By adding IGF and TGF-β to HA-coated cages in a goat cervical fusion model, Gu et al. found the cage with IGF and TGF-β had significantly higher tensile strengths in extension and scoliosis compared to the other groups, indicating that they achieved better spinal fusion (Gu et al., 2013). This evidence concerns the gene IGF1 and scoliosis.