Latent mobility of osteoporotic vertebral compression fractures

PURPOSE: To describe the property of latent mobility in osteoporotic vertebral compression fractures (VCFs) and discuss its clinical significance. MATERIALS AND METHODS: This was a retrospective case series of 14 patients with 14 painful osteoporotic VCFs who were comfortably confined to the supine position overnight for the purpose of vertebral height restoration. There was sufficient additional vertebral height restoration the following morning to allow percutaneous vertebroplasty (PV) in some patients when this had initially been deemed unsafe or technically impossible. Anterior vertebral height of the index VCF was measured from the preoperative standing lateral, immediate cross-table supine lateral, and postconfinement cross-table supine lateral radiographs as well as the first postoperative standing lateral radiograph. Dynamic mobility was defined as the difference in anterior vertebral height between preoperative standing lateral and immediate cross-table supine lateral radiographs. Latent mobility was defined as difference in anterior vertebral height between immediate cross-table supine lateral and postconfinement cross-table supine lateral radiographs. Postoperative vertebral height restoration was defined as the difference in anterior vertebral height between preoperative and first postoperative standing lateral radiographs. Mean patient age was 81.0 years, and mean fracture age was 83.6 days. RESULTS: Dynamic mobility averaged +4.7 mm (range, -2.1 to +12.6 mm; P = .001). Latent mobility averaged +2.7 mm (range, -1.9 to +15.5; P < .02). The average sum of preoperative dynamic and latent mobility (+7.4 mm; range -1.0 to +17.0; P < .001) was not different from final postoperative vertebral height restoration (P > .4). PV was successfully accomplished in all cases. CONCLUSIONS: Latent mobility occurs in some VCFs and contributes to vertebral height restoration. Recognition of latent mobility may permit vertebroplasty in some patients in whom the procedure had otherwise been deemed unsafe. Reports of vertebral height restoration following vertebral augmentation should account for that proportion resulting from dynamic and latent mobility.