A review of 106 consecutive patients who had operative stabilization of thoracolumbar fractures revealed that 16 patients had surgery 4 months to 13 years after injury, for chronic instability. In these 16 patients, there were 8 wedge-compression fractures, 6 flexion-distraction injuries, 1 burst fracture, and 1 fracture-dislocation. All six patients with flexion-distraction injuries and the two patients with either a burst fracture or a fracture-dislocation had good results. Only two of the eight patients with wedge-compression fractures had good results. We concluded from this study that: (a) instability that presents without a progressive spinal deformity may go unrecognized; (b) all types of spine fractures can produce chronic, painful instability; and (c) poor results predominate in wedge-compression fractures operated more than 13 months after injury, regardless of the type of surgical treatment rendered.