Range of spinal shortening and percentage of spinal shortening of single spinal motion segment (total height of posterior edge of vertebral body + cephalad disc + caudal disc) were calculated using the following equation on the postoperative lateral radiograph. Range of Spinal shortening: X = (A + B)/2 + C + D − E, percentage of spinal shortening of single spinal motion segments: Y = X/[(A + B)/2 + C + D] × 100%, where A is the height of posterior edge of cephalad vertebral body, B is the height of posterior edge of caudal vertebral body C is the height of posterior edge of the cephalad disc, D is the height of posterior edge of caudal disc, and E is the height of posterior edge of titanium mesh.