Aim:An important objective of spinal fusion surgery is the solid fixation of the spinal segment; however, the pseudoarthrosis rate ranges between 5 and 43%. Human adipose-derived stem cells (h-ADSCs) have been demonstrated to induce osteogenesis in spine fusion models. This study evaluated the efficacy of h-ADSCs in spinal fusion in an osteoporotic rat model.Material and Methods:Female Sprague-Dawley rats (n = 40) underwent ovariectomy and were then randomly assigned into two groups: ovariectomy (OVX) (OVX + fusion) and h-ADSCs (OVX + fusion + h-ADSCs). Six weeks after OVX, we performed bilateral lumbar spinal fusion using the autologous iliac bone with or without administration of h-ADSCs. The efficacy of the spinal fusion was then assessed using manual palpation, lateral ending, morphogenic examinations, and histology six weeks the after fusion procedure. Results:Fusion bed volume was different between the two groups but not significantly. However, the fusion bed density was higher in the h-ADSC group than in the OVX group. Manual palpation (70% vs. 40%, p = 0.112) and lateral bending (95% vs. 55%, p = 0.011) produced higher fusion rates in the h-ADSC group than in the OVX group. Additionally, a histologic examination revealed new bone formation at the fusion bed between the lamina and implanted iliac crest bone in the h-ADSC group, whereas, in the OVX group, the fusion masses were composed of fibroblastic proliferation.Conclusion:Our study demonstrates that the administration of h-ADSCs may have advantages in bone formation and consolidation but does not lead to bone overgrowth. These findings indicate that the administration of h-ADSCs is an alternative and efficient method for spinal fusion.