Forced Needle Advancement During Needle-Nerve Contact in a Porcine Model

BACKGROUND: In this study, we determined whether needle advancement during needle-nerve contact (forced needle-nerve contact) is associated with a higher risk of nerve injury compared with needle-nerve contact without needle advancement (nonforced needle-nerve contact). METHODS: In 8 anesthetized pigs, the brachial plexus nerves underwent forced (0.15 Newton) or nonforced (0.0 Newton) needle-nerve contact without nerve penetration. The grade of nerve injury was histologically assessed using an objective score ranging from 0 (no injury) to 4 (severe injury). RESULTS: Sixty-nine nerves, including controls, were examined. Histology revealed a significant difference between forced and nonforced needle-nerve contact (median [interquartile range] 3 [2-4] vs 2 [1-2]; P = 0.004). Myelin damage and intraneural hematoma occurred only after forced needle-nerve contact. CONCLUSIONS: The severity of structural nerve injury after needle-nerve contact was directly related to force exposure via needle advancement.