Effect of systemic parathyroid hormone (1-34) and a beta-tricalcium phosphate biomaterial on local bone formation in a critical-size rat calvarial defect model.

P>Objective The objective of this study was to evaluate local bone formation following systemic administration of parathyroid hormone (1-34) (PTH), a surgically implanted synthetic beta-tricalcium phosphate (beta-TCP) bone biomaterial serving as a matrix to support new bone formation. Materials and Methods Critical-size, 8 mm, calvarial through-and-through osteotomy defects were surgically created in 100 adult male Sprague-Dawley rats. The animals were randomized into five groups of 20 animals each to receive one of the following treatments: PTH (15 mu g PTH/kg/day; subcutaneously), PTH/beta-TCP, beta-TCP, or particulate human demineralized freeze-dried bone (DFDB), and sham-surgery controls. Ten animals/group were euthanized at 4 and 8 weeks post-surgery for radiographic and histometric analysis. Results The histometric analysis showed that systemic PTH significantly enhanced local bone formation, bone fill averaging (+/- SE) 32.2 +/- 4.0% compared with PTH/beta-TCP (15.7 +/- 2.4%), beta-TCP (12.5 +/- 2.3%), DFDB (14.5 +/- 2.3%), and sham-surgery control (10.0 +/- 1.5%) at 4 weeks (p < 0.014). Systemic PTH showed significantly enhanced bone formation (41.5 +/- 4.0%) compared with PTH/beta-TCP (22.4 +/- 3.0%), beta-TCP (21.3 +/- 4.4%), and with the sham-surgery control (23.8 +/- 4.2%) at 8 weeks (p < 0.025). The DFDB group showed significantly increased bone formation from 4 (14.5 +/- 2.3%) to 8 weeks (32.0 +/- 3.2%) (p < 0.006). The PTH/beta-TCP and beta-TCP groups both showed limited biomaterials resorption. The radiographic analysis was not diagnostic to distinguish local bone formation from the radiopaque beta-TCP biomaterial. Conclusions Systemic administration of PTH significantly stimulates local bone formation. Bone formation was significantly limited by the beta-TCP biomaterial.