The Effect of Biocomposite Screws on Bone Regeneration in a Rat Osteoporosis Model.

Abstract

To evaluate the efficacy of biocomposite screws used in ovariectomy (OVX)-induced osteoporotic rats. Twenty-four female Wistar rats (250-300 g, 12 weeks old) were divided into 4 groups: sham group (control), OVX-induced osteoporosis group (OVX), OVX and biodegradable poly(lactic-co-glycolic acid) (PLGA) without tricalcium phosphate (β-TCP) screw insertion group (OVX/BSR), and OVX and biocomposite (PLGA with β-TCP) screw insertion group (OVX/CSR). Three groups underwent bilateral OVX, and of these, 2 groups had 2 different types of screw inserted at the proximal tibia. At 25 weeks after OVX, the bilateral tibias were extracted. The extracted tibiae were scanned by ex vivo micro-computed tomography (CT) and stained with hematoxylin and eosin (H&E) and with Masson's trichrome stain for pathological assessment. Compared with the ovariectomized groups, the control group had the highest values for bone mineral density (BMD), bone volume (BV)/total volume (TV), and trabecular number (Tb.N) and the lowest values for trabecular thickness (Tb.Th) and trabecular separation (Tb.Sp). In the pairwise comparison among ovariectomized groups, the OVX/CSR group had significantly higher BMD, BV/TV, and Tb.N values than the other 2 groups (OVX and OVX/BSR) and significantly lower Tb.Sp. Micro-CT scans showed clear evidence of new trabecular formation near the screw insertion site in the OVX/CSR group only. Analyses of H&E- and Masson's trichrome-stained sections showed more and thicker trabecular bone around the implant in the OVX/CSR group compared with the OVX and OVX/BSR groups. Biocomposite screws can improve local bone quality and facilitate osteoconductivity in an osteoporotic rat model.