4D printing strategy helps fabricate biomimetic microchannel scaffold for spinal fusion Spinal fusion is frequently performed to restore spinal stability in patients with spinal diseases, such as spinal stenosis, vertebral fractures, progressive deformities, and instability. In the past two decades, there has been marked increase in the number of people over 65 years in age who have needed spinal fusion surgery. While autogenous bone grafts have long been considered the reference standard for spinal fusion, painful pseudoarthrosis remains a leading cause of poor clinical outcomes. Many researchers have consequently focused on trying to create a biomimetic scaffold that induces vascularization to enable bone tissue regeneration and spinal fusion.