In this work, we propose a convenient non-catalytic method for modifying hydroxyapatite (HA) with lactic acid to obtain a composite material suitable for traumatology fasteners. The affinity of the modified HA for the polylactide matrix increases, which has a positive effect on the composite mechanical properties. The modification process is carried out with lactic acids solutions in ethanol. It was shown that hydroxyapatite modified with 10–30% solutions retains its structure according to IR spectroscopy and X-ray diffraction analysis, and when modified with a 50% solution, calcium hydrophosphate is formed. Studies of the mechanical properties have shown that the modulus increases by almost 1 GPa for composites with modified HA compared to unmodified hydroxyapatite reaching a value close to that of native cortical bone tissue.