Quantitative analysis of the resorption and osteoconduction process of a calcium phosphate cement and its mechanical effect for screw fixation.

ABSTRACT

The clinical application of calcium phosphate cements (CPCs) composed of tetracalcium phosphate and dicalcium phosphate anhydrous has been limited because of its longer setting time, so that we developed the CPC in which the setting time was shortened to approximately 10 min. Aiming at clinical application, we evaluated the histological response in the bone quantitatively and the biomechanical effectiveness of this substance. The CPC was implanted in the rabbit femoral condyle up to 52 weeks for histological evaluation. In mechanical testing, small cancellous screws were inserted into the condyle, both with and without augmentation with the CPC, and the pull-out strength was measured. The micro-computed tomography finding demonstrated that the cross-sectional area of the implanted CPC at 24 weeks was approximately two-thirds of the initial area. The amount of newly calcified bone around the CPC was significantly greater than that of the sintered hydroxyapatite. Histologically, the new bone was formed on the surface of the implanted CPC 1 week after the implantation and resorption of the CPC was evident at 3 weeks. The pull-out strength was enhanced significantly by augmentation with the CPC and the initial strength was maintained for a 6 week period. This CPC showed good osteoconductivity and was resorbed without adverse inflammation. Using the CPC as augmentation may be capable of useful treatment options in fractures with poor bone quality.