Bone union and strength effect of Romosozumab: An imaging and mechanical study using a rat posterolateral lumbar fusion model

Abstract In this study, we investigated the effect of romosozumab on bone strength at the fusion site in rats that underwent posterolateral lumbar fusion. For bone grafting, autogenous bone was harvested from the spinous process and grafted between the intervertebral joint and transverse processes of the 4th, 5th, and 6th lumbar vertebra bilaterally along with 40 mg of demineralized bone matrix. Rats were matched by body weight and divided equally into R (romosozumab, 25 mg/kg) and C (control, saline) groups. Subcutaneous injections were administered twice a week until 10 weeks post-operation. Computed tomography was performed 10 weeks post-operation to measure bone fusion rate, fused bone volume, and bone density. The fused area bone strength was also measured using 3-point bending. Results showed that group R rats had significantly higher bone fusion zone volume, bone mineral density, and bone strength than group C rats. Thus, the results demonstrated that romosozumab administration not only promoted osteogenesis at the bone graft site but also affected bone strength. Conclusion We demonstrated that romosozumab administration not only promoted osteogenesis at the bone graft site but also affected bone strength.