## 5 Conclusions  
The assessing of conventional PM and space holder technique reported here allowed for stating some findings about the influence on both microstructural and mechanical properties of porous Ti for bone replacement:  
1. [PERSON]'s modulus of porous Ti samples could be reached close enough to the cortical bone by conventional PM (29 GPa), in the absence of the compaction pressure stage (loose-sintering technique), with a sintering temperature of 1000 \({}^{\circ}\)C, and 2 h under high vacuum. However, the mean pore size (\(\sim\)17 \(\upmu\)m) and the mechanical strength (\(\sim\)67 MPa) of the porous titanium do not guarantee the mechanical requirements of biomedical applications. Both increments of compaction pressure and sintering temperature improve the quality of the sintering necks, which imply decreasing of the amount and the size of the pores; consequently, the stiffness is increased (\(\geq\)50.5 GPa) and the capability of bone ingrowth.  
2. The space-holder method is the more suitable of the two evaluated routes to reach a biomechanical balance (\(E\) and \(\sigma_{y}\)) and biofunctional equilibrium (bone ingrowth), through the control of the processing parameters, the type of space holder, the compaction pressure and the sintering temperature, according to viability, feasibility and implementation costs in the industrial sector, in  
Figure 5: Uniaxial compression tests: (**a**) [PERSON]’s modulus closed to the cortical bone is set in \(\sim\)29 GPa (porosity total range between 37.6–44.8%); (**b**) yield strength values are fixed in a range (150–200 MPa) meeting the requirements of the cortical tissue. Compression stress vs. Strain curves of specimens manufactured by different PM routes.  
addition to the achievement of the desirable balance. The use of NH\({}_{4}\)HCO\({}_{3}\) as space holder (40 vol.% and \(\sim\)200-300 \(\upmu\)m mean particle size distribution) is recommended. The optimal manufacturing parameters proposed are the following ones: firstly, a compaction pressure of 600 MPa, next, in the space-holder elimination stage, 60 \({}^{\circ}\)C for 10 h plus 110 \({}^{\circ}\)C for 12 h in vacuum (10\({}^{-2}\) mbar) and sintering conditions at 1250 \({}^{\circ}\)C, for 2 h and high vacuum (10\({}^{-5}\) mbar). These parameters ensure the production of porous titanium where the stress-shielding phenomenon is reduced, and suitable mechanical strength and bone ingrowth are achieved.  
All of the authors have contributed to obtaining a high-quality research work. [PERSON] has been responsible for the experimental results and analysis of data, [PERSON] and [PERSON] performed analysis of the results and writing the original draft, [PERSON] was responsible of finite element analysis, [PERSON] and [PERSON] have been responsible for materials and processing techniques selection, funding acquisition and project administration, [PERSON] was responsible for the fabrication processes and the discussion of the results.  
This work was supported by the Ministry of Economy and Competitiveness of Spain under Grant MAT2015-71284-P, Junta de Andalucia under Grant No. P12-TEP-1401 and the funding provided by the Comision Nacional de Investigacion, Cientifica y Tecnologica (CONICYT) of the Chilean government under the project FONDECYT 11160865.  
The authors dedicate this paper to the memory of [PERSON] (University of Antioquia, Colombia) for his valuable contribution in the metal biomaterials field, being a pioneer in this sector and an honourable researcher in the group that has performed this work. The authors wish to thank the laboratory technicians [PERSON] and [PERSON] [PERSON], [PERSON] and [PERSON] for carrying out the microstructure characterization and mechanical testing.  
The authors declare no conflict of interest.