Bone mineral density in patients with symptomatic vertebral compression fractures after instrumented spinal fusion: A retrospective analysis

Background: Few studies have been published concerning about the osteoporotic symptomatic vertebral compression fractures (VCFs) following instrumented spinal fusion for degenerative spinal disease. Purpose: The purpose of this study was to evaluate the incidence of symptomatic VCFs and the differences in the timing of occurrence and bone mineral density (BMD) between patients with adjacent and remote VCFs after instrumented spinal fusion. Methods: We performed a retrospective analysis of 1,936 patients who received posterior instrumentation for degenerative spinal disease at our institution and were followed-up for at least 3 years. Dual-energy X-ray absorptiometry surveys were arranged, and symptomatic subsequent VCFs were identified during regular follow-up. Eligible patients were divided into two groups (adjacent or remote to instrumented spinal fusion, based on the location of their VCFs. The Wilcoxon signed-rank test or chi-square test was used to assess between-group differences. Linear regression analysis was used to examine the relationship between the timing of the occurrence of VCFs and BMD (T-score). Results: The incidence of symptomatic VCFs following instrumented lumbar spine fusion was 2.37% (46/1,936), which accounted for 20.53% (46/224) of patients with VCFs. Linear regression analysis revealed a positive trend between the timing of the occurrence of symptomatic VCFs and values of BMD (T-score). The mean time to develop adjacent VCFs was 6.8 months, while that to develop remote VCFs was 13.7 months (p ＜ 0.05). Conclusion: Symptomatic adjacent VCFs occurred much earlier than remote VCFs. Device-related osteoporosis may be one of risks in subsequent VCFs, which highlight the importance of osteoporosis medication.