Subsequent Vertebral Fractures Post Cement Augmentation of the Thoracolumbar Spine: Does it Correlate With Level-specific Bone Mineral Density Scores?

STUDY DESIGN A case-control study. OBJECTIVE In this study, we investigated the correlation between level-specific preoperative bone mineral density and subsequent vertebral fractures. We also identified factors associated with subsequent vertebral fractures. SUMMARY OF BACKGROUND DATA Complications of cement augmentation of the spine include subsequent vertebral fractures, leading to unnecessary morbidity and more treatment. Ability to predict at-risk vertebra will help guide management. METHODS We studied all patients with osteoporotic compression fractures who underwent cement augmentation in a single institution from November 2001 to December 2010 by a single surgeon. Association between level-specific bone mineral density T-scores and subsequent fractures was assessed. Multivariable analysis was performed to identify significant factors associated with subsequent vertebral fractures. RESULTS 93 patients followed up for a mean duration of 25.1 months (12-96) had a mean age of 76.8 years (47-99). Vertebroplasty was performed in 58 patients (62.4%) on 68 levels and kyphoplasty in 35 patients (37.6%) on 44 levels. Refracture was seen in 16 patients (17.2%). The time to subsequent fracture post cement augmentation was 20.5 months (2-90). For refracture cases, 43.8% (7/16) fractured in the adjacent vertebrae. Subsequently fractured vertebra had a mean T-score of -2.860 (95% confidence interval -3.268 to -2.452) and nonfractured vertebra had a mean T-score of -2.180 (95% confidence interval -2.373 to -1.986). A T-score of -2.2 or lower is predictive of refracture at that vertebra (P = 0.047). Odds ratio increases with decreasing T-scores from -2.2 or lower to -2.6 or lower. A T-score of -2.6 or lower gives no additional predictive advantage. After multivariable analysis, age (P = 0.049) and loss of preoperative anterior vertebral height (P = 0.017) are associated with refracture. CONCLUSION Level-specific T-scores are predictive of subsequent fractures and the odds ratio increases with lower T-scores from -2.2 or less to -2.6 or less. They have a low positive predictive value, but a high negative predictive value for subsequent fractures. Other significant associations with subsequent refractures include age and anterior vertebral height. LEVEL OF EVIDENCE 4.