To analyze the results of posterior reduction with AO internal fixator or screw-rod system in thoracolumbar fracture and to find an adequate method of treatment.

We analyzed 40 cases of unstable thoracolumbar fractures who were operated with posterior approach without additional anterior approach. All cases were divided into two groups by the instrument used: Group A (25 cases) with AO internal fixator and Group B (15 cases) with screw-rod system. They were classified according to AO classification.

There was no significant difference in correction and maintenance of sagittal index among types of AO classification except neurological recovery which was better in Type A. AO internal fixator had better results than screw-rod system in correction and maintenance of sagittal index, but no difference in neurological recovery. Eleven cases had more than 5 degrees of correction loss at final follow-up. In these cases, we found several findings; decreased vertebral body height, decreased disc height, bony collapse around screw at superior segment, metal loosening between rod and screw and metal breakage of screw.

We concluded that AO internal fixator was good for the posterior reduction of thoracolumbar fracture in this study. But we think that continuous follow-up and further study are needed.