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.
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.
Spinal augmentation (vertebroplasty or kyphoplasty) or conservative therapy.
Main Outcomes and Measures
Mortality, major complications, and health care utilization.
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
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.