Study design: retrospective clinical study .

Objective: To study radiological late results after posterior stabilization of thoracolumbar fractures with internal fixation. To know factors related with loss of correction and hardware failure.

Summary of background data: The posterior approach using an internal fixator is a standard procedure for stabilizing the injured thoracolumbar spine. None of the surgical techniques used was able to maintain the corrected the kyphosis angle.

Methods: Forty-five patients with thoracolumbar fractures were included in the study. The inclusion criterion was the presence of fracture through the T11-L3 vertebrae without neurologic compromise. The Load-sharing classification has been used for all patients to determine the fracture severity. Surgical techniques (short or long instrumentation) , preoperative and postoperative radiographs ( Cobb technique) and follow-up records of all patients were reviewed carefully from the time of surgery until final follow-up assessment.

Results: 13 patients were treated using short-segment instrumentation (two disc spaces) and 32 patients with long-segment instrumentation (more than two disc spaces). The mean follow-up was 3.4 years (range 1 to 11 years). The mean preoperative Cobb angle was 16.1 degrees and after surgery the mean angle was 6.8° representing an average correction of 9.2 ° . At follow-up assessments the mean Cobb angle was 13.2° representing a loss of correction of 6.4°. Implant failure ( 5 loosening and 8 breakage) was seen in 28.8% of patients: 6/14 (42%) of patients receiving short instrumentation and 7/31 (22%) of patients with long instrumentation. Hardware failure was seen in 53.3% of patients with Cobb angle preoperative more than 20° and in 16.6% of patients with Cobb angle less than 20°.

Conclusions: Radiological behaviour of thoracolumbar fractures treated with posterior instrumentation without anterior support was worse than expected. Hardware failure was related with Cobb angle fracture > 20°, postoperative correction superior than 10° and short pedicular instrumentation technique.