A Composite of Polymethylmethacrylate, Hydroxyapatite, and -Tricalcium Phosphate for Bone Regeneration in an Osteoporotic Rat Model

The purpose of this study was to test several modifications of the polymethylmethacrylate (PMMA) bone cement by incorporating osteoconductive and biodegradable materials for enhancing bone regeneration capacity in an osteoporotic rat model. Three bio-composites (PHT-1 [80% PMMA, 16% HA, 4% beta-TCP], PHT-2 [70% PMMA, 24% HA, 6% beta-TCP], and PHT-3 [30% PMMA, 56% HA, 14% beta-TCP]) were prepared using different concentrations of PMMA, hydroxyapatite (HA), and beta-tricalcium phosphate (beta-TCP). Their morphological structure was then examined using a scanning electron microscope (SEM) and mechanical properties were determined using a MTS 858 Bionics test machine (MTS, Minneapolis, MN, USA). For in vivo studies, 35 female Wister rats (250 g, 12 weeks of age) were prepared and divided into five groups including a sham group (control), an ovariectomy-induced osteoporosis group (OVX), an OVX with pure PMMA group (PMMA), an OVX with PHT-2 group (PHT-2), and an OVX with PHT-3 group (PHT-3). In vivo bone regeneration efficacy was assessed using micro-CT and histological analysis after injecting the prepared bone cement into the tibial defects of osteoporotic rats. SEM investigation showed that the PHT-3 sample had the highest porosity and roughness among all samples. In comparison to other samples, the PHT-3 exhibited favorable mechanical properties for use in vertebroplasty procedures. Micro-CT and histological analysis of OVX-induced osteoporotic rats revealed that PHT-3 was more effective in regenerating bone and restoring bone density than other samples. This study suggests that the PHT-3 bio-composite can be a promising candidate for treating osteoporosis-related vertebral fractures.