Studies to improve bone augmentation procedures using injectable biomaterials

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There are currently no effective therapies for Vertebral Fractures VF, the most common complications of osteoporosis. The mortality rate associated with VF is reported to be 8%. Since the VF incidence is expected to escalate as the population ages, it is essential to find solutions. Bone augmentation is a novel procedure to treat bone fractures. In it, a self-hardening cementitious polymethyl methacrylate PMMA, percutaneously injected into the porous structure of the bone. The PMMA, once hardened, stabilizes the fractured bone. The main benefit is that the patient experiences relief from pain, almost immediately after the procedure, at a fraction of the cost of other surgical treatments. The research program is delineated in 3 projects to address 3 major challenges of the procedure. The 1st challenge is the mismatch of the stiffness of the hardened PMMA cement and bone, causing high stresses in the adjacent bone. Higher stresses can lead to new adjacent damage or migration of the PMMA. The 1st objective is to aerate the viscoelastic PMMA paste, with sterile air, to reduce this mismatch. Specifically, the air-containing mixture produces porous cement and its stiffness can be adapted by the percentage of contained air. The solution, considering the issue of new materials facing regulatory challenges, resides in a mixing device. Calcium phosphate CP is a material recently introduced to address the biological shortcoming of PMMA. Yet, CP comes with new injection problems. The 2nd objective is to vibrate and fluidize the CP particle paste to prevent the suspending liquid phase from separating from the CP particle paste, which results in a non-uniform CP paste extrudate. As a result of the vibrofluidization, the liquid and paste may remain percutaneously injectable and the extrudate homogeneous. The 3rd challenge is the inability of physicians to intraoperatively evaluate the trabecular bone strength, which largely defines the vertebral strength and stability of transpedicular screws that are essential for anchoring a multi-component mechanical construct in the osteoporotic spine. The decision is made subjectively whether or not to augment the transpedicular screws. The 3rd objective is to develop a percutaneous indentation process, in which the trabecular bone is considered as a porous solid, and to use a rigid probe to objectively measure its strength. The research program comprises both computational and experimental methods to effectively study the physical and geometric interactions in the 3 objectives. The expected outcomes will be 3 novel medical technologies: a piezo-instrumented syringe, an aeration mixer, and a bone strength probe to reliably screen patients for osteoporosis. The prime beneficiaries are patients suffering from bone fractures. The socioeconomic impact of these developments is potential health care savings and commercial exploitation of devices by the medical industry.