Effect of Traction on the Head During Vaginal Delivery on Brachial Plexus Strain.

OBJECTIVE: Previous simulations have shown the effect of traction during delivery on brachial plexus (BP) strain modeled as a single element. We sought to determine the effect of head angle and traction force on BP strain, specifically at Erb′s point and the posterior cord (PC) in a multi-“filament” 3D model of the BP. STUDY DESIGN: Using an instrumented biofidelic neonatal BP model, position-sensing system, and data acquisition system, we applied 0, 5, and 10 lbs of axial traction at 0°, 15°, 30°, 45°, and 60° in the downward direction, such that total traction force increases with angle (up to 20 lbs total for 10 lbs axial traction). For each simulation, we measured maximum anterior BP strain at Erb′s point and the PC. N=15. Data were analyzed with ANOVA, with p<0.05 considered significant. RESULTS: As shown in the table, increasing traction force magnitude significantly increases strain at Erb’s point (table) and PC (not shown), regardless of angle of delivery. The effect of magnitude and direction of force is significant at all traction force levels.Table: Erb’s Point Strain (%)CONCLUSION: BP strain can be minimized at Erb’s point and the PC by aligning the fetal head with the trunk and reducing traction during delivery.