Implantable Devices for Bone Regeneration: Generating Fluid Flow Independent of Compression to Promote Bone Growth

Abstract

All cells display the incredible ability to detect external stimuli, such as mechanical stress, and convert those stimuli into biochemical signals and subsequent cellular responses. In bones, a type of bone cell called osteocytes are the main conductors of this mechanotransduction. Osteocytes reside in spaces called lacunae and are connected by channels called canaliculi. Gravitational pull, bearing weight, and muscle contraction all cause small deformations of our bones and thus cause interstitial fluid movement through the lacunar-canalicular network. Osteocytes, which are connected by cytoplasmic processes, communicate these mechanical stresses and translate them into cellular mechanisms that augment the bone mass in the area of the stress. Typical therapies for bone fractures include stabilization and mechanical loading. However, in instances where fractures are severe and a significant section of bone is lost, this mechanical loading is not a feasible therapy. Therefore, in the Ong Lab, we are looking at ways to directly induce this fluid shear stress at a gap fracture site to study the role of fluid flow in bone regeneration and enhance the rate of bone healing in instances of severe fractures. There are numerous ways to induce fluid shear stress, but our research uses magnetohydrodynamics. This method involves combining a magnetic field with a perpendicular electrical field from cathode and anode electrodes powered by a power supply. The combination of these fields generates a force that acts on charged particles, driving them in a direction perpendicular to both the electric and magnetic fields. Previous benchtop and in vitro experiments have demonstrated that the device successfully induces fluid flow. Moreover, the magnitude of the force on the conductive fluid can be altered by changing the electrical or magnetic field strength. We have also conducted three in vivo pilot studies in Wistar rats, which have generally produced data in support of the hypothesis that the device induces fluid movement in the fracture site and enhances bone growth in that area. The device and technology thus may offer applications in the clinical sphere as a novel therapy for bone regeneration.