Spinal canal remodelling after stabilization of thoracolumbar burst fractures

Spinal canal areas were measured prospectively in 22 consecutive burst fractures of the thoracolumbar junction, preoperatively, within 1 week postoperatively and 1 year after operation. Preoperative canal encroachment averaged 38% (range 10%-70%) of the estimated original area. The 11 patients with neurological impairment had a significantly more severe initial canal encroachment (mean 48%) than those who were neurologically intact (mean 33%). Postoperatively, canal encroachment had decreased to a mean of 18% (range 0%-62%). Within 12 to 15 months postoperatively, canal encroachment was further reduced by resorption of bone fragments to a mean of 2%. The largest observed remaining encroachment was 29%. The amount of bone resorption correlated significantly with the persistent postoperative encroachment. A critical appraisal of the methods used to assess the pre-fracture canal area revealed that reconstructing the vertebral foramen of the fractured vertebra on CT scans substantially overrated the original area as compared with averaging the canal area of the two adjacent vertebrae.