PREDICTING FAILURE OF THORACIC VERTEBRAE WITH SIMULATED AND ACTUAL METASTATIC DEFECTS

Indications for operative treatment in spinal metastatic disease depen d on estimates of vertebral loadbearing capacity, There are no noninva sive diagnostic tools for estimating vertebral loadbearing capacity in the presence of a metastatic lesion, Thus, relationships between vert ebral failure load and measurements from computed tomography data were investigated to determine if measurements that account for defect siz e and hone density can predict loadbearing capacity better than can de fect size alone, Cylindrical defects were created in thoracic vertebra e of 20 anatomic specimen spinal segments, with 10 other segments serv ing as controls, Five vertebrae with actual metastatic defects also we re tested, Vertebrae were scanned using quantitative computed tomograp hy, and the defect size and the axial rigidity of the midvertebral cro ss section were calculated using an image analysis program, The spinal segments were tested to failure using a combination of axial compress ion and anterior flexion, Linear regressions between axial rigidity an d absolute failure load showed a high positive correlation, but there was no correlation between defect size and failure load, Axial rigidit y may prove useful as a noninvasive assessment of vertebral loadbearin g capacity in patients with spinal metastatic disease.