STUDY DESIGN: Retrospective. OBJECTIVES: To investigate outcomes between short and long segment posterior instrumentation of thoracolumbar burst fractures with a load sharing score of 7 or more. SUMMARY OF LITERATURE REVIEW: Short segment instrumentation has been recommended in thoracolumbar burst fractures with a load sharing score of 6 or less, and long segment instrumentation has been recommended for those with a score of 7 or more. However, this standard is controversial. MATERIALS AND METHODS: From March 2006 to January 2014, 45 patients with thoracolumbar fractures with a load sharing score of 7 or more were treated with posterior instrumentation. They were divided into two groups: short (group S) and long segment (group L) groups. Radiologic results were evaluated on the basis of the kyphotic angle and anterior column height. Complications were also reviewed. RESULTS: Groups S and L consisted of 13 and 32 patients and had mean ages of 48.3 and 47.3 years, respectively. In group S, the anterior column height increased from 56.62% to 76.23% postoperatively, and remained at 71.15% at follow-up. The kyphotic angle decreased from 16.27degrees to 7.55degrees postoperatively, and was 13.17degrees at follow-up. In group L, the anterior column height recovered from 49.67% to 70.52% postoperatively, and was 63.73% at follow-up. The kyphotic angle decreased from 20.08degrees to 6.80degrees postoperatively, and was 14.18degrees at follow-up. The changes in the anterior column height and kyphotic angle were not significantly different between groups S and L. Seven cases had complications and the number of cases with complications was not significantly different between groups S and L. CONCLUSIONS: Short and long segment instrumentation of thoracolumbar fractures with a load sharing score of 7 or more did not achieve significantly different results.