Analysis of Injected Cement Volume and Clinical Outcomes Following Balloon-Assisted Kyphoplasty in a Series of 368 Patients.

Objective: Balloon-assisted kyphoplasty (BAK) is a modified vertebroplasty technique developed to treat vertebral compression fractures (VCFs) secondary to osteoporosis. This study investigates the association between injected cement volume and the development of subsequent VCFs after BAK. Methods: A retrospective analysis of 368 patients who underwent BAK at a single institution was performed from 2001 to 2021. Inclusion was defined by at least 2 years of follow-up. Clinical characteristics and outcomes following BAK, including subsequent fractures at adjacent and remote levels, were identified. Patients that underwent a thoracic BAK were stratified by injected cement volume: below or equal to the median (<= 6.0 mL, 265 vertebrae) or above the median (> 6.0 mL, 144 vertebrae). Patients that underwent a lumbar BAK were similarly stratified: below or equal to the median (<= 8.0 mL, 233 vertebrae) or above the median (>8.0 mL, 160 vertebrae). Results: A total of 802 vertebrae were treated. The average volume of cement was recorded in the thoracic (6.2 +/- 1.9 mL) and lumbar (7.8 +/- 1.8 mL) vertebrae. In the thoracic spine, vertebrae that were injected with > 6.0 mL of cement underwent a greater change in local kyphotic angle (P = 0.0001) and were more likely to develop adjacent-level VCFs (P = 0.032) after kyphoplasty. Univariate analysis did not elucidate any additional risk factors. There were no statistical differences in clinical outcomes between the three groups of lumbar vertebrae. Conclusions: Larger volumes of injected cement were associated with a greater change in local kyphosis and subsequent adjacent-level fractures after BAK in the thoracic spine. This association was not found in the lumbar spine. Close attention to injected cement volumes must be made in the thoracic spine and patients who undergo significant kyphotic correction should be carefully observed postoperatively.