Implant design and its effects on osseointegration over time within cortical and trabecular bone. 
Healing chambers present at the interface between implant and bone have become a target for improving osseointegration.  The objective of the present study was to compare osseointegration of several implant healing chamber configurations at early time points and regions of interest within bone using an in vivo animal femur model.  Six implants, each with a different healing chamber configuration, were surgically implanted into each femur of six skeletally mature beagle dogs (n = 12 implants per dog, total n = 72).  The implants were harvested at 3 and 5 weeks post-implantation, non-decalcified processed to slides, and underwent histomorphometry with measurement of bone-to-implant contact (BIC) and bone area fraction occupied (BAFO) within healing chambers at both cortical and trabecular bone sites.  Microscopy demonstrated predominantly woven bone at 3 weeks and initial replacement of woven bone by lamellar bone by 5 weeks.  BIC and BAFO were both significantly increased by 5 weeks (p < 0.001), and significantly higher in cortical than trabecular bone (p < 0.001).  The trapezoidal healing chamber design demonstrated a higher BIC than other configurations.  Overall, a strong temporal and region-specific dependence of implant osseointegration in femurs was noted.  Moreover, the findings suggest that a trapezoidal healing chamber configuration may facilitate the best osseointegration.  © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1091-1097, 2016.