Development and Evaluation of a Modified Injectable Calcium Phosphate Cement with Enhanced Injectability and Mechanical Stability for Bone Defect Repair

An injectable carbonated hydroxyapatite (ICHA) bone cement with improved rheology and injectability was developed for minimally invasive orthopedic applications and evaluated in distal radius fracture fixation. Carbonated hydroxyapatite cement was optimized with 2% hydroxypropyl methylcellulose (HPMC) after screening six additives, producing a formulation with favorable injectability and controlled setting. A human cadaveric distal radius fracture model was stabilized using Kirschner wires (K-wires), ICHA alone, or ICHA plus K-wires, followed by torsional and compressive testing. Within a 10° torsional range, the ICHA and ICHA + K-wire groups showed significantly higher torsional stiffness and maximum torque than K-wires alone (P < 0.01), with smaller maximum torsion angles (4–5° vs. 9.5°, P < 0.05), indicating superior rotational stability. Although compressive stiffness did not differ significantly, compressive strength at 2 mm displacement and peak compressive strength were markedly higher in ICHA-containing groups (P < 0.01). ICHA cement also demonstrated reliable injectability and stable setting. Overall, ICHA provides enhanced mechanical stability and handling properties, supporting its potential for minimally invasive fracture fixation and bone defect repair.