Bio-lubricant Properties Analysis of Drilling an Innovative Design of Bioactive Kinetic Screw into Bone

Abstract

Biotribology is applied to study the friction, wear, and lubrication of biological systems or natural phenomena under relative motion in the human body. It is a multidisciplinary field and tribological processes impact all aspects of our daily life. Tribological processes may occur after the implantation of an artificial device in the human body with a wide variety of sliding and frictional interfaces. Blood is a natural bio-lubricant experiencing laminar flow at the lower screw velocities associated with drilling implants into bone, being a viscoelastic fluid with viscous and fluid characteristics. The viscosity comes from the blood plasma, while the elastic properties are from the deformation of red blood cells. In this study, drilling parameters according to material properties obtained by Finite Element Analysis are given. The influence of blood on the resulting friction between the surfaces is demonstrated and correlated with mechanical and biological consequences, identifying an innovative approach to obtaining a new lubricant parameter for bone drilling analysis. The lubrication parameter (HN) found within the limitations of conditions used in this study is 10.7 × 10−7 for both cortical bone (D1) and spongy bone (D4). A thermal-structural analysis of the densities of the soft bone (D4) and hard bone (D1) shows differences in only the equivalent stress values due to the differences in respective Young moduli. The natural occurrences of blood as a lubricant in bone-screw perforations are poorly investigated in the literature and its effects are fundamental in osseointegration. This work aims to elucidate the relevance of the study of blood as a lubricant in drilling and screwing implants into bone at lower speeds.