Bone is the second most commonly transplanted tissue in the world

with at least four million surgical procedures using bone grafts and bone substitutes every year. However

the limitations of traditional treatments have affected current treatment options

and the clinical demand for bone grafts has continued to increase due to the high incidence of trauma

cancer

infection

and arthritis. Autografts and allografts are commonly used in the clinical treatment of bone defects

but chronic inflammation

disease transmission

and immune rejection have hindered their development. In addition

metal-based material scaffolds are the most widely used implants

while there are also problems such as stress shield

infection

and inflammation

leading researchers to find new material scaffolds to replace them. Therefore

developing bioactive three-dimensional (3D) scaffolds that can be adaptively expanded and filled to promote bone regeneration has become a key area of focus in bone tissue engineering (BTE). In recent years

manufacturing methods including 4D printing of shape memory materials have been used to create new methods to replace traditional bone grafts. This paper mainly reviews the classification of traditional polymer materials and new shape memory polymer materials

the main manufacturing methods

mechanical properties

biocompatibility

and the latest applications of polymer scaffolds in BTE. Furthermore

the importance

current challenges

and future development directions of 4D printing technology in BTE are summarized.