Abstract
Background: Brachial plexus injury (BPI) occurs when the brachial plexus is compressed, stretched, or avulsed. Although rodents are commonly used to study BPI, these models poorly mimic human BPI due to the discrepancy in size. The objective of this study was to compare the brachial plexus between human and Wisconsin Miniature SwineTM (WMSTM), which are approximately the weight of an average human (68–91 kg), to determine if swine would be a suitable model for studying BPI mechanisms and treatments. Methods: To analyze the gross anatomy, WMS brachial plexi were dissected both anteriorly and posteriorly. For histological analysis, sections from various nerves of human and WMS brachial plexi were fixed in 2.5% glutaraldehyde and then myelinated axons were labeled using 2% osmium tetroxide before being counter-stained with Masson’s Trichrome. Results: Gross anatomy revealed that the separation into 3 trunks and 3 cords is significantly less developed in the swine than in human. In swine, it takes the form of upper, middle, and lower systems with ventral and dorsal components. Histological results showed that despite the similarity in body size between the miniature swine model and humans, there was some discrepancy in nerve size and the number of the myelinated axons. The WMS had significantly fewer myelinated axons than humans in median (p = 0.0009), ulnar (p = 0.0001), and musculocutaneous nerves (p = 0.0451). The higher number of myelinated axons in these nerves for humans is expected, because there is a high demand of fine motor function in the human hand, with more motor units. Due to the stronger shoulder girdle muscles in WMS, the WMS suprascapular nerves were larger than in human. Conclusion: Overall, the WMS brachial plexus is similar in size and origin to human making them an excellent model to study BPI. Future studies analyzing the effects of BPI in WMS should be conducted.
