The entrapment mechanism of the orbital blowout fracture is due to the phase difference of the movement of solid, bony, and elastic, soft orbital structures. The mechanism is enforced secondarily by the increased hydraulic pressure of the orbital contents that results from the orbital and periorbital edema that occurs shortly after the trauma. In addition, according to our concept, the primary causative factor in the mechanism of the orbital blowout fracture is the buckling force, confirmed by our clinical analysis of 101 cases of pure blowout fractures.