Table 1 Questions for quality assessment based on the Downs and Black checklist [23] and the STROBE statement [24]

1

Is the scientific background/rationale for the investigation reported?

2

Is the aim/objective of the study clearly described?

3

Is the porosity design method clearly described?

4

Is the rationale of the porosity design clearly described?

5

Is the study design clearly described?

6

Is the study design suitable to validate the porosity design with regard to stress shielding?

7

Are the outcome measures suitable to validate the porosity design with regard to stress shielding?

8

Are the outcome measures reliable?

9

Are the outcomes and main findings of the study clearly described?

10

Are the key results clearly stated regarding the study objectives?

11

Are the limitations of the study discussed?