Three-dimensional microstructural properties of regenerated mineralizing tissue after PTH (1-34) treatment in a rabbit tibial lengthening model

Since the approval of parathyroid hormone (PTH) as treatment for osteoporosis, PTH has increasingly been investigated for bone repair and regeneration. The aim of the study was to investigate the effects of intermittent PTH treatment on the microstructure of regenerated mineralizing tissue after distraction osteogenesis in rabbits. After tibial mid-diaphyseal osteotomy the callus was distracted 1 mm/day for 10 days. 72 rabbits were divided in to 3 groups, which daily received a PTH (1-34) 25 microg/kg 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 microstructure of the regenerate was assessed by micro computed tomography (microCT). In all 51 obtained specimens were evaluated morphometrically using three different volumes of interests. The results showed that treatment with PTH during distraction osteogenesis resulted in a significantly higher trabecular number, a more isotropic trabecular orientation, a higher connectivity density, and a higher mineralizing tissue mass. We also found that distraction calluses treated with PTH were more mature than the non-treated. Conclusion: treatment with PTH resulted in an enhanced microstructure of the newly regenerated mineralizing tissue indicating that PTH has a potential role as a stimulating agent during distraction osteogenesis.