Validation of Innovative Method of Murine Vertebral Compression Testing

Murine vertebral compression testing is a common technique to quantify trabecular bone biomechanics. Having a precise method of vertebral compression is important for aiding researchers in making clinically relevant discoveries in musculoskeletal research. While many methods exist in literature, there has yet to be established a universal protocol for this procedure. Many challenges exist in vertebral compression, such as the irregular shape of the vertebral body (trabecular region of interest), uneven endplate surface morphology, and surrounding cortical processes. Therefore, the aim of this study was to develop a new method of vertebral compression that accounts for these factors and to validate this procedure using vertebrae from a prior disease/treatment study that produced groups with significant differences in bone properties. A murine diabetic nephropathy model was induced through a combination of streptozotocin injections (STZ) and adenine-laced casein diets (Ad). The first group (STZ-Ad) received 100 μL subcutaneous vehicle injections (phosphorus buffered saline, PBS) per day, and the second group (Romo) received the same PBS injections and Romososumab (10 mg/kg) weekly. At 24 weeks of treatment, mice were euthanized. L5 vertebrae were isolated and specialized endcaps were developed from epoxy to form-fit caudal and cranial vertebral endplates, accounting for surface topography and preserving the original structure of the vertebrae. Vertebrae were preloaded to 0.5 N and compressed to failure at a rate of 0.025 mm/s with maximum displacement of 4 mm. Ultimate force and ultimate displacement were recorded. Post-compressed vertebrae were scanned using microcomputed tomography (μCT), reconstructed (NRecon), rotated (Data Viewer), and visualized for fracture damage (Drishti). A significant difference was detected between groups for ultimate force (p = 0.0012); no significant difference was found for ultimate displacement. These results indicate that this novel method of vertebral compression can accurately identify significant differences in trabecular biomechanics, aiding in musculoskeletal research.