Preliminary In Vivo Studies of a New Injectable Bone Substitute

Calcium-phosphate materials have been increasingly employed in orthopedic and dental applications in recent years and are now being developed for use in noninvasive surgery or as carriers for drug delivery systems. We developed an injectable bone substitute (IBS) for percutaneous orthopedic surgery which uses a biphasic calcium-phosphate (BCP) mixture composed of hydroxyapatite (60%) and /Hricalcium phosphate ( 40% ), together with a polymer (hydroxy-propyl-methyl-cellulose, HPMC) as a carrier. The best BCP/polymer ratio was determined to achieve the highest mineral phase in the composite and provide the rheological properties required for injectable material. The in vivo biocompatibility and biofunctionality of ms were tested in rabbits using implants in subcutaneous, intramuscular and cartilage sites and defects created in trabecular bone of the femur epiphysis. The defects were filled with IBS, and histological studies were performed after 1, 2, 4 and 12 weeks on decalcified and non-decalcified sections. Image analysis and backscattered electron analyses were performed by scanning electron microscopy. This study demonstrated that HPMC is a non-toxic material which can be associated with calcium-phosphates to produce an IBS and create a matrix for deep cell colonization conducive to bone ingrowth.