Injectable Calcium phosphate material in a critical size def
Bone graft substitutes made of calcium phosphate are used to speed up the repair of bony defects induced by trauma or surgery. The authors report an injectable calcium phosphate-based bone void filler that has been specifically designed with hyaluronic acid to provide a longer working period for ease of injection into bony deficiencies that are difficult to access during minimally invasive surgery.

The bone substitute material deliverability and physical properties were characterized, and in vivo response was evaluated in a critical size distal femur defect in skeletally mature rabbits to 26weeks. The interface with the host bone, implant degradation, and resorption were assessed with time.

--The calcium phosphate bone substitute material could be injected as a paste within the working time window of 7–18min, and then self-cured at body temperature within 10min.

--The material reached a maximum ultimate compressive strength of 8.20 ± 0.95MPa, similar to trabecular bone.

--The material was found to be biocompatible and osteoconductive in vivo out to 26weeks, with new bone formation and normal bone architecture observed at 6weeks, as demonstrated by histological evaluation, microcomputed tomography, and radiographic evaluation.

In conclusion, the material characteristics and performance are well suited for minimally invasive percutaneous delivery applications, according to these findings.