Intermittent weekly administration of human parathyroid hormone (1–34) improves bone-hydroxyapatite block bonding in ovariectomized rats

Hydroxyapatite (HA) blocks have been widely used for the reconstruction of bone defects and as a bone substitute. Bone-implant bonding depends on both implant-related factors and patient variables. Intermittent human parathyroid hormone (h-PTH) has a strong anabolic effect on bone formation. The purpose of the present study is to evaluate whether intermittent h-PTH administration enhances bone-HA block bonding in normal versus ovariectomized (OVX) rats. Cancellous bone osteotomy and HA-block implantation were performed on the proximal left tibia in both OVX and sham-operated 7-month-old female Sprague-Dawley rats. Newly formed cancellous bone around the HA block and bone-HA block bonding were evaluated by bone histomorphometry at 8 weeks after the administration of h-PTH (100 μg/kg/week) or its vehicle. The administration of h-PTH significantly increased cancellous bone volume by stimulating bone formation in OVX rats (p < 0.01). Although bone-HA block bonding was significantly decreased in OVX rats compared to that of sham-operated rats (p < 0.01), h-PTH improved the bone-HA block bonding in OVX rats (p < 0.01). These results suggest that intermittent h-PTH treatment may improve bone-HA bonding in osteoporosis by restoring cancellous bone volume and enhancing cancellous bone formation around the HA block.