Hydroxyapatite (HA) macrochanneled porous scaffolds were produced by polymer sponge templating method using a reactive submicrometer powder synthesized by hydroxide precipitation sol–gel route. The microstructure of the fine HA powder was carefully investigated and developed in order to optimize the mechanical properties and phase stability of sintered scaffold. The templating method ensured a highly interconnected macrochanneled porous structure with over 500 μm mean pore size and 90% porosity. The high reactivity of the powder led to an efficient sintering mechanism with a high and crack-free linear shrinkage (19 ± 2%) and a significant BET specific surface area reduction (from 12 to 0.33 m2/g). The powder does not dissociate into secondary phases during sintering. Despite the extreme porosity, the scaffolds had high mechanical performance (compressive strength ∼0.51 MPa, Weibull modulus 4.15) compared with literature data and with scaffolds similarly prepared from high-quality commercial HA powder.