Evaluation of testosterone and alendronate coated membranes in osteoporotic fracture and defect model in rats and goats.

Background: Osteoporotic fractures present significant clinical challenges with associated risk of non-union. This study evaluates the efficacy of testosterone and alendronate-coated collagen membranes in accelerating osteoporotic fracture healing using rat and goat models. Methods: Female Sprague-Dawley rats with ovariectomy-induced osteoporosis (n = 90) and ovariectomized Chinese mountain goats (n = 20) were assigned to treatment and control groups receiving either testosterone/alendronate-coated or control membranes at fracture or defect sites. Rats were euthanized at weeks 2, 4, and 8, and goats at days 30 and 60 post-operation. Assessments included radiographs, micro-CT, histology, immunohistochemistry, mechanical testing, and finite element analysis. Results: In rats, the Ovariectomy (OVX)-Coated Membrane group exhibited significantly greater callus width at weeks 2, 4, and 8 compared to OVX-No Membrane (p < 0.01) and OVX-Control Membrane groups (p < 0.05). Callus area was 135 % larger at week 4 compared to control (p < 0.05). Micro-CT showed a 50 % increase in low-density bone volume (p < 0.05) and significant increases in high-density bone volume at week 8 (p < 0.01). Mechanical testing revealed a 20 % higher ultimate load (p < 0.05) and 35 % greater energy to failure (p < 0.001) in the treatment group. Immunohistochemistry demonstrated a 30 % increase in VEGF expression and a significant elevation in osteoblast numbers at early time points (p < 0.05). Serum testosterone levels were significantly elevated in treated rats at week 2 (p < 0.05) (Fig.5A). In goats, no significant differences in callus parameters were observed at day 30. However, by day 60, the OVX-Coated group showed a 24 % greater callus width (p < 0.05), 135 % larger callus area , and 19 % higher callus index. Micro-CT analysis revealed a significant increase in high-density bone volume (p < 0.01), BV/TV (p < 0.01), and trabecular number (p < 0.05).Mechanical testing indicated a trend toward higher ultimate load. Finite element analysis showed a 28 % more uniform stress distribution and significantly lower deformation under 800 N load, suggesting enhanced biomechanical stability. Histology confirmed increased trabecular bone formation, collagen fiber proliferation, and osteoclast activity at day 60 (Fig.5B). Conclusion: These findings suggest that testosterone and alendronate-coated collagen membranes significantly accelerate osteoporotic fracture healing by promoting angiogenesis, osteoblast activity, and balanced bone remodeling. Early effects are evident in rodents, with later but robust healing in large animal models. The translational potential of this article: The dual anabolic and antiresorptive strategy enhances bone quality and mechanical strength, supporting its potential clinical translation for improving osteoporotic fracture healing.