TABLE 5.

The constraints required to be considered in the design of the bone scaffolds.

Constraint type	The constraint	References
Biological constraint	Connectivity of the microstructure	Heinl et al. (2008)
	Porosity of the scaffold no less than 50%
	pore size should be larger than 0.05 mm and less than 0.8 mm
Mechanical constraint	Close to the modulus of the surrounding tissue	Wang et al. (2016)
	The anatomic loading requirements should be met
Additive manufacturing constraint	Structure thickness no less than 0.2 mm if the SLM is used	Arabnejad et al. (2016)
	The minimal hanging angle should be larger than a set threshold value	Zhang et al. (2019)