Insufficient Augmentation of Bone Cement Causes Recompression of Augmented Vertebra after Balloon Kyphoplasty

INTRODUCTION: Balloon kyphoplasty (BKP) is one of the most frequently used clinical methods to relieve pain caused by osteoporotic vertebral compression fracture (OVCF); it can effectively improve the body height of the vertebra. However, recompression of the augmented vertebra (RAV) is often observed after BKP. This study aimed to report factors that are associated with RAV in terms of cement augmentation. METHODS: A total of 78 patients (women, 60; men, 18) were included in this study. RAV was defined as anterior vertebral height loss (VHL), between immediate postoperation and 3 or 6 months after BKP, of more than 5.0 mm. Cement augmentation ratio (CAR) was calculated as the ratio of the maximal height of polymethylmethacrylate (PMMA) to the maximal distance between both end plates. Age, gender, fracture age, CAR, presence of medication for osteoporosis, intervertebral cleft (IVC), and cement leakage were evaluated using Fisher's exact test or Mann-Whitney U test to compare between RAV and non-RAV groups. Aforementioned variables were also analyzed using multiple logistic regression test. A P<0.05 was considered statistically significant. RESULTS: The incidence rates for RAV at 3 and 6 months were 35.9% (28/78) and 38.5% (30/78), respectively. Age (80.1 vs 74.7) was significantly higher in the RAV group, whereas CAR (69.4% vs 77.6%) was lower in the non-RAV group. A multivariate regression analysis revealed that age (odds ratio (OR)=1.12, P=0.001) and CAR (OR=0.91, P=0.001) were independently associated with RAV. CONCLUSIONS: RAV was observed in 38.5% of patients in this study. Older age and low CAR were independently associated with RAV. To prevent RAV, especially in the elderly, augmented PMMA should come in contact with both end plates.