A Systematic Review of Metal Composite Bone Grafts in Preclinical Spinal Fusion Models

Successful arthrodesis is a crucial factor in spinal fusion surgery, maximizing the likelihood of improved quality of life. The incorporation of metals into bone grafts has been demonstrated to enhance fusion rates through various osteoinductive and osteoconductive pathways. A systematic review was conducted to investigate the utility of metal composite bone grafts in promoting arthrodesis in spinal fusion preclinical studies. PubMed/MEDLINE was queried to identify studies investigating metal composite bone grafts in animal models of spinal fusion. Non-spinal fusion animal models were excluded. Risk of bias was assessed using the SYRCLE risk of bias tool. After screening a total of 1554 articles, 17 articles were included in our review. Metal composite bone grafts with bioactive agents had significantly greater fusion rates than metal composite only bone grafts (p < 0.001) and similar fusion rates compared to non-metal comparator bone grafts (p = 0.172). Bone grafts containing strontium and magnesium had the greatest fusion rates compared to other metals and had significantly greater fusion rates than those of silicon-containing bone grafts (p = 0.02 and p = 0.04, respectively). Bone quality and bone volume percentages of fusion masses formed by metal composite bone grafts were enhanced via the addition of bioactive agents such as stem cells, rhBMP-2, autograft, and poly (lactic-co-glycolic acid). The adverse event rate was 3.0% in all animal surgeries. Metal composite bone grafts show promise as osteoinductive agents to promote arthrodesis in spinal fusion, and their osteoinductive capability is enhanced with the synergistic addition of osteogenic factors such as stem cells and autograft.