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MAGNETIC RESONANCE IMAGING FINDINGS OF SUBSEQUENT FRACTURES AFTER VERTEBROPLASTY

OBJECTIVEThe biomechanical effect of injected cement has been considered as the cause of adjacent vertebral fracture (AVF) after vertebroplasty, but the clinical evidence supporting this hypothesis is still insufficient. METHODSWe retrospectively reviewed 33 patients with subsequent fractures among 278 patients who underwent percutaneous vertebroplasty at our hospital from January 2002 to December 2005. The bone marrow edema pattern of subsequent fractures on magnetic resonance imaging was analyzed in 33 patients. In addition, the relationship between the location and distribution pattern of inserted cement and site of subsequent fractures was investigated. RESULTSAmong 33 subsequent fractures, we found 13 cranial AVFs, 7 caudal AVFs, and 13 remote fractures. The incidence rate of AVFs was 7.3% of 273 patients. Among 33 subsequent vertebral fractures, 13 were cranial AVFs (Group 1), 3 were superior, 7 were inferior, and 3 were overall (23.1%, 53.8%, and 23.1%, respectively). Of 7 caudal AVFs (Group 2), 7 were superior (100%). In 13 remote fractures (Group 3), 10 were superior, 1 was inferior, 2 were overall (76.9%, 7.7%, and 15.4%, respectively). In AVFs, bone marrow edema appeared mainly toward injected cement (P = 0.005). When injected cement made a solid mass rather than interdigitation, the occurrence rate of cranial AVFs was high (P = 0.004). CONCLUSIONBone marrow edema of AVFs appeared significantly toward the previous injected cement. This phenomenon supports the idea that the biomechanical effect of injected cement is one of the causative factors which affect the occurrence of AVF after percutaneous vertebroplasty. In particular, when injected cement forms a solid mass rather than interdigitation, the risk of cranial AVF may increase.