Investigating the Effect of Denosumab on Bone Density in Patients with Osteoporosis

Introduction: Osteoporosis, characterized by decreased bone mineral density (BMD), significantly impacts quality of life in the elderly population. Conventional osteoporosis treatments (e.g. bisphosphonates) improve BMD relatively slowly, providing limited benefits for many patients undergoing spine surgery. Denosumab, a human monoclonal antibody against RANKL that inhibits osteoclast differentiation, has shown promising results for the treatment of osteoporosis in patients unresponsive to bisphosphonates.

Methods: This retrospective cohort study analyzed 40 female patients with a diagnosis of osteoporosis. The two cohort groups were (I) patients treated with denosumab and (II) patients treated with alendronate starting in 2012-present. Patients were matched based on age, duration of treatment, and pre-treatment t-score. The primary outcome of bone mineral density (BMD) was measured before and after starting treatment using: (a) T-scores at the femoral neck from DXA scans, (b) BMD measurements at the left hip from DXA scans and (c) Hounsfield units (HU) at the L1 vertebra determined by CT scan.

Results: Patients in the denosumab group showed a significant increase in BMD as measured by HU at the L1 vertebra from baseline (6.93%, p< 0.01*), while patients treated with alendronate showed a significant decrease in L1 HU from baseline (-9.77%, p< 0.05*). The difference in the mean % change in L1 Hounsfield Units between the two cohorts was significant (p < 0.01*).

Both cohorts showed a modest increase in mean T-score at the femoral neck that did not reach significance (6.38%, p=0.098 for denosumab vs. 5.72%, p=0.20 for alendronate). The denosumab treatment group showed no significant change in mean BMD measurement at the left hip compared to baseline (0.39%, p=0.42), while the patients in the alendronate group showed a small decrease in mean BMD measurement at the left hip that did not reach significance (-0.60%, p=0.44).

Conclusion : This study demonstrates that denosumab treatment significantly improves BMD at the L1 vertebra in patients with osteoporosis compared to baseline and alendronate treatment. We conclude that denosumab represents a promising treatment option for patients with osteoporosis undergoing spine surgery due to its effects demonstrated at the L1 vertebra.