Background: In percutaneous vertebroplasty, bone cement leakage is the overriding complication.There are many reasons influence bone cement leakage.Such as bone cement viscosity, bone cement injection speed and the size of vertebral crevice.To evaluate the bone cement leakage with gelatin sponge pre-injection during percutaneous vertebroplasty (PVP) operation, with exsomatize vertebral bodyies as experimental subjects.