EFFECTS OF PARATHYROID HORMONE (PTH) (1–34) TREATMENT ON THREE-DIMENSIONAL MICROSTRUCTURAL PROPERTIES OF REGENERATED BONE AFTER DISTRACTION OSTEOGENESIS IN A RABBIT TIBIAL LENGTHENING MODEL. A MICRO-TOMOGRAPHIC IMAGING STUDY.

Abstract

Since the approval of parathyroid hormone (PTH) as an anabolic treatment for osteoporosis, PTH has increasingly been investigated for other potential clinical uses such as bone repair and regeneration. The microstructure of newly formed bone during distraction osteogenesis enhanced by PTH treatment has yet to be studied. Therefore, the purpose of the study was to investigate the effects of intermittent parathyroid hormone PTH (1–34) treatment on the microstructure of regenerated bone during distraction osteogenesis in rabbits. After tibial mid-diaphyseal osteotomy the callus was distracted 1 mm/day for 10 days. The rabbits were divided in to 3 groups, which daily received a PTH injection for 30 days, a saline injection for 10 days and a PTH injection for 20 days, or a saline injection for 30 days. The new-trabecular structure of the regenerate callus was assessed by micro computed tomography (μCT). In all 51 specimen obtained from the lengthened tibia were scanned and evaluated morphometrically using three different volume of interests. The investigated μCT parameters included trabecular number Tb.N*, trabecular thickness Tb.Th*, trabecular separation Tb.Sp*, bone volume fraction (BV/TV), bone volume (BV), connectivity density (CD), and degree of anisotropy (DA). The results showed that intermittent treatment with PTH during distraction osteogensis resulted in a significantly higher Tb.N*, a more isotropic trabecular orientation, a higher connectivity density, and a higher bone mass. We also found preliminary evidence suggesting that the newly regenerated calluses treated with PTH were more mature than the non-treated calluses. In conclusion: the study demonstrated that treatment with PTH resulted in an enhanced microstructure of the newly regenerated bone indicating that PTH has a potential role as a stimulating agent for distraction osteogenesis.