Postoperative bedrest improves the alignment of thoracolumbar burst fractures treated with the AO spinal fixator.

BACKGROUND A loss of reduction due to inadequate support of the anterior column when using short-segment instrumentation to treat burst fracture and novel methods for support of the anterior column through a posterior approach to augment posterior instrumentation have been reported in the literature. We hypothesized that if anterior column support is an important adjunct to posterior short-segment instrumentation, then avoidance of axial load until sufficient anterior column healing occurs, allowing load-sharing with the implant, would improve spinal alignment at follow-up. METHODS We conducted a retrospective cohort study in which consecutive patients who had instrumentation and fusion with the AO spinal fixator were immediately ambulated after surgery or had 4 weeks of bedrest. We measured kyphosis and wedge angles preoperatively, immediately postoperatively and at the time of final follow-up. We used radiologic measures to assess instrumentation and bone failure. RESULTS We found significant differences in the mean loss of wedge and kyphosis angle correction between patients immediately ambulated and those who had 4 weeks of bedrest (0.71 masculine v. - 4.73 masculine for wedge and 1.81 masculine v. - 6.55 masculine for kyphosis, respectively). There was significant correlation between instrumentation and bone failure in both the immediate ambulation and bedrest groups. CONCLUSION Bedrest improves the maintenance of intraoperative sagittal alignment correction, which is in agreement with the theory that inadequate support of the anterior spinal column is the mechanism for loss of reduction when using short-segment instrumentation to treat burst fractures. Therefore, addressing the anterior column directly through anterior surgery or by employing novel techniques in posterior surgery is recommended if one of the goals of treatment is to maintain the sagittal correction achieved at the time of surgery. Trying to achieve this goal by addressing posterior implant design or bone quality alone will not be successful because instrumentation and bone failure occur together.