The VAS score of low back pain showed no significant difference between groups at all time points after operation ( P > 0.05 ) ; the VAS score of leg pain in the DM group was significantly lower than that in the control group at all time points ( P < 0.05 ) , and than those in the mannitol group at 3 , 24 , 48 , and 96 hours after operation ( P < 0.05 ) .