The Association of Bone Mineral Density with Distal Junctional Kyphosis and Distal Junctional Failure After Multilevel Spine Fusions: A Systematic Review and Meta-Analysis

Background: Distal junctional kyphosis (DJK) and distal junctional failure (DJF) are known complications of adult multilevel spinal fusion surgery. Previous literature has extensively investigated proximal junctional kyphosis and proximal junctional failure, but DJK and DJF are relatively understudied. This study investigates the association between bone mineral density (BMD) and DJK/DJF via a systematic review and meta-analysis. Methods: A literature search was conducted across PubMed, Cochrane, Web of Science, Embase, and Scopus to find studies reporting DJK, DJF, and BMD. A 12-month minimum follow-up and radiographic biomarker for BMD (Hounsfield units [HU] or a T-score) individually reported for each patient type were required for inclusion. Studies that did not report individualized biomarkers but provided averaged estimates of the effect of BMD on DJK/DJF development were used for systematic review. Results: Our search yielded 12 unique studies with 1094 patients, of which 5 studies with a total of 519 patients were suitable for comparison by meta-analysis. Patients who developed DJK/DJF had significantly lower HUs (113.17 ± 33.86) than patients who did not develop DJK/DJF (142.51 ± 41.39). No significant difference was found with regard to dual-energy X-ray absorptiometry measurements, age, or body mass index between patients who did and did not develop DJK/DJF. Conclusions: Patients who developed DJK/DJF had significantly lower computed tomography-measured HU as compared to those without DJK/DJF. Our findings highlight the potential importance of BMD evaluation with computed tomography prior to multilevel spine fusion surgery, though further research would be helpful to evaluate the significance of dual-energy X-ray absorptiometry-based BMD measurements on DJK/DJF development.