Objective To establish a reliable unstable pelvic fracture model with sacral plexus stretch injury in goats and to detect electrophysiological signals when pelvis is shifted in different orientations and distance.Methods Twenty-four goats were divided into three groups of 8 animals each:pelvic longitudinal displacement was induced in group A,pelvic lateral displacement in group B,and pelvic dorsal displacement in group C.Animal left L6 and S1 nerve root and initial segment of sciatic nerve were exposed to connect stimulating and receiving electrodes respectively.Left pelvis was shifted at the speed of 0.25 mm/s to produce the model of unstable pelvic fracture with sacral plexus stretch injury.Electrophysiological signals of L6 and S1 were recorded when the placement of pelvis was 0,0.5 and 1.0 cm respectively.Results With pelvic displacement,the threshold potential,maximum stimulus potential and incubation period were gradually increased,but the peak-to-peak value became smaller gradually.When the pelvis displaced 0.5 cm at different orientations,group A showed improved threshold potential and incubation period (P ＜0.05),decreased peak-to-peak value (P ＜0.05),and no significant change in maximum stimulus potential(P ＞0.05);group B only showed lowered peak-to-peak value with no significant variations in other electrophysiological signals (P ＜ 0.05);group C had no significant variations in all electrophysiological signals (P ＞ 0.05).When the pelvis displaced 1.0 cm at different orientations,groups A and B showed improved threshold potential,maximum stimulus potential and incubation period (P ＜ 0.05) and lowered peak to peak value (P ＜ 0.05);group C showed higher incubation period with no significant variations in other electrophysiological signals(P ＜0.05).Between groups,the amplitude of variation in electrophysiological signals was the most in group A and the least in group C.Conclusion After unstable pelvis fracture in goats,sacral plexus stretch injury is the most serious in longitudinal displacement of the pelvis.