To evaluate the relationship between the level of screw fixation and the stability of the segment of endplate fracture after posterior pedicle screw instrumentation for thoracic and lumbar burst fractures.

The 41 patients of burst fractures who had been operated with pedicle screw instrumentation were retrospectively evaluated. The patients were divided into two groups by the levels of screw fixation. One group was treated with screws fixed by one-level to the direction of fractured endplate (One-level group, 16 cases). The other group was treated with screws fixed by two-level to the direction of endplate fracture (Two-level group, 25 cases). The two groups were compared by the radiographic changes of kyphotic angle between the day of surgery and 6 months after surgery.

At the 6 months, one-level group showed the change of kyphotic angle of 17.5±2.4 degrees, which was different from two-level group of 5.2±0.8 degrees (p=0.000).

In posterior pedicle screws fixation for thoracic and lumbar burst fractures, 2 vertebrae to the direction of the endplate fracture should be included to prevent the postoperative kyphotic change.