In vivo bone regeneration with injectable calcium phosphate biomaterial:: A three-dimensional micro-computed tomographic, biomechanical and SEM study

This in vivo study investigated the efficiency of all injectable calcium phosphate bone substitute (IBS) for bone regenerative procedures through non-destructive three-dimensional (3D) micro-tomographic (mu CT) imaging, biomechanical testing with a nondestructive micro-indentation technique and 2D scanning electron microscopy (SEM) analysis. The injectable biomaterial was obtained by mixing a biphasic calcium phosphate (BCP) ceramic mineral phase and a cellulosic polymer. The BCP particles were 200-500 mu m or 80-200 mu m in diameter. The injectable material was implanted for 6 weeks into critical-sized bone defects Lit the distal end of rabbit femurs. Extensive new bone apposition was noted with both 2D and 3D techniques. Micro-CT showed that newly formed bone was in perfect continuity with the trabecular host bone structure and demonstrated the high interconnectivity of the restored bone network. For both IBS formulations, SEM and mu CT gave very close measurements. The only detected significant difference concerned the amount of newly formed bone obtained with IBS 80-200 that appeared significantly higher with mu CT analysis than with SEM (p = 0.00007). Student t-tests did not show any significant difference in the amount of newly formed bone and remaining ceramic obtained from mu CT analysis or SEM. Regression analysis showed satisfactory correlation between both the amount of newly formed bone and remaining ceramic obtained from mu CT or SEM. For IBS 200-500, the newly formed bone rate inside the defect was 28.0 +/- 5.2% with SEM and yield strength of the samples was 18.8 +/- 5.4 MPa. For IBS 80-200, the newly formed bone rate inside the defect was 31.7 +/- 5.1 % with SEM and yield strength of the samples was 26.8 +/- 4.5 Wa. Yield strength appeared well correlated with the amount of newly formed bone, specially observed with mu CT. This study showed the ability of non-destructive techniques to investigate biological and mechanical aspects of bone replacement with injectable biomaterials. (c) 2005 Elsevier Ltd. All rights reserved.