was 2.29cm and 2.28cm on the left. Nerve length on the right was 10.86cm and 10.83cm was on the left. Principal component analysis revealed eight principal components, with the first two principal components explaining 64.6% of the overall shape variation. Both PC1 and PC2 show peripheral fascicles remaining more consistently located, while the direction and magnitude of variability demonstrated by the lollipop diagrams suggest much more variation in the relative locations of more interior fascicles.

Obtaining a concise boundary for some of the fascicles proved to be more challenging than originally anticipated. We also acknowledge using landmarking to extract more information regarding microanatomy is a novel approach to the topic. However, the result of this study showed that there are some common patterns found among fascicles of the lower limb. of note, the location of the fascicles was variable causing predicted differences in the non fascicle tissue measurement between nerve trucks. The variability would affect the future nerve grafting goals and further research needs to be done on this area as well. We are hoping by finding common patterns we can get closer to finding out about fascicles path and improve our clinical approach to nerve grafting, surgical repair, and electrode implant.

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