Major medical outcomes with spinal augmentation vs conservative therapy

Abstract

Importance: The symptomatic benefits of spinal augmentation (vertebroplasty or kyphoplasty) for the treatment of osteoporotic vertebral compression fractures are controversial. Recent population-based studies using medical billing claims have reported significant reductions in mortality with spinal augmentation compared with conservative therapy, but in nonrandomized settings such as these, there is the potential for selection bias to influence results.

Objective: To compare major medical outcomes following treatment of osteoporotic vertebral fractures with spinal augmentation or conservative therapy. Additionally, we evaluate the role of selection bias using preprocedure outcomes and propensity score analysis.

Design, setting, and participants: Retrospective cohort analysis of Medicare claims for the 2002-2006 period. We compared 30-day and 1-year outcomes in patients with newly diagnosed vertebral fractures treated with spinal augmentation (n = 10,541) or conservative therapy (control group, n = 115,851). Outcomes were compared using traditional multivariate analyses adjusted for patient demographics and comorbid conditions. We also used propensity score matching to select 9017 pairs from the initial groups to compare the same outcomes.

Exposures: Spinal augmentation (vertebroplasty or kyphoplasty) or conservative therapy.

Main outcomes and measures: Mortality, major complications, and health care utilization.

Results: Using traditional covariate adjustments, mortality was significantly lower in the augmented group than among controls (5.2% vs 6.7% at 1 year; hazard ratio, 0.83; 95% CI, 0.75-0.92). However, patients in the augmented group who had not yet undergone augmentation (preprocedure subgroup) had lower rates of medical complications 30 days post fracture than did controls (6.5% vs 9.5%; odds ratio, 0.66; 95% CI, 0.57-0.78), suggesting that the augmented group was less medically ill. After propensity score matching to better account for selection bias, 1-year mortality was not significantly different between the groups. Furthermore, 1-year major medical complications were also similar between the groups, and the augmented group had higher rates of health care utilization, including hospital and intensive care unit admissions and discharges to skilled nursing facilities.

Conclusions and relevance: After accounting for selection bias, spinal augmentation did not improve mortality or major medical outcomes and was associated with greater health care utilization than conservative therapy. Our results also highlight how analyses of claims-based data that do not adequately account for unrecognized confounding can arrive at misleading conclusions.

Figure 1

Major medical outcomes following vertebral compression fracture in the traditional multivariate analysis. A, Survival. B, Time without a major medical complication. Hazard ratios (HR) were calculated with Cox proportional hazards model adjusted for year of fracture diagnosis, patient demographics and comorbidities, fracture level, and use of advanced imaging.

Figure 2

Major medical complications as a function of time from spinal augmentation. A, Overall major medical complications (event) relative to the time of spinal augmentation (day 0). B, Major medical complications (event) within one month of the procedure. Pre-procedure events are indicated as negative time.

Figure 3

Major medical outcomes following vertebral compression fracture in the propensity score matched analysis. A, Survival. B, Time without a major medical complication. Hazard ratios (HR) were calculated with matched-sample Cox proportional hazards model.