Unstable thoracolumbar fracture (vertebromedullary traumatic lesion) is often the cause of poor sequelae, in lumbar pain caused by changes in the physiological sagittal profile, and sequelae of a neurologic nature. Thus, the concept of instability is further defined. The authors present 33 cases of burst type thoracolumbar fractures treated by transpedicle instrumentation using the following systems: MVF, Omega 21. Follow-up was obtained after rom 1 to 9 years. Results were: clinicalradiographic criteria (1. fusion, 2. deformity, 3. pain, 4. neurologic function). There was remodeling of the spinal cord canal in cases operated on. The authors conclude that a correct evaluation of instability of burst fractures and the consequent treatment of choice (transpedicle fixation) allows for a high favourable index of the functional capacity in these patients.