Biomechanical Evaluation of Augmentation of Osteoporotic Cancellous Bone with an Injectable Nano-hydroxyapatite/ Polyamide 66 Composite Cement

A new injectable biomimetic composite cement composed of nano-hydroxyapatite (n-HA) and polyamide 66 (polyhexamethylene adipamide) has been developed. This study investigated that in vitro biomechanical performances of three n-HA/PA composite cements in the augmentation of osteoporotic cancellous bone were different in various n-HA content to evaluate the clinical applicability. The thoracic vertebrae and femoral condyles of five osteoporotic and one normal cadaver were utilized to divide into five groups: 60wt%, 70wt%, 80wt%, the osteoporotic and the normal groups. The thoracic vertebrae performed by vertebroplasty were loaded in compression until 75 percent of vertebral height. The cancellous bone specimens made of femoral condyles were applied to torsional testing. Biomechanical testing showed the compressive and torsional performances in the groups injected with 60%, 70% and 80% n -HA/PA composite cement increased markedly than that in osteoporosis. Some of the mechanical parameters were close to normal cancellous bone, in particular, 70% group in compressive properties and 60% group in torsional properties. This study demonstrated that the injectable n-HA/PA composite cement was capable of strengthening the compressive and torsional properties of osteoporotic cancellous bone and suggested that 60% and 70% cement might be competent materials in the treatment and prophylaxis of osteoporotic fracture.