ABSTRACT【Introduction】The present investigation assessed the influence of romosozumab, a recently introduced medication in Japan, on the early bone fusion process in a rat posterolateral lumbar fusion (PLF) model. We aimed to overcome the limitations of a previous study by utilizing a higher dosage, which was 19 times greater than the clinical equivalent, to investigate the efficacy of lower dosages of romosozumab for promoting bone healing using the same rat lumbar PLF model. 【Methods】A total of 24 male 8-week-old Sprague–Dawley rats underwent PLF surgery and were divided into four groups according to the dosage of romosozumab administered postsurgically: the standard dose used in prior studies, half and one-tenth of this dose, and a control group. We administered romosozumab bi-weekly for 8 weeks based on the rats’ body weights. Assessments included bi-weekly micro-computed tomography (CT) scans and histological examinations of the lumbar spine performed 8 weeks post-surgery. 【Results】CT analysis revealed no significant differences in bone fusion rates and volume increases among the romosozumab groups at various time points post-surgery, but all showed significantly higher values than those in the control group. Histological evaluation confirmed these findings, with the romosozumab groups exhibiting significantly greater trabecular area ratios at the PLF site than the controls. 【Conclusions】Romosozumab effectively promotes early bone fusion at all tested dosages, including one-tenth of previously used amounts, indicating its efficacy at significantly lower doses. These findings suggest the potential clinical use of romosozumab at lower, more practical doses for enhancing bone fusion.
Toshi et al. (2025) studied this question.