INTRODUCTION : In treating of acute unstable thoracolumbar spine fractures, current trend is a toward short segment instrumentation to spare the motion segments. Many authors reported the result of short instrumentation and fusion, but there have been few reports about the effect of additional screw fixation at fractured vertebra in posterior short segment instrumentation and fusion. Therefore, the objective of this study is to compare the results of treatment between with/without screw fixation at the fractured vertebra in posterior short segment pedicle screw fixation. MATERIAL AND METHODS : Twenty-three patients with unstable thoracolumbar spine fractures were treated with posterior short segment instrumentation and fusion. Eleven cases classified into group A were not fixed at the fractured vertebre. They were followed up to average 45 months(24-79). Twelve cases classified into group B were treated with screw fixation at the injured vertebra and followed up to average 38 months(14-78). Authors evaluated the radiologic assessment, such as wedge angle of fractured body, local kyphotic angle and wedge index(the ratio of anterior body height to posterior body height), the neurologic assessment by Frankel grade system and functional assessment by Denis system. RESULTS : There was no complication resulted from additional pedicle screw fixation at fractured level. In rediologic assessment, wedge angle were measured at preoperative, postoperative and last follow-up time as follows; in group A, 22.2degrees -11.3degrees -14.1degrees and in group B, 19.5degrees -8.8degrees -9.8degrees . The local kyphotic angle measured were 17.9degrees -7.0degrees -14degrees in group A and 17.1degrees -6.3degrees -7.9degrees in group B. The wedge index were 42.9%-22.6%-28.5% in group A and 40%-19.5%-22.4% in group B. At last follow-up time, eight eases showed Frankel grade E and three cases showed grade D in group A, and all cases of group B were Frankel E. Denis pain score were satisfctory in all of both group and Denis work score were also satisfactory in two group except one case of group A. CONCLUSIONS : Additional screw fixation at fractured verteba did not cause any complication. There was no significant difference in reduction rate between two groups(P>0.05), but group B showed better maintenance of correction of kyphotic deformity than that of group A(P<0.05). In conclusion, it seems that additional screw fixation at fractured level may be better method in maintaining asgittal alignment and decreasing the risk collapsing of body.